[GMCnet] Rear Main Seal Replacement... Now what?

[jronguitar--- via Gmclist]

Hope everybody is having the best Labor Day. It's a little wet down here in FLA!

So, I'm taking my 95k mile 455 out of my Birchaven for a very leaky rear main seal replacement. Not planning on rebuilding but would like to replace
everything I can while it's out. Here's where I could use some much needed advise.

What would you replace while it's on the stand? Bigger oil pump? Paint it lime green with flowers? Do you have a specific part that is a "Must Have?"
What brands? Full gasket kit? I'm not the sharpest tool but I am one! :)

I did a compression test and here's the results...
1. 170, 2. 155, 3. 165, 4. 175, 5. 175, 6. 170, 7. 165, 8. 160 (seemed strange that 2 was not above 160, don't ya think?)

Looking forward to your input.

JR
--
JR Williams
St Petersburg FL
77 Birchaven

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[Larry Davick via Gmclist]

Timing chain?
--
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy

[jronguitar--- via Gmclist]

YES! What timing chain would you recommend? Double roller?

--
JR Williams
St Petersburg FL
77 Birchaven

[jronguitar--- via Gmclist]

Does a full gasket kit come with everything I would need?

[tonka6cuda6--- via Gmclist]

If its gonna be out....i would regasket the whole thing. Pull the heads, manifold etc down to the short block just to have a peak-a-boo at the valves
etc but thats only because i can do it myself.

Chances are, if the rear main is worn out the front main is not far behind.....and if you pulling the timing cover you may as well replace the chain
and gears....in order to get the timing cover off/on you might need to remove ????......you see where im going with this right....lol.

I dont think i"d rebuild it unless the cylinder boars show heavy ridging but everyone is different so YMMV.

Or slam a rear main in it....jamb it back in and deal with the rest as it comes up because all that can be done with the motor in the coach....
--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[Charles Boyd via Gmclist]

Depends on which kit. Matt would be whom I woudst asketh. I would recommend using a Ford 460 rear main seal in an exotic rubber type ( help Matt!)
instead of the OEM rope style seal. I would probably would pull and inspect everstuff. A good running engine is the best candidate for a soft
rebuild. Rings, mains, inserts, timing chain &gears, oil pump. Get the heads checked & freshened up. Cam and lifters. Always use quality parts.



JR Williams wrote on Mon, 02 September 2019 15:35

> Does a full gasket kit come with everything I would need?


--

C. Boyd
76 Crestmont
East Tennessee

[James Hupy via Gmclist]

If your 455 is stock, it has a rope rear seal. If you have the engine out
and on a rotisserie engine stand, turn it pan side up. Put something on the
floor under it, because you are going to get a bunch of coolant from the
block and heads that didn't drain out when you took the hoses off. Probably
a bunch of oil, too. If you are not going for a complete disassemble of the
engine, clean the outside of the block and pan BEFORE you go any further.
Once your significant other says it is clean, take the pan bolts out, and
remove the pan. If it is your intention to only replace the rear seal, two
ways to go here. Replace it with a two piece neoprene seal from a 460 big
block Ford engine, or use a new rope seal.
Both will require removing the oil pump and rear main cap. Inspect both
ends of the oil pump drive shaft. Any question about its condition, replace
it. There are special tools available to replace the rope seal. They come
with instructions. Read and understand them, and follow them precisely. If
you don't, you are going to be pulling that engine again, real soon. If
your rear main bearing is in good shape, leave it alone, along with the
rest of them.
Replace the front timing cover and timing chain and sprocket set. If
you suspect any bad bearings or cylinder bores, look them over carefully
from the bottom, any scoring, rebuild time. No exceptions.
Jim Hupy
Salem, Oregon

[James Hupy via Gmclist]

Don't SLAM ANY NEW PARTS into it. Just my opinion.
Jim Hupy

[tonka6cuda6--- via Gmclist]

James Hupy wrote on Mon, 02 September 2019 16:44

> Don't SLAM ANY NEW PARTS into it. Just my opinion.
> Jim Hupy
>

Hahaha....but Jim is correct....im in a unique spot with being able to do it all myself...... i would do it all when its out...its just much simpler
and makes it so much easier.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[Matt Colie via Gmclist]

