The GMC CCKW

Hi all.

I need to replace the inlet and exhaust outlet gaskets.

Not having ever done one before, is there anything I need to be aware of?

Are there any tips

Cheers.

Jack.

If you are talking abou the intake and exhaust manifold gaskets, the following applies:

1. Try to find old asbestos gaskets. They seem to work better than the new non-asbestos ones.

2. If the exhaust has been leaking at the head or between the manifolds, you may have trouble making it seal right again or for a long period of time.

3. You really need to seperate the manifolds to do it right which means you need that gasket too between them.

4. Set the carb heater diverter plate to the summer position as Joel suggests.

5. You must use the intake manifold rings.

6. If the ex manifold has curled up an you can no longer insert the end bolts, you need a new ex manifold.

7. Above all, read the manual on this.


As an aside, I have tried using woodstove/furnace sement on the ex ports on both sides of the gastets and 'seem' to be having good results.


Steve AKA Dr Deuce

Thanks Steve.


.......I am going in!

I have got a manual yet as there are out of stock for a couple more weeks, so is it wise to undo the down pipe joint first?

Remove the carburetor, and the Exhaust pipe, discnnrct the ventilation lines, and the Vacuum line to the brakes, remove the assembly and take it to a machine shop to check that the mating surface with the head are all in same plane. It may have to be ground so that it will have equal contact with the gasket. make sure the 3 pilot rings are present, sometimes they are omitted, and that is a no no.
Joel

Be prepared tp use some real elbow grease and be aware of the possibility of skinned knuckles.

I can help with Pilots and bent clamps, new studs, nuts etc. Airmail takes two days, and is reasonable. It is not hard, just takes time.
Joel

Remember to use Anti-Seize compound on the bolts when reassembling. If you keep the truck, you will be doing this again....

I replace the exhaust flange bolts with stainless steel bolts, nuts and washers to slow down the process of them becoming one with the manifold! I also use SS hardware on the intermanifold connection.

Oh BTW make sure you have the exhaust flange gasket and a new metal plate. As I recall, the gaskets are the same as an M35 diesel ex pipe connector gasket.

You might need a carb to manifold/govenor gasket too.

You can usually just unbolt the carb and set it on the valve cover by disconnecting the linkage and fuel line. Choke cable will move with it.

Steve AKA Dr Deuce

Besides laying a straight edge across all the ex ports to see if any come up short due to warping or erosion, