How to tell intake and exhaust valve with the intake manifold on?
BSAKing
it out and one of the rocker arms was quite loose.
I am reading up on how to set the clearance on the lifters. I snag #1
cyl and get it at TDC using the marks on the flywheel. I can tell the
cyl # by the stamp on the engine block. Then I can set certain exhaust
and intakes to proper clearance. No problem since all the cylinder
numbers are marked on the head.
1. BUT how do I tell which is exhaust and which is the intake valve
with the intake manifold on? Been looking in the book and I see no
info on that.
Then I move and set it for #6 cyl and then do the rest of the rocker
settings.
2. Been wondering how come that rocker was so loose. As I understand
it, the hydraulic lifter is just an oil filled damper chamber to take
up erratic slackness within fine limits. If it was stuck it would make
a clicking noise, but would not be THAT loose? Or do I misunderstand?
thx BSA
willy
> I had a heck of a noise going on in my 350 V8 chevy engine. I checked
> it out and one of the rocker arms was quite loose.
>
> I am reading up on how to set the clearance on the lifters. I snag #1
> cyl and get it at TDC using the marks on the flywheel. I can tell the
> cyl # by the stamp on the engine block. Then I can set certain exhaust
> and intakes to proper clearance. No problem since all the cylinder
> numbers are marked on the head.
>
> 1. BUT how do I tell which is exhaust and which is the intake valve
> with the intake manifold on? Been looking in the book and I see no
> info on that.
Each intake rocker will be lined up with an intake manifold "runner".
Each exhaust rocker will be lined up with the an exhaust manifold
"runner". "Runner" being the part of the intake manifold that the air/
fuel mixture travels through to get to the cylinder, or the part of
the exhaust manifold the exhaust ravels through to get out of the
cylinder.
An easier way is, starting at the front of the engine and going to the
back, they are laid out like this on both sides: EIIEEIIE E+ exhaust
I=intake
The best way to adjust them is to do it when the engine is hot and
adjust them while the engine is "running". Back off the adjuster nut
until you hear a tapping sound. Slowly tighten the nut until the
tapping stops. Tighten the nut a quarter of a turn at a time to a
total of a "half" of a turn, not a "full" turn as a lot of books say.
A full turn is to tight. Also go only a "half" of a turn if you're
doing it with the engine off.
Oil will fly when doing it running. One of these will help:
> 2. Been wondering how come that rocker was so loose. As I understand
> it, the hydraulic lifter is just an oil filled damper chamber to take
> up erratic slackness within fine limits. If it was stuck it would make
> a clicking noise, but would not be THAT loose? Or do I misunderstand?
>
Few reasons rockers will come lose on a small block. 1) Collapsed
lifter or one that won't pump up all the way. 2) Worn cam lobe. 3)
Rocker stud pulling out of the head. 4) Rocker cutting into the side
of the rocker stud (usually from a worn rocker and/or rocker ball.5)
Bent push rod.
Vic Smith
wrote:
You normally don't have to adjust hydraulic lifter valve lash after
the initial adjustment.
Try some Sea Foam or something else made to free stuck lifters before
you horse around with this.
You could have a bad lifter(s) or flattened cam lobe(s).
I put cams and new lifters in a Ford 352 and a Chevy 350.
Used the method below, and never adjusted rockers with the engine
running. No problems.
Start at TDC #1 and work around the valves in firing order per the
instructions below.
Zero lash means when the pushrod stops turning freely in your fingers
as you tighten down the rocker.
You should be able to find a picture to sort out intake from exhaust.
I think the exhaust is on the left as you face the head, but find a
picture.
Think hard about what you're doing, and what the actual problem is.
I've got the feeling you're wasting your time.
http://www.hotrodders.com/forum/valve-lash-adjustment-52345.html
"Hold the phone!! Everyone cover their toes cause I am about to start
stomping...... We have covered this many times. Chiltons is a piss
poor way to set lash as is the method with the engine running. The
only proper way to set lash is one cylinder at a time when the engine
is on the stand before it is fired. You set the exhaust valve when the
intake valve opens and has about half closed and the intake valve as
the exhaust starts to open. What this does is insure that the valve is
on the back side of the lobe opposite the ramp. Using chiltons method
you have some valves that are actually starting to open. This is
especially true for engines with agressive cam profiles. Using the
running method you either beat the piss out of the BRAND NEW cam while
it is breaking or you let it idle while you set the valves....either
is bad.
If you set the valves properly one cylinder at a time you can go
1/4-1/4 turn past zero lash and you are set from now on. I never take
the valve covers off of an engine once I have cranked it unless
something is wrong and have never had an issue with not having the
valves set properly.
Chris"
--Vic
Steve W.
> I had a heck of a noise going on in my 350 V8 chevy engine. I checked
> it out and one of the rocker arms was quite loose.
>
> I am reading up on how to set the clearance on the lifters. I snag #1
> cyl and get it at TDC using the marks on the flywheel. I can tell the
> cyl # by the stamp on the engine block. Then I can set certain exhaust
> and intakes to proper clearance. No problem since all the cylinder
> numbers are marked on the head.
>
> 1. BUT how do I tell which is exhaust and which is the intake valve
> with the intake manifold on? Been looking in the book and I see no
> info on that.
With the valve cover off this is VERY easy. Take a look at the exhaust
manifold. Notice how there are three sections that bolt to the head?
They are almost exactly in line with the exhaust valves. One on each end
and two in the middle.
>
> Then I move and set it for #6 cyl and then do the rest of the rocker
> settings.
>
> 2. Been wondering how come that rocker was so loose. As I understand
> it, the hydraulic lifter is just an oil filled damper chamber to take
> up erratic slackness within fine limits. If it was stuck it would make
> a clicking noise, but would not be THAT loose? Or do I misunderstand?