JR Williams wrote on Mon, 02 September 2019 14:51

> Hope everybody is having the best Labor Day. It's a little wet down here in FLA!
>
> So, I'm taking my 95k mile 455 out of my Birchaven for a very leaky rear main seal replacement. Not planning on rebuilding but would like to
> replace everything I can while it's out. Here's where I could use some much needed advise.
>
> What would you replace while it's on the stand? Bigger oil pump? Paint it lime green with flowers? Do you have a specific part that is a "Must
> Have?" What brands? Full gasket kit? I'm not the sharpest tool but I am one! :)
>
> I did a compression test and here's the results...
> 1. 170, 2. 155, 3. 165, 4. 175, 5. 175, 6. 170, 7. 165, 8. 160 (seemed strange that 2 was not above 160, don't ya think?)
>
> Looking forward to your input.
>
> JR

OK JR, Hang on because here we go.....

A basic gasket kit MAY have everything you want, and may have some other stuff to toss. You should still plan on buy some that I will go into. Order
it early. Fel-Pro are still good, but catalogs are out of date.

Get the engine on a truly heavy duty stand. Mine toppled over once because the "heavy duty" stand failed, the replacement stand was not much better,
but I managed to not knock it over. It is a very heavy engine. I bought a very substantial third stand. As my engine was #23 for me and I don't
count engines I can lift alone, I have some habits you don't need to copy.

The low number from #2 would be a concern. I hope it may just be valves. You won't know that until the head is off.

Before you lift the heads, roll the engine over and remove the pan. Now you can open the oil pump. Look for damage and if you see none, close it
up.

As to parts, use the 460 Ford rear seal works great and is way easier to put in than the rope that was leaking. I do not know if you can slide it in,
you may have to lift the crank. If your head isn't leaking, you will want to pull #2 piston and inspect it. Lets hope the head leaks.

Even if you don't have to lift the crank, it is a good idea to uncap the center main and look at it. That is the trust bearing and most likely to be
damaged. If there is no copper showing, screw it back down. Doing the same for the rod bearings is also not stupid. Just do pay close attention
and get the caps back the way they came off and when done, do a check torque on all of them.

Now roll it back up and pull the intake and heads. The lash adjusters are now unrestrained. They need to stay where they are so you can't roll the
engine again until the valve gear is reassembled. That is pretty much true of everything. If you move it, it may not fit right in the new place.

For inspection, lay the heads upside down with the plugs in and fill the combustion chambers with gasoline. If you smoke, go out side. That gas
should sit there a real long time. If it runs out of #2, you need a valve job. Find a shop that does cylinder heads and get them to look at it.
They will have to break it down and clean it. They will show you what is wrong and may suggest that you have the guides relined. You might as well
plan to buy new springs.

While the head is off, evaluate the top ring travel ridge. If you have access to an ID mic(rometer), measure it. My engine was about that age and
the step was less than (0.00)1 for most. You will be able to feel it with a finger tip, but that does not make it bad. If it has not been using a
lot of oil, you might just leave the pistons alone. (I could not, #7 shed 120° of the rings. So, at least that piston needed to be replaced.) As
said, if lube oil consumption was not an issue then there is no reason to mess with them. That will save you a whole of money and time.

If you liked the performance, leave the cam and lash adjusters (lifters) in place. While you are there, take out a lash adjuster and clean off
something very flat - the ground table of your saw. The face of the lash adjuster should be convex. If you put it on the table and it doesn't
wobble, you might want new. If you go to put in a new cam, you will want new lifters too.

In the manual is a very clear description of how to inspect the cam chain. If it has not been replaced, at 95K it is probably bad. I put a
Morse/Quiet/Hyvo replacement chain and why is a long story. If you do get a Cloyes double roller, they can be install at 3 different timings that are
4° degrees different, be sure you pick the one you want. I degree in every cam I install (its one of those habits), but you probably don't need
to.

While you have that open, inspect the seal surface on the damper. Some kits come with a Speedi-sleave to repair this surface. If you don't need it,
try to buy a kit without it.

