type 1 valve clearance issue
Tom Jordan
With a stock type 1 motor, will the valve lash increase or decrease as
the engine heats up?
I ask because on my motor, I installed new factory heads, and after the
install, as the engine warmed up, I began to notice excessively louder
valve train noise (as compared to when the old heads were installed).
The valves were adjusted cold at 0.006". I drove the car a few miles
and rechecked said valves (cold). After I put about 100 miles on the
car, I re-checked the valve lash with the engine warm. I was able to
squeeze 0.017" worth of feeler gages between the rocker and stem!
The motor was a rebuilt deal that came with the car. One of the old
heads was cracked, so I replaced both. I reused the rockers and push
rods.
In case I am missing something more obvious, the motor is configured as
follows:
-1600 cc
-stock cam
-stock intake and 34 carb (rejetted for exhaust)
-bugpack hide away exhaust with heaterboxes
-new 36mm/32mm Brazilian heads
-stock single vacuum distributor with Pertronix ingitor, coil and wires
-initial timing set at 7.5 BTDC
-stock air filter
-all stock cooling tin, vanes, gaskets and t-stat in place
-mobil 1 oil
Thanks in advance for any help,
Tom
Veeduber
VW engine follows this rule.
Ideal valve lash is zero, achieveable only hydraulic tappets.
With solids, the cold lash setting of .006 is a compromise, intended to get you
close to zero lash when the engine heats up.
If you're seeing .017 hot after setting the thing at .006 cold then you've
either mistaken your cold reading, your adjuster screws are trashed or you're
not doing the adjustment properly -- using the wrong setting-point or failing
to maintain the setting whilst tightening the lock nut.
(I'll assume the adjuster screws AND the heads of the valve stems are not
trashed... but you should know that you need to replace the stock adjuster
screws about every five adjustments... the cambered end of the screw becomes
faceted due to wear and dishes-out the head of the valve stems, leading to
Chunkie Attacks :-)
Here's how real mechanics do it:
Set the pulley at or near TDC. Remove the valve covers. (Engine is cold; has
not been run for at least four hours.) By touch, identify any valve that is
NOT tight. Loosen the lock nuts on those valves, turn the adjuster screw until
it makes contact with the valve stem, then back it off an estimated 45
degrees... one eighth of a turn and tighten the lock nut while holding the
adjusting screw in position. (Be as precise as possible in your degree
estimate. Do just one bank at a time.)
Do the other bank. Then rotate the engine one full turn... bring the pulley
back to the same mark as before.
Now repeat the procedure. This time, all of the valves that were tight will be
loose.
Replace the valve covers.
(This procedure works -- and is the method taught at the factory school --
because of the pitch of the adjuster thread, one eighth of a turn being
approximately .006" of linear travel.)
The method described in St. Muir and other manuals is the procedure used when
ASSEMBLING an engine -- when the valves are adjusted for the first time. With
an engine that is already assembled, thanks to the characteristics of the Otto
cycle, the valve lash may be adjusted ANYTIME the cam-follower is riding on the
heel of the cam.
-Bob Hoover
Anthony
you need to adjust them with the engine dead cold. In your case,
something is probably not tight. Check all the locknuts on the valve
adjusters, and check the bolts holding the rocker assemblies to the
head. One may have loosened and caused all your valves to have way
too much clearance and make a lot of chatter.
~Anthony
Tom Jordan <te...@cornell.edu> wrote in message news:<MPG.1ba903559...@newsstand.cit.cornell.edu>...
Sleepy Joe
>
> With a stock type 1 motor, will the valve lash increase or decrease as
> the engine heats up?
>
> In case I am missing something more obvious, the motor is configured as
> follows:
>
Check in the John Muir How To Keep Your Aircooled VW Alive book and
in the Roberta Haynes repair manual that applies to your vehicle.
Wherever three or more agree right?
Lane Jennison
Check the Bob Hoover manual. It seems to be more precise.
Lane
Veeduber
Tom writes:
-------------------------------------------------
> I double checked the
>valve clearance cold several times, so I am confident we can rule out
>the a mistake with the initial adjustment (.006").
------------------------------------------------------
Dear Tom,
You've missed the point (and the reason I described the most common method of
adjusting the VW's valves).
The valves should only be adjusted when the cam-follower is riding on the heel
of the lobe. The pulley is a demountable item. Over the years it's quite
possible for the pulley from another engine to be substituted for the original.
Even if everything is all-original the marks on the pulley are only an
APPROXIMATION to be used only for IGNITION timing.
(Accuracy of the notches on the fan pulley is usually +/- 1.5 degrees, close
enough for the engine to start. Once started, the ignition timing is dialed-in
using a stroboscopic timing light.)
Another assumption embodied in your original message is that the cam is stock
and the engine has been properly assembled. The limitations of email make it
wildly impractical to try and nail down such assumptions but the described
method of valve adjustment will work in any case.