A bad lifter can collapse and cause the rocker to become very loose. It
also will NOT repair itself. You need to actually open the engine up and
replace/repair the bad lifter. It could also mean that the cam lobe has
ground down. The way to check that is with a dial indicator. You place
it on a good rocker for the same valve (intake for intake and exhaust
for exhaust) and see how far it travels then put it on the ? one and see
how far that one moves, it should move almost exactly the same amount
(almost because you will have some differences depending on the
lifter/lobe wear)
Another item on SBCs is that on the older engines with press in rocker
studs they can pull out of the head over time, causing a loose rocker
and then you need to reinstall it and pin it OR use a screw in stud
conversion kit.
>
> thx BSA
--
Steve W.
Steve Austin
> I had a heck of a noise going on in my 350 V8 chevy engine. I checked
> it out and one of the rocker arms was quite loose.
>
> I am reading up on how to set the clearance on the lifters. I snag #1
> cyl and get it at TDC using the marks on the flywheel. I can tell the
> cyl # by the stamp on the engine block. Then I can set certain exhaust
> and intakes to proper clearance. No problem since all the cylinder
> numbers are marked on the head.
>
> 1. BUT how do I tell which is exhaust and which is the intake valve
> with the intake manifold on? Been looking in the book and I see no
> info on that.
>
jim
You may have a bad camshaft. What year is the engine?
-jim
>
> thx BSA
BSAKing
When I tightened the other rockers - it was only a smidgen - like
maybe 1/8 turn at most just take a bit of slop out - some I actually
loosened a tad. Just to get them sounding quite similar with just a
'little' noise on each thru a garden hose. (I know - I can hear the
purists and experts cringing... lol, but I did not know any better)
That one noisy one though I had to turn a bit and now you have me
worried. lol.
I think I'll get some Sea Foam and run it through - it may loosen that
one and then I can re-adjust. All I can say is that from the limited
bit that I drove it - it was a lot smoother for sure....
It is a 1976 corvette l-48 350 smogger - with about 125K miles on it.
Never been opened up. FWIW, I usually do my own oil changes and I have
never seen any metal grounds or debris in it.....
I'll try the loosening route first with Sea Foam (it sounds like a
highly recommended product from what I read on the web) - if no go,
then I guess I will have to gird my loins and pull the intake
manifold. I am just a weekend mechanic and have never done any heavy
duty engine work, so let's try the obvious first - that seems to make
the most sense.
Thanks for all the great info - REALLY helpful!
BSA
jim
BSAKing wrote:
>
> Hi - all this great info has given me food for thought.
>
> When I tightened the other rockers - it was only a smidgen - like
> maybe 1/8 turn at most just take a bit of slop out - some I actually
> loosened a tad. Just to get them sounding quite similar with just a
> 'little' noise on each thru a garden hose. (I know - I can hear the
> purists and experts cringing... lol, but I did not know any better)
>
> That one noisy one though I had to turn a bit and now you have me
> worried. lol.
>
> I think I'll get some Sea Foam and run it through - it may loosen that
> one and then I can re-adjust. All I can say is that from the limited
> bit that I drove it - it was a lot smoother for sure....
>
> It is a 1976 corvette l-48 350 smogger - with about 125K miles on it.
> Never been opened up. FWIW, I usually do my own oil changes and I have
> never seen any metal grounds or debris in it.....
Bad cams were common in that era - although you would think the bad ones
would have been weeded out by now.
If it is the cam lobe worn down you should be able to see that valve not
moving as much as the others. And if it is a bad cam the clacking will
be back fairly soon - they wear pretty fast once they start.
Changing the cam is not that hard and they should still be some
available in junk yards.
-jim
willy
> Changing the cam is not that hard and they should still be some
> available in junk yards.
>
> -jim
LMAO. You are kidding, right?!?! You do not get a cam from a junk
yard! Get a new one. Plenty around. If it comes to that, get an RV cam
or one above the stock cam. 125K, you should change the timing chain
anyway.
That Tune
news:tuadnS_iQcOhuwLQ...@bright.net...
>
> BSAKing wrote:
>>
>> Hi - all this great info has given me food for thought.
>>
>> When I tightened the other rockers - it was only a smidgen - like
>> maybe 1/8 turn at most just take a bit of slop out - some I actually
>> loosened a tad. Just to get them sounding quite similar with just a
>> 'little' noise on each thru a garden hose. (I know - I can hear the
>> purists and experts cringing... lol, but I did not know any better)
>>
>> That one noisy one though I had to turn a bit and now you have me
>> worried. lol.
>>
>> I think I'll get some Sea Foam and run it through - it may loosen that
>> one and then I can re-adjust. All I can say is that from the limited
>> bit that I drove it - it was a lot smoother for sure....
>>
>> It is a 1976 corvette l-48 350 smogger - with about 125K miles on it.
>> Never been opened up. FWIW, I usually do my own oil changes and I have
>> never seen any metal grounds or debris in it.....
>
> Bad cams were common in that era - although you would think the bad ones
> would have been weeded out by now.
> If it is the cam lobe worn down you should be able to see that valve not
> moving as much as the others. And if it is a bad cam the clacking will
> be back fairly soon - they wear pretty fast once they start.
>
> Changing the cam is not that hard and they should still be some
> available in junk yards.
>
> -jim
Someone that can't dsitinguish an intake from an exhaust
valve sure as hell shouldn't attempt changing a camshaft.
jim
Those cams tended to fail because of manufacturing defects. The ones
that didn't have the defective hard facing would outlast the rest of the
engine.
Any cam you find in the junk yard for this engine will be either like
new or junk. It's pretty easy to spot the difference.
-jim
willy
>
> Someone that can't dsitinguish an intake from an exhaust
> valve sure as hell shouldn't attempt changing a camshaft.
Just because he doesn't know the layout of the valves is not a reason
for him to not tackle putting a cam in. Sorry the rest of us didn't
come out of the womb as a rocket scientist, like you evidently did.
willy
>
> Those cams tended to fail because of manufacturing defects. The ones
> that didn't have the defective hard facing would outlast the rest of the
> engine.
>
> Any cam you find in the junk yard for this engine will be either like
> new or junk. It's pretty easy to spot the difference.
>
> -jim
Your telling me it makes sense to take the time to pull cams in yards
in hopes of finding a good one? Your telling me a yard is gona let you
take apart a good engine? Your telling me you would buy a good engine
from a yard, take it home and rip the cam out of it to put in another
engine? All that work and what do you have? You still have a used cam
and lifters when your done. And speaking of lifters, you gotta keep
them matched up with each lope. Guess your gona tell him to use the
timing chain that came out of the yard also?!?! Cam and lifters for
small blocks are not expensive. For christ sakes use your head!
willy
>
> You may have a bad camshaft. What year is the engine?
>
> -jim
What does knowing the year of the engine have to do with diagnosing a
bad cam?!?!
I have a 300hp 350. It doesn't run right. It's a 1969. Can you tell me
whats wrong with it? lol
hls
"willy" <dancesw...@embarqmail.com> wrote in message
news:9bd97d82-0304-4126...@u8g2000yqh.googlegroups.com...
******
I think what he was getting to was that some years and models of
engine have known problems with cam wear, lifter stud slippage,
etc.
The OP's symptoms COULD come from a bad cam lobe, but that
is not the only thing that would cause his problem.
At least, that was the way I interpreted his post.
jim
You are guessing it would be difficult. I've stuck several bone yard
cams in small block chevys.
He can buy a new cam and lifters if he wants to spend the money, but
the engine isn't likely to last any longer.
-jim
BSAKing
Where I am now is that I took the most logical route and that was to
stuff some Sea Foam in it. I also cleaned up the ignition to see if it
would cure some of the roughness.
I have only done a few miles in it. There is a still valve noise, but
it "seems" a little less severe. I will drive it for a bit and then
pop off that valve cover again and check to see how far down the nut
is WRT to the others and touch up the adjustments as best I can based
on the info here and see where we are then. I think the nut travel was
much the same from recollection, so it may be at the end of the day
that It will only need adjusting after the Sea Foam does it's work.
Time will tell I guess. That's the best, at the worst new cam, etc.
Moderate would be new lifters... but one step at a time.
I note the dissertation about cam shafts. Always an unpleasant
possibility, but it actually runs a little better now, so I have my
fingers crossed.
If I do have to go to the trouble, I certainly would not put in a used
cam, lifters, or timing chain - I mean what's the point of that? The
differential in the cost of those parts (used vs new) is far offset by
the time and effort involved. AFAIK those parts are readily available
new.
Keep you posted.
BSA
PS. "someone that can't dsitinguish an intake from an exhaust valve
sure as hell shouldn't attempt changing a camshaft. " - You could very
well be right, and I probably would not tackle it because of time and
equipment. But please don't mistake unfamiliarity with stupidity. (at
least I am not afraid to ask, and I do know how to spell
"distinguish"). lol.
Vic Smith
wrote:
New cams and lifters were pretty cheap when I did mine.
I wouldn't buy any worn mechanical part from a boneyard unless I could
mike it to new specs.
Besides, this stuff has a tendency to snowball.
On an old engine if you replace a cam, you start thinking about the
cam bearings. Then the mains and crank seals.
On my 352 I decided to do it all at the beginning, because I had the
desire and energy,
Big job if you DIY unless you're half machinist and have a good shop.
I had my garage floor and rented an engine hoist.
I took the crankcase, crank, rods and pistons to what they used to
call a "speed shop" around here.
They tanked the crankcase, polished the crank, miked everything,
installed the cam bearings, and sold me the cam and bearings that fit
their miking. Think the cam had a bit more lift.
About 30 bucks IR. But that's 1975 dollars.
Mains were different than original because of crank wear and
polishing. Rings were different than original due to bore wear.
I did the ridge reaming and bore polishing myself.
Heads were reworked at another shop.
It all came together fine except the head shop screwed up the guides
or seals so I was sucking some oil.
Not too bad and I lived with that. Just pissed me off.
Probably had $12-1500 hundred in parts and shop work.
And a whole lot of labor by me.
It's a serious endeavor unless you really enjoy doing it.
I don't regret it, but once was enough.
My 350 had the about the same miles as the OP, maybe less.
Hard to say since it was a rebuilt. Found the sticker on the
crankcase. A major rebuilder but I can't remember the name.
This was about 1990.
A valve went bad so I pulled the heads, took them to a shop.
The shop told me one of the heads was a 305 and recommended
they get a boneyard 350 head and work that.
Anyway that all went okay. I put new lifters in.
Cost maybe $500 total and a lot of labor from me.
Three months later a rod started knocking and I junked it.
Rust was overcoming it anyway.
My bottom line now for valve train or lower end issues is either junk
it or buy a crate engine if you want to keep the car.
But I don't really trust rebuilts either, since I had a bad one.
I had my mech put a Targetmaster 307 crate engine in my son's car
about then years ago, but that's a new engine with a good warranty.
As soon as you start pulling heads for anything but a gasket you've
got a good chance of going backwards moneywise.
That's just my view. Usually rust has almost destroyed a car here
before an engine becomes an issue.
A fiberglass Vette is a different issue.
Should be answers on a Vette forum.
I hope that Sea Foam works for the OP. I've freed up sticky lifters
on old V-8's before. Think I used "Engine Flush" products.
Those were beaters, and I'm not recommending that.
Not even sure about the Sea Foam.
Think I used it for injectors once, Didn't work.
I needed new injectors.
You can find all kind of stories on the internet.
--Vic.
Vic Smith
wrote:
>Well - I have been reading the updates here.
>
>Where I am now is that I took the most logical route and that was to
>stuff some Sea Foam in it. I also cleaned up the ignition to see if it
>would cure some of the roughness.
>
>I have only done a few miles in it. There is a still valve noise, but
>it "seems" a little less severe.
Don't recall how you located the noise and whether this applies.
But one time I was *sure* I heard a bad or stuck lifter.
When I examined the sound up close I found it was a leaking
exhaust donut gasket.
--Vic
That Tune
news:20e2f257-e881-48d6...@k11g2000yqc.googlegroups.com...
There wasn't the slightest implication of stupidity, although
after reading your latest complaint (quite apparently you're also
wholly unable to recognize the incorrectly sequenced letters in
an obvious typo), in addition to your original plea for help (and
advising a novice not to tackle a camshaft replacement on an
SBC without available, onsite, experienced assistance, IS in
fact help of the first order), I can readily understand how and
why you might very justifiably and understandably be senstive.
about an issue of competence.
But if in fact your otherwise empty, miserable existence is so
conspicuously impoverished, wanting and devoid of actual
meaning that for it to afford you any value whatsoever you
desperately resort to cruising newsgroups (while solciting
assistance, no less) for perceived errors in spelling, grammar,
diction or punctuation (therewith providing your sole raison
d'etre), in a pathetically feeble attempt at mocking those that
would strongly discourage you from making a likely critical
error, far be it from me to deny you that crucial perquisite ;^)
Best of luck to you, given your approach and personality,
you're going to sorely require all you can possibly muster.
jim
BSAKing wrote:
>
> If I do have to go to the trouble, I certainly would not put in a used
> cam, lifters, or timing chain - I mean what's the point of that?
The point would be to save some money and frankly I suspect that unless
you are willing to pay somebody who is competent to rebuild this engine
you are probably not going to end up with a nice running engine no
matter what you do. So I suggest not spending too much money on this
'learning experience'. Since either way you will likely end up with more
or less the same result.
I Personally put 200k additional miles on a cam pulled from a SBC
engine. The donor engine was said to be worn out (burned oil).
Using aggressive solvents dumped into the crankcase will often do more
harm than good. If you want to clean out a sludged-up engine just change
the oil and filter every 100 miles until it is clean.
-jim
BSAKing
> "BSAKing" <bsak...@gmail.com> wrote in message
OMG! Touchy are we....? And totally unable to understand an ironic
comment it seems. That's ok - we all have our days. You may also want
to look up the definition of "lol" in internet shorthand...
In any event, to everyone else, thank you for taking the time to
answer my request for information and advice. It is most helpful and
appreciated.
If it is a major rebuild, it is certainly beyond my capability and
desire - I would be the first to admit it. If it does fall into that
camp, on a 35 year old engine I note the comments from another poster
and I could see it being a bottomless pit with a very hard to justify
cost-benefit. Not sure what the heck I would do then...
The most I would have any desire or capability to address is some easy
component replacement and/or adjustment. I am going to remove the
valve covers again and re-examine and try to adjust everything armed
from info from here and the service manual. I'll see where that gets
me. I would hate to relegate old Betsy to the bone yard after having
had her for 35+ years, so wish me luck.
I will LYK how I make out.
BSA
That Tune
********
You may rest assured in the most certain knowledge that I've
forgotten, yet still retain, more about Computer Systems and
Sciences than you're ever going to have the slightest inkling
about.
In any event, to everyone else, thank you for taking the time to
answer my request for information and advice. It is most helpful and
appreciated.
If it is a major rebuild, it is certainly beyond my capability and
desire - I would be the first to admit it. If it does fall into that
camp, on a 35 year old engine I note the comments from another poster
and I could see it being a bottomless pit with a very hard to justify
cost-benefit. Not sure what the heck I would do then...
The most I would have any desire or capability to address is some easy
component replacement and/or adjustment. I am going to remove the
valve covers again and re-examine and try to adjust everything armed
from info from here and the service manual. I'll see where that gets
me. I would hate to relegate old Betsy to the bone yard after having
had her for 35+ years, so wish me luck.
I will LYK how I make out.
BSA
****
Here's a little more assistance that you can desperately use:
Just leave the damned thing alone before you cause substantial
bodily injury (or worse) to yourself or other unfortunate innocent
victims in the vicinity.
BSAKing
A possibility most certainly, but highly unlikely. thanks for your
comments.
jim
>
> The most I would have any desire or capability to address is some easy
> component replacement and/or adjustment. I am going to remove the
> valve covers again and re-examine and try to adjust everything armed
> from info from here and the service manual. I'll see where that gets
> me. I would hate to relegate old Betsy to the bone yard after having
> had her for 35+ years, so wish me luck.
In case your statement is genuine.
The mostly likely component that has failed on your engine is the
vacuum advance on the distributor. If after 35 years the diaphragm is
still intact it would be a minor miracle. The difference a working
vacuum advance is rather subtle because it only functions when the
engine is under light loads. But a defective vacuum advance will over
time cause all sorts of engine damage including the type of problems you
are having.
Get one at a parts store or on ebay:
http://tinyurl.com/5rtxtea
-jim
BSAKing
A very astute observation Jim! Thanks - and it is the original as I
really have had the car since day #1. It certainly should be replaced
as a preventative measure. I'll look into sourcing a repladcement as
part of all of this.
Ed Treijs
This thread just makes me roll my eyes, in so many different ways.
The vacuum advance diaphram is hardly 'the most likely thing to fail'
on an old engine. Furthermore, if it fails, it will typically spring a
leak. No vacuum advance will hardly make the cam go bad. If the
centrifugical advance mechanism has seized up--and I have had this
happen to me--then the engine might be running at full advance all the
time, which is not good. However, again it won't do squat to the cam.
A '76 Corvette has value, even if the engine has some issues. The
obvious choices are: 1) Fix the engine up properly; 2) Hope that
driving and an oil change or two will more or less fix things; 3) Make
sure all ancillary vacuum lines, plug wires, etc. are in good shape,
pull the distributor cap to make sure everything looks good, and put
on a timing light to ensure that timing is right, and vacuum and
centrifugical advance are functioning properly; 4) Sell the car for
some pretty good money to someone who wants a '76 Corvette.
Choice 4) is pretty final....if your car is in decent shape, and you
still like driving it, then 1) would be a better choice.
As for finding a cam in a junkyard, this is a 350 Chevy flat-tappet
hydraulic cam. The aftermarket is huge and cheap for 350 Chevies.
We're talking a nice car, not some junker hillbilly pickup. Get a new
cam.
Ed Treijs
> 3) Make
> sure all ancillary vacuum lines, plug wires, etc. are in good shape,
> pull the distributor cap to make sure everything looks good, and put
> on a timing light to ensure that timing is right, and vacuum and
> centrifugical advance are functioning properly;
I just want to make clear that this choice has nothing to do with
fixing or not fixing a noisy valvetrain. It's a general check for a
smog engine. The vacuum lines can crack; lubricant can dry up, etc.
Also, don't discount an exhaust gasket leak as the real culprit. Does
it get less noisy as the engine warms up? Leaks tend to do that.
jim
Ed Treijs wrote:
>
> This thread just makes me roll my eyes, in so many different ways.
>
> The vacuum advance diaphram is hardly 'the most likely thing to fail'
> on an old engine.
Who said it was the most likely thing to fail?
It is however extremely likely to have failed once in 35 years. That
probability is getting pretty close to 100%. If he still has the
original tires on this car it would be likely that they would have
failed by now, also. And any other rubber component on this car is
likely to fail after 35 years.
The failure of the vacuum advance will cause the engine to deteriorate.
The vast majority worn out 350 engines made in the 70's wore out because
the vacuum advance diaphragm started to leak. The reason is simple -
mechanics never bothered to check the the vacuum advance and the effects
of a non-functioning vacuum advance doesn't show up as an immediate loss
of power or performance but instead take its insidious toll on an engine
over 10k - 20K miles or more.
>Furthermore, if it fails, it will typically spring a
> leak. No vacuum advance will hardly make the cam go bad.
How do you know the cam has gone bad?
> If the
> centrifugical advance mechanism has seized up--and I have had this
> happen to me--then the engine might be running at full advance all the
> time, which is not good. However, again it won't do squat to the cam.
That is a very suspicious statement. How the heck can mechanical advance
seize up in the full advance position? It would be a real challenge to
get it to stick in the advanced position even if you wanted it to stick
in that position
Typically when the mechanical advance seizes it is due to rust. And it
develops rust while sitting still. That means it always seizes in the
full retard position.
Vic Smith
wrote:
>
>
>Ed Treijs wrote:
>
>>
>> This thread just makes me roll my eyes, in so many different ways.
>>
>> The vacuum advance diaphram is hardly 'the most likely thing to fail'
>> on an old engine.
>
>Who said it was the most likely thing to fail?
>
> It is however extremely likely to have failed once in 35 years. That
>probability is getting pretty close to 100%. If he still has the
>original tires on this car it would be likely that they would have
>failed by now, also. And any other rubber component on this car is
>likely to fail after 35 years.
>
> The failure of the vacuum advance will cause the engine to deteriorate.
>The vast majority worn out 350 engines made in the 70's wore out because
>the vacuum advance diaphragm started to leak. The reason is simple -
>mechanics never bothered to check the the vacuum advance and the effects
>of a non-functioning vacuum advance doesn't show up as an immediate loss
>of power or performance but instead take its insidious toll on an engine
>over 10k - 20K miles or more.
>
You can hardly not know if your vacuum advance is bad on a 350.
Same with all the Ford and GM V-8's I worked on with a manifold vacuum
advance.
You time it with the vacuum disconnected from the dist and plugged.
When you reconnect it revs up.
If you're curious you'll check the advance with your light before you
set your idle. Goose it to see the mechanical advance.
Whether you check it or not, if the advance is bad, I think you'll
have noticeable performance problems.
Although I never had a bad one, I did always check when I did a tune
up.
Hard to believe pro mechs don't do the same. Part of a tune-up.
--Vic
jim
Vic Smith wrote:
>
> You can hardly not know if your vacuum advance is bad on a 350.
> Same with all the Ford and GM V-8's I worked on with a manifold vacuum
> advance.
If it was manifold vacuum that would be an older engine.
> You time it with the vacuum disconnected from the dist and plugged.
> When you reconnect it revs up.
That would not be for a '76. By then they had ported vacuum so the
advance doesn't kick in until you stepped on the gas. So connecting the
vacuum at idle should have no affect. On the older engines with points
there was also the window in the cap for adjusting points - so you could
see inside to see the distributor plate advance.
> If you're curious you'll check the advance with your light before you
> set your idle. Goose it to see the mechanical advance.
> Whether you check it or not, if the advance is bad, I think you'll
> have noticeable performance problems.
No there are no noticeable performance issues (at least not for the
first 5k-10k miles). The advance works only under lighter loads. So if
you accelerate hard it behaves the same whether the advance is
functioning or not.
> Although I never had a bad one, I did always check when I did a tune
> up.
So how much advance were you looking for and how did you go about
measuring it?
> Hard to believe pro mechs don't do the same. Part of a tune-up.
After electronic ignition - ignition tune-ups were mostly changing spark
plugs. The base timing maybe was checked. And as you pointed out, the
procedure for checking the timing is with the advance disconnected.
-jim
>
> --Vic
Vic Smith
wrote:
>
>
>Vic Smith wrote:
>
>>
>> You can hardly not know if your vacuum advance is bad on a 350.
>> Same with all the Ford and GM V-8's I worked on with a manifold vacuum
>> advance.
>
>If it was manifold vacuum that would be an older engine.
>
>
>> You time it with the vacuum disconnected from the dist and plugged.
>> When you reconnect it revs up.
>
>That would not be for a '76. By then they had ported vacuum so the
>advance doesn't kick in until you stepped on the gas. So connecting the
>vacuum at idle should have no affect. On the older engines with points
>there was also the window in the cap for adjusting points - so you could
>see inside to see the distributor plate advance.
>
Forgot that ported vacuum. My 350's were a '76 and '78.
Probably my '66 352 was the one with manifold vacuum.
I think they all had the window in the cap for dwell adjustment.
My '64 Bug didn't have a window, but I could use a continuity light
and feeler gauge for timing and dwell.
>
>> If you're curious you'll check the advance with your light before you
>> set your idle. Goose it to see the mechanical advance.
>> Whether you check it or not, if the advance is bad, I think you'll
>> have noticeable performance problems.
>
>No there are no noticeable performance issues (at least not for the
>first 5k-10k miles). The advance works only under lighter loads. So if
>you accelerate hard it behaves the same whether the advance is
>functioning or not.
>
>
>> Although I never had a bad one, I did always check when I did a tune
>> up.
>
>So how much advance were you looking for and how did you go about
>measuring it?
>
Don't remember how many degrees. I always had specs for all this and
followed the book. Best I can recall is goose to maybe 3 grand on the
tach and see maybe 30-40 on the mark.
It wasn't precise as I recall, since it jumped around.
Just checking that the mech advance was in the ballpark.
Lower and steady for the vacuum, maybe 1200 and 12-16 on the mark.
That's just my recollection, probably bad.
I don't think I ever ran a 350 more than 5 years before the car/van
under it rusted out. But I tuned them every year. Plugs, wires,
points, choke. They never failed me.
Until the van 350 developed a rod knock.
Not a fan of the 350, but the vehicles were bought cheaply and served
me well enough.
>
>> Hard to believe pro mechs don't do the same. Part of a tune-up.
>
>After electronic ignition - ignition tune-ups were mostly changing spark
>plugs. The base timing maybe was checked. And as you pointed out, the
>procedure for checking the timing is with the advance disconnected.
>
I checked timing on my first electronic ignition engine, a 2.8, in
'91 when I bought the car. Habit I suppose.
My tach/dwellmeter and timing light haven't been used since.
I'm just fine with that.
--Vic
Ed Treijs
> Ed Treijs wrote:
>
> > This thread just makes me roll my eyes, in so many different ways.
>
> > The vacuum advance diaphram is hardly 'the most likely thing to fail'
> > on an old engine.
>
> Who said it was the most likely thing to fail?
Well:
On Apr 12, 5:15 pm, jim <"sjedgingN0Sp"@m...@mwt.net> wrote:
....
> The mostly likely component that has failed on your engine is the
> vacuum advance on the distributor. If after 35 years the diaphragm is
> still intact it would be a minor miracle. The difference a working
> vacuum advance is rather subtle because it only functions when the
> engine is under light loads. But a defective vacuum advance will over
> time cause all sorts of engine damage including the type of problems you
> are having.
>
> Get one at a parts store or on ebay:http://tinyurl.com/5rtxtea
>
> -jim
It appears that you did. Why are you asking about what you wrote a day
or two earlier?
> It is however extremely likely to have failed once in 35 years. That
> probability is getting pretty close to 100%. If he still has the
> original tires on this car it would be likely that they would have
> failed by now, also. And any other rubber component on this car is
> likely to fail after 35 years.
The original vacuum advance canister, the heat riser vacuum motor, and
the vacuum choke breaks on the carburetor of my '78 Pontiac all work
fine. Apparently my car is the Miracle Shrine of Lourdes. Tell you
what, I'll check the state of the vacuum advance canisters on the old
Chevy and Buick HEIs I have lying around at home. They're original
from the late '70s.
> The failure of the vacuum advance will cause the engine to deteriorate.
> The vast majority worn out 350 engines made in the 70's wore out because
> the vacuum advance diaphragm started to leak. The reason is simple -
> mechanics never bothered to check the the vacuum advance and the effects
> of a non-functioning vacuum advance doesn't show up as an immediate loss
> of power or performance but instead take its insidious toll on an engine
> over 10k - 20K miles or more.
Please explain exactly what the effects of the failed vacuum advance
are on 1) the engine's functioning; and 2) on the car's driveability.
Then explain the causal mechanism by which a failed vacuum advance
causes the engine to 'deteriorate'?
> >Furthermore, if it fails, it will typically spring a
> > leak. No vacuum advance will hardly make the cam go bad.
>
> How do you know the cam has gone bad?
We don't. However, you jumped in by saying 1) "Get a new cam from the
junkyard", followed by 2) "A bad vacuum advance is a horrible thing".
I assume you were linking the bad advance to the possibly bad cam. Or
are you just saying whatever comes in your mind, relevant or not?
> > If the
> > centrifugical advance mechanism has seized up--and I have had this
> > happen to me--then the engine might be running at full advance all the
> > time, which is not good. However, again it won't do squat to the cam.
>
> That is a very suspicious statement. How the heck can mechanical advance
> seize up in the full advance position? It would be a real challenge to
> get it to stick in the advanced position even if you wanted it to stick
> in that position
> Typically when the mechanical advance seizes it is due to rust. And it
> develops rust while sitting still. That means it always seizes in the
> full retard position.
1. Advance bushing starts to get sticky from age and deteriorated lube
(NOT rust)
2. Centrifugical force at higher RPMs exerts enough force to activate
the advance, even though it's not working freely
3. Springs are not strong enough to pull the advance back
4. Advance remains stuck at max
It doesn't take a whole lot of thinking to realize that the force of
weights trying to advance the timing, especially at higher RPMs, is
going to be much greater than the force of the return springs. If this
wasn't the case, you would not get any centrifugical advance at all.
And of course the problem isn't rust, not down in the bushings, when
the advance mechanism gets bad. It's loss of lube, or carbonized lube.
The rust on the weights and springs doesn't make a whole lot of
difference unless it's ridiculously extreme.
jim
Vic Smith wrote:
>
> Forgot that ported vacuum. My 350's were a '76 and '78.
The electronic ignition on the 350 started in 1971, IIRC. It was an
option for maybe 2 years but after that they all had it.
> Probably my '66 352 was the one with manifold vacuum.
> I think they all had the window in the cap for dwell adjustment.
> My '64 Bug didn't have a window, but I could use a continuity light
> and feeler gauge for timing and dwell.
> >
> >> If you're curious you'll check the advance with your light before you
> >> set your idle. Goose it to see the mechanical advance.
> >> Whether you check it or not, if the advance is bad, I think you'll
> >> have noticeable performance problems.
> >
> >No there are no noticeable performance issues (at least not for the
> >first 5k-10k miles). The advance works only under lighter loads. So if
> >you accelerate hard it behaves the same whether the advance is
> >functioning or not.
> >
> >
> >> Although I never had a bad one, I did always check when I did a tune
> >> up.
> >
> >So how much advance were you looking for and how did you go about
> >measuring it?
> >
>
> Don't remember how many degrees. I always had specs for all this and
> followed the book. Best I can recall is goose to maybe 3 grand on the
> tach and see maybe 30-40 on the mark.
My point was there are no such factory made markings for that much
advance. So if you had markings you would have created your own. And in
the '70s under the first generation of emission standards it wasn't easy
to find the specifications for timing. The base timing for any
particular engine was contained on the under-the-hood sticker and you
had to dig into the specifics of distributor model to find the rest of
the info.
-jim
That Tune
news:0547c64b-c8df-4147...@l2g2000prg.googlegroups.com...
Well:
****
I find it unlikely that he'll respond at all given the unworthiness
and indefensibility of his risible remarks, which are unfortunately
and in general more the rule than the exception here.
jim
Ed Treijs wrote:
>
> It appears that you did. Why are you asking about what you wrote a day
> or two earlier?
You misquoted what I said in order to give it a different meaning.
>
> > It is however extremely likely to have failed once in 35 years. That
> > probability is getting pretty close to 100%. If he still has the
> > original tires on this car it would be likely that they would have
> > failed by now, also. And any other rubber component on this car is
> > likely to fail after 35 years.
>
> The original vacuum advance canister, the heat riser vacuum motor, and
> the vacuum choke breaks on the carburetor of my '78 Pontiac all work
> fine.
So you say.
> Apparently my car is the Miracle Shrine of Lourdes. Tell you
> what, I'll check the state of the vacuum advance canisters on the old
> Chevy and Buick HEIs I have lying around at home. They're original
> from the late '70s.
Doesn't sound like you would be able to tell if they were not working as
designed.
>
> > The failure of the vacuum advance will cause the engine to deteriorate.
> > The vast majority worn out 350 engines made in the 70's wore out because
> > the vacuum advance diaphragm started to leak. The reason is simple -
> > mechanics never bothered to check the the vacuum advance and the effects
> > of a non-functioning vacuum advance doesn't show up as an immediate loss
> > of power or performance but instead take its insidious toll on an engine
> > over 10k - 20K miles or more.
>
> Please explain exactly what the effects of the failed vacuum advance
> are on 1) the engine's functioning; and 2) on the car's driveability.
> Then explain the causal mechanism by which a failed vacuum advance
> causes the engine to 'deteriorate'?
The effects are that the fuel in the cylinders is combusting much later
in the power cycle when the engine is cruising under light loads. This
will accelerate cylinder, ring and valve wear. And since the highest
combustion chamber temperature is seen when lot more of the cylinder
wall is exposed it will also coke the oil that is sitting on those
exposed cylinder walls. This means the crankcase oil also deteriorates
faster and that may lead indirectly to things like oil pump, lifter and
cam wear.
>
> > >Furthermore, if it fails, it will typically spring a
> > > leak. No vacuum advance will hardly make the cam go bad.
> >
> > How do you know the cam has gone bad?
>
> We don't. However, you jumped in by saying 1) "Get a new cam from the
> junkyard", followed by 2) "A bad vacuum advance is a horrible thing".
> I assume you were linking the bad advance to the possibly bad cam. Or
> are you just saying whatever comes in your mind, relevant or not?
You have trouble focusing on more than one issue at a time.
Lack of lube will cause a rod or main bearing to seize and that is
because the lube is there to reduce friction - the bearings will melt
without lube. But there is practically no friction involved in the
distributor advance mechanism. Remove all the lube and it isn't going to
stick by itself. It will function just fine without any lube (assuming
it doesn't rust). It certainly will not seize due to friction involved.