Order up the intake gasket with the stainless block off plates and an electric choke heater. Also find the pan gasket that has the rubber rails.
That may be what is in the Fel-Pro kit. I though I could find the single piece molded rubber pan gasket, but I never did.

There are two good oil pumps, both are Melling. There is a standard and a high volume. If you are not going to replace the bearing shells, the high
volume is advised because you will be able to use to additional flow through the looser parts for additional internal cooling.

This is getting late on Labor Day and I will have to break off about here. I will re-read this tomorrow and probably add some. If you have
questions, I will do my best to answer them and explain the answer if it is required.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

[roy keen via Gmclist]

If you use the 460 ford seal make sure the crank knurling won't tear it up. I would look close at 7&8 rod bearings . I would use the diesel pan
gaskets and get high temperature front and rear seals.
--
Roy Keen
Minden,NV
76 X Glenbrook

[jronguitar--- via Gmclist]

Matt, thanks so much, so helpful.

I'm hoping that all is well in there. I've got a ton of parts rolling in every day and am planning on ripping it out next week.

I'll know more then and will post pics.

The damn thing runs so good, I've got my fingers crossed.

JR Williams

[Larry via Gmclist]

In addition to what has been posted, here's a couple more things to consider. No need to build an oil burner. IMO....yes...IMO, Anything more than 1
qt in 3K miles (a quart between changes) is unacceptable for a new rebuild. To control oil consumption there are a several things you can do. First,
if you have new pistons as a result of boring, or are doing new rings on old pistons with a fresh hone, place rings on the pistons using this
procedure:
http://www.gmcmhphotos.com/photos/g4104-putting-rings-on-pistons.html
This will assist in limiting oil passing the rings and keep the PCV system from sucking oil into the combustion chamber. Personally, I used a gapless
ring from "Total Seal".
http://www.totalseal.com/rings-gapless-rings.html

When you do the heads, the intake valve guides are on the intake side and will have vacuum in them making them prone to oil consumption. So, the
clearances in the guides should be tight to the factory specs. Then, install PC (positive type) seals on the intakes to control oil that may go down
the intake guides. But, I would install umbrellas on the exhaust side. It is under exhaust pressure and because of the stress of pushing a 12K lb
motorhome around may run hotter than if it were in an automobile. That little extra oil that may slip by the umbrellas, will keep the guides from
scoring and seizing.

IMO there is no need to install stiffer valve springs. That engine will rarely see over 4000-4500 RPM.

Get your PCV system under control. That upper end valve train is lashing around up there putting a lot of oil misting into the air under the valve
cover. DO NOT use aftermarket valve covers that do not have baffles. The baffles are there to control the amount of oil that could potentially get
sucked into the intake manifold.

For me, I broke in my engine with 10W40 Valvoline Maxlife synthetic blend. IMO, break-in oils are formulated to allow some wear so that everything
"wears-in". Why would you want wear to take place on a new engine? All that really needs to happen during break-in is to knock the tops off of the
honing scratches in the cylinders. IMO, that happens in the first couple of thousand miles.
Doing these things has given me an engine (500 Cadillac) that consumed 1/2pint over a 4500 mile trip last winter.

So, this is just my relatively informed, off the cuff, back yard mechanic, gut level, eyeball it up and guestimate, way of doing things....that's
all...

--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

[Johnny Bridges via Gmclist]

If you're taking the engine out, plenty of advice above. For those who find a marginal cylinder like this on compression check, try 'staking' the
valves in that cylinder as we used to do on flat motors. Take off the valve cover. Loosen the rocker arms and lift them off. Take a soft face
hammer, and whack the hell out of each valve. If the problem is a bit of carbon under a valve seat this will move it out of the way. Works about one
time in four but its so simple it's worth a try befor further disassembly.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Charles Boyd via Gmclist]

Johnny, In the old days we use to drip water in the carb running at fast idle to clean carbon from combustion chamber and valves. Now GM has Top
Engine Cleaner which works but destroys a set of spark plugs. We used transmission fluid for sticky lifters and riding neighborhood of moskitos.