------------------------------------------------------
.
>
>The adjuster screws have a few thousand miles on them, so I guess they
>can be potnetially in need of replacement. They are somewhat faceted.
>
>I still don't see how trashed screws could create a hot clearance of
>0.017".
--------------------------------------------------
The faceting of the cambered face of the adjusting screw is just the tip of the
iceberg. Once the face is faceted any future adjustment is liable to bring the
EDGE formed by two facets into contact with the valve stem. Having a
significantly smaller area, the edge wears at an accelerated rate, often
needing only a few miles to open the adjustment beyond spec. The other part of
the problem is that the edge also greatly accelerates wear/deformation of the
head of the valve stem, making first a groove then folding the edge of the
valve stem outwards until it cracks. When the valve stem is worn in this
fashion -- even moderately -- and when the adjuster screw is faceted, it is
impossible to accurately set the valve lash using a feeler gauge, since it
simply bridges the groove in the one while touching the edge of the other. You
may think you have a nice .006 fit when in the actual dimension is much
greater.
---------------------------------------------------
<< I am confident we can rule out>>
Automotive engineering has nothing to do with your confidence (nor that of your
pet mouse :-) Having the valve lash open up when hot is the symptom of a
problem. Until the problem is defined it would be unwise to rule out anything
based on human perception.
If that sounds a bit harsh please understand it not meant as a put-down. A few
minutes poking through the archives will show you literally hundreds of
requests for help from people who have already decided what the problem can and
cannot be -- "I know it can't be that because..."
Such determinations are not up to us. The engine or the chassis or the
electrical system always has the final say. All we can do is try and interpret
the symptoms -- as colored by your perceptions.
<<They are somewhat faceted. >>
That's like saying your girl friend is slightly pregnant :-)
Faceting of the adjuster screws is normal. The service manual says to replace
them 'as required' which works out to about every fifth valve adjustment. This
chore may be eliminated by using swivel-foot adjusters, assuming the face of
the valve stems are still true. (Back in the Good Ol' Days... whenever that
was... the parts-guy kept adjusters bagged in sets of eight right there on the
counter. I can't recall the price... I think it was about a buck per set.)
-Bob Hoover
dragenwagen
belt. I may as well just do a complete tune up and oil change while I am at
it...
--
****************************************************************
dragenwagen
1966 Type I - Daily Driver
1969 Type I - Undergoing heater channel replacement
http://www.ramva.org/dragenwagen
"Old VW's Don't Leak Oil, They Mark Their Territory."
****************************************************************
"Tom Jordan" <te...@cornell.edu> wrote in message
news:MPG.1ba903559...@newsstand.cit.cornell.edu...
Jan Andersson
Tom Jordan wrote:
>
> Hi,
>
> With a stock type 1 motor, will the valve lash increase or decrease as
> the engine heats up?
8< snip >8
Considering you have so many new parts and work done on the heads, I'd
say this is normal during the first couple hundred miles. All the parts
wear in and seat themselves for a while at first, until they settle.
Keep a close eye on the valve clearance for the first 2k miles. If one
or two valves seem to *lose* clearance repeatedly, you may be looking at
a stretching valve... about to snap. Usually happens to old valves
though.
Jan
Jan Andersson
Veeduber wrote:
>
> Virtually all metals expand as they get hotter. All of the metal used in the
> VW engine follows this rule.
>
> Ideal valve lash is zero, achieveable only hydraulic tappets.
>
> With solids, the cold lash setting of .006 is a compromise, intended to get you
> close to zero lash when the engine heats up.
>
I just thought of something: If he used steerl pushrods to replace old
aluminum pushrods with (by someone's recommendation perhaps) then the
lash would get bigger as the engine heats up....
Jan
Chris Perdue
>
>I still don't see how trashed screws could create a hot clearance of
>0.017".
>
do you have "chromoly steel" pushrods? if the answer is yes, you will need to
learn to love noisey valves or switch back to alluminum pushrods...
-------------------
Chris Perdue
"Sometimes you're the windshield, sometimes you're the bug!"
Remove "PANTS" to e-mail
Veeduber
>I just thought of something: If he used steerl pushrods to replace old
>aluminum pushrods with (by someone's recommendation perhaps) then the
>lash would get bigger as the engine heats up....
----------------------------------------------
Dear Jan,
Here... put on this tall, pointed hat. Now go stand in that corner over
there... no, facing the wall.
(For your supposition to be correct the steel-tube push-rods would need a
negative co-efficient of thermal expansion. But they don't. Steel expands
when it gets hot, just like aluminum... only not so much. The hot valve lash
would still be something less than .006" rather than more.)
-Bob Hoover
-PS -- If you're running steel push-rods of stock length, start with a cold
lash of .004, check to make sure that you still have some clearance when the
engine is hot.
Longer than stock? Then try a little less. How much? You'll have to work it
out empirically. But steel push-rods, be they in a Buick or a bug, ALWAYS
expand less than aluminum push-rods in the same engine. So take it into
account. Or buy ear muffs. Your choice; you're the Mechanic in Charge.
Jan Andersson
Veeduber wrote:
>
> Jan writes:
>
> >I just thought of something: If he used steerl pushrods to replace old
> >aluminum pushrods with (by someone's recommendation perhaps) then the
> >lash would get bigger as the engine heats up....
> ----------------------------------------------
>
> Dear Jan,
>
> Here... put on this tall, pointed hat. Now go stand in that corner over
> there... no, facing the wall.
>
> (For your supposition to be correct the steel-tube push-rods would need a
> negative co-efficient of thermal expansion. But they don't. Steel expands
> when it gets hot, just like aluminum... only not so much. The hot valve lash
> would still be something less than .006" rather than more.)
>
Bob, I agree with what you said, the theory of it is correct. But at the
same time you yourself explained why the clearance GROWS. It's indeed
because of the slower/lesser expansion of steel vs. aluminum. You still
have a huge lump of an aluminum head sitting on top of the cylinder,
expanding as usual. Factory stock engines had aluminum pushrods,
carefully designed to make the valve clearance get just a tiny bit
smaller when the engine warms up. It really only takes a material change
from aluminum to steel (pushrods) to go the opposite direction, the
steel rods dont expand enough to allow the gap to get narrower, but
instead will "fall short". Then you have the head that still expands,
more than the now steel rods.. taking the rockers further away from the
rod tip. It's all very minimal, but it is noticeable to a trained eye.
Ear. Or feeler gauges (you have to be real fast if you plan to measure
HOT valve clearance though.. man what a pain). What I'm saying is that
the difference in expansion rates is enough to not only negate the
"closing" effect, but also make the clearance actually grow. I've built
countless engines with these, and it's just something one has to accept.
Or go to high $ special parts or hydraulics or... ;)
> -Bob Hoover
>
> -PS -- If you're running steel push-rods of stock length, start with a cold
> lash of .004, check to make sure that you still have some clearance when the
> engine is hot.
>
> Longer than stock? Then try a little less. How much? You'll have to work it
> out empirically. But steel push-rods, be they in a Buick or a bug, ALWAYS
> expand less than aluminum push-rods in the same engine. So take it into
> account. Or buy ear muffs. Your choice; you're the Mechanic in Charge.
Right. No argument there.
Jan
Sleepy Joe
The adjuster screws have a few thousand miles on them, so I guess
they
can be potnetially in need of replacement. They are somewhat faceted.
Worn adjuster screws will give you inaccurate readings and will cause
premature engine wear. Just replace 'em and check the valves with the
engine completely cold.
Replace the screws or get some elephant feet adjusters from
cbperformance.com or aircooled.net .
Do not use the Empi brand elephant feet adjusters. They fall apart
fairly easily. Well mine almost fell apart, but I caught it in time.
No problem with C.B.'s feet for over 10 years now.
For engine break in,
First I would take it slow.
Drive through a residential area and do plenty of stop and go driving
for at least 30 minutes at under 1500 rpm. Park it. Let it sit over
night or at least 12 to 14 hours and check the valves with the engine
completely cold.
Then change the oil.
Then drive it for a week and change the oil and check the valves with
the engine completely cold.
Then drive it for a month and change the oil and check the valves with
the engine completely cold.
After that follow the usual oil change interval, which for an
aircooled VW with no oil filter, the strainer screen does not count,
should be at least every 1000 miles, but I would recommend at least
evcery 850 miles, and check the valves with the engine completely
cold.
I just drive mine on weekends but I still change it at least every 3
months even if that is less than 400 miles. And I check the valves
with the engine completely cold about every three months if for no
other reason, just to practice doing it.
Jim Adney
>Jan writes:
>
>>I just thought of something: If he used steerl pushrods to replace old
>>aluminum pushrods with (by someone's recommendation perhaps) then the
>>lash would get bigger as the engine heats up....
>----------------------------------------------
>
>Dear Jan,
>
>Here... put on this tall, pointed hat. Now go stand in that corner over
>there... no, facing the wall.
>
>(For your supposition to be correct the steel-tube push-rods would need a
>negative co-efficient of thermal expansion. But they don't. Steel expands
>when it gets hot, just like aluminum... only not so much. The hot valve lash
>would still be something less than .006" rather than more.)
Bob, I'm going to have to stick with Jan here. With stock pushrods the
extra expansion coefficient of the Al makes up for the fact that the
oil-cooled pushrod doesn't get nearly as hot as the cylinder and the
head studs. It's just enough extra that the lash can close down close
to zero when fully warm.
With a coefficient of expansion 1/3 that of Al, the steel pushrods can
easily expand less than the cylinder and cause an actual increase in
lash, even though the pushrod still expands somewhat.
We know that all these parts don't come to equilibrium at the same
temp, don't we?
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------