It will stick when the lack of lube leads to rust and that is
because the rust displaces considerably more volume than the metal it
comes from. If there is no rust the lack of lube will (in the worse case
scenario) just make the mechanism become loose and sloppy over many
miles of use. Rust is pretty much the only way the clearances can be
used up and cause it to seize. It is very unlikely to develop that rust
while the engine is running at high speed. Much more likely that rust
will develop when its left to sit.
Not that any of this matters when the base timing is set where it is
supposed to be. No matter what position it sticks in the result will be
the same.
That Tune
news:Wf2dne8saaAliDrQ...@bright.net...
An absolute, unmitigated, steaming pile of shit.
Vic Smith
wrote:
>
>My point was there are no such factory made markings for that much
>advance. So if you had markings you would have created your own. And in
>the '70s under the first generation of emission standards it wasn't easy
>to find the specifications for timing. The base timing for any
>particular engine was contained on the under-the-hood sticker and you
>had to dig into the specifics of distributor model to find the rest of
>the info.
>
Okay, I buy all that. My memory is worse than I thought.
Not the first time my memory made things up, so I'm not shocked.
But I'm sure I had no problem seeing both vacuum and mech advance on
the mark on my V-8's for whatever good that did me.
Also remember you could get a good estimate by watching it go off the
mark onto the chain cover.
So seeing the advance was working in some fashion wasn't hard to do.
I don't think dist advance is as critical or failure prone as you do.
Never knew anybody who went to the length of getting a dist tested on
a dist machine, but I was never a hotrodder.
All dists are probably off some degrees at certain ranges.
Only dist I replaced was the one on the '64 Bug.
Read the vacuum advance often failed and followed recommendations
to put on a Bosch all mechanical.
As far as specs I had Motor's manuals that covered quite a bit.
I never lacked for specs when I did engine work.
The used '76 Caprice 350 I bought had the cat pulled off and who knows
what other emissions disabled but I never had a problem tuning it to
run smooth at all speeds.
Same with the '78 in the van.
Anyway, the valve train noise the Vette guy hears has nothing to do
with the dist. Different issue entirely.
--Vic
ben91932
> 1. BUT how do I tell which is exhaust and which is the intake valve
> with the intake manifold on? Been looking in the book and I see no
> info on that.
>
E II EE II E
HTH and good luck,
Ben
BSAKing
at the beast. I pulled the valve covers and intake manifold and put a
micrometer on the push rods while hand rotating the engine. It turns
out one exhaust lobe (at least) was worn down to a nubbin. The
micrometer rotated 2 1/2 turns with other valves and barely once on
this one. Several of the lifter seats were showing signs of wear and/
or scaling. I would not be surprised if other lobes were worn to some
degree or another.
So - I ordered a cam kit (cam, springs, lifters, etc) from procams (a
little more aggressive than the stock but not wild at all) and a
complete gasket set for a rebuild. I have a chum going to lend me an
engine puller and a motor stand. I figure maybe over the next few
weeks I'll see about getting the motor out of the car for a looksee
and cam replacement.
While I was at it, I also ordered a complete new HEI system on-line
(by the time I replace the parts on the original it would be the same
or more money wise), and this way I am eliminating the shaft play on a
35+ year old unit.
I have never done anything like this whatsoever before, but it does
not appear to be rocket science, although there surely is a lot to
learn in terms of tricks and tips! And for sure I'll be asking some
questions along the way that experienced folks may roll their eyes
at.....
We'll see how it goes - either "The thrill of victory, or the agony of
defeat!" lol.
BSA
jim
BSAKing wrote:
>
> Just an update - I finally screwed up the courage to look more closely
> at the beast. I pulled the valve covers and intake manifold and put a
> micrometer on the push rods while hand rotating the engine. It turns
> out one exhaust lobe (at least) was worn down to a nubbin. The
> micrometer rotated 2 1/2 turns with other valves and barely once on
> this one.
You must mean a Dial Indicator
http://precisionindicators.com/Dial%20Indicators.html
This is a micrometer
http://www.technologystudent.com/images3/microm1.gif
-jim
BSAKing
Exactly! One of dose dere tings. Thanks for the correction! That's
exactly what it was.
I now have the A/C, alternator, distributor, intake, carb etc off and
have to disconnect the rad and get the fan shroud out of there before
pulling the engine. Should be fun! I have never done any of this
before.....
N8N
> "willy" <danceswithbe...@embarqmail.com> wrote in message
>
> news:9bd97d82-0304-4126...@u8g2000yqh.googlegroups.com...
> On Apr 8, 8:09 am, jim <"sjedgingN0Sp"@m...@mwt.net> wrote:
>
>
>
> > You may have a bad camshaft. What year is the engine?
>
> > -jim
>
> What does knowing the year of the engine have to do with diagnosing a
> bad cam?!?!
> I have a 300hp 350. It doesn't run right. It's a 1969. Can you tell me
> whats wrong with it? lol
>
> ******
> I think what he was getting to was that some years and models of
> engine have known problems with cam wear, lifter stud slippage,
> etc.
>
> The OP's symptoms COULD come from a bad cam lobe, but that
> is not the only thing that would cause his problem.
>
> At least, that was the way I interpreted his post.
Ayup. my dad had this problem on a '73 307 (truck motor) with not too
many miles on it IIRC. I was still a little kid when it had the cam
replaced. (at least I think it was the 307. Might have been the
junkyard 350 that replaced it. There's a looooong story in there that
would probably amuse the group, but I haven't time to relate it ATM.)
nate
ausk...@yahoo.com.au
Paul in Houston TX
> On Sunday, 10 April 2011 03:16:05 UTC+10, That Tune wrote:
>> "BSAKing" <bsa...@gmail.com> wrote in message
>> news:20e2f257-e881-48d6...@k11g2000yqc.googlegroups.com...
>>> Well - I have been reading the updates here.
>