Johnny Bridges wrote on Tue, 10 September 2019 09:23

> If you're taking the engine out, plenty of advice above. For those who find a marginal cylinder like this on compression check, try 'staking' the
> valves in that cylinder as we used to do on flat motors. Take off the valve cover. Loosen the rocker arms and lift them off. Take a soft face
> hammer, and whack the hell out of each valve. If the problem is a bit of carbon under a valve seat this will move it out of the way. Works about
> one time in four but its so simple it's worth a try befor further disassembly.
>
> --johnny


--

C. Boyd
76 Crestmont
East Tennessee

[James Hupy via Gmclist]

Ah yes, backyard bandaid tech 101! I love it. You forgot Marvel Mystery
Oil. And STP, and etc.
Jim Hupy
Salem, Oregon

[Charles Boyd via Gmclist]

Yes sir.. parts stores had all kinds of fancy stuff if you could afford it..






James Hupy wrote on Tue, 10 September 2019 10:45

[Johnny Bridges via Gmclist]

JimH, Marvel was accepted by the FAA, we use it to lube engines during rebuild. If you stake the valve and it then shows decent compression, you
removed whatever was keeping it off the seat, and the engine would normally run on for hundreds of hours without problems. If it didn't help, the jug
gonna have to come off and the problem corrected. Nothing magic or blackhearted about it.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[James Hupy via Gmclist]

Johnny, I hope you did not interpret my posting to be critical of "Backyard
Engineering" Quite the opposite. I used your technique in the past when
applicable. Jus' a pleasant trip through memory lane. High tech engines,
heavy valve springs have eliminated the need for such techniques, today.
Jim Hupy
Salem, Oregon

[Johnny Bridges via Gmclist]

True dat. But a Continental O-200 or a Lycoming o-360 is about as far fromhigh tech as you can get:) There ain't any magic at all in the older
aviation engines, basically they're four lawnmower moters strung on one crankshaft. If the fancy quits in my Kia, I can coast to the side of the road
and get out and see what's the matter. If the motor in the airplane quits, that optiojn ain't available :)
Some of the newer stuff has become a bit more sophisticated, including the Diesels. Porsche built a beautiful aviation engine but no one besides
Mooney would fit it, so they discontinued and replaced all of them. There's a story of one of the FAA gerbils discussing the design with a German
design engineer. The FAAer said 'we want to make sure you know how to build a good flat motor' to which the Deutcher indignantly replied 'Ve built
more opposed motors last year than Avco and Teledyne haf built in total!' I suspect he was right.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Carl Stouffer via Gmclist]

My opinion:

I would rebuild the engine if I had gone to all the trouble of pulling it out and reinstalling it.

At 95K miles, the engine could last another 30 - 40,000 miles, or it could blow up on your next trip.

When my odometer turned over 100,000 miles and I had the beginnings of a burned valve, a wise friend (Steve Ferguson) recommended that I pull the
engine and transmission and completely renew them. I did not take that advice and just put newly rebuilt heads on it. Less than 2000 miles later, I
lost high gear in the transmission and subsequently spun a rod bearing in the engine. It was a LOT of work and there was an on the road breakdown and
a tow involved.

I think I would at LEAST put in new rings and bearings, an oil pump, and a timing chain and gears. My transmission gave me no indication that it was
about to fail, and I changed the fluid in it every 12K miles since I have owned the coach. I really recommend having the transmission gone through at
this point as well.

A major breakdown is inevitable in an original coach. You can choose to have it break down on the road somewhere, or preemptively take care of the
problem at home before that happens.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

[Hal StClair via Gmclist]

Johnny, best be sure your piston ain't at top dead center when you go banging on the valve stems. Bending a valve will make it a must do job of
pulling the heads.
As for 'dribbling' a little water down the carb-we used to dump a BUNCH with the motor really buzzing. You could kill a bunch of skitters doing that.
I once bought a class c with a rod knock for a song-cleaned right up after running the garden hose through it a while.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM

[Johnny Bridges via Gmclist]

Flat motors are checked as leakdown holding the prop: 75/80, 72/80, 74/80, 50/80. That last one wants staking after a 180 turn of the prop. retest
76/80 it's ok. Retest 50/80 it ain't, and at that point you normally pull all 4 or 6 off, rebuild, rering and go again. If one is truly down the
others ain't far behind. You can listen to determine valves or rings, but it's gotta come off either way.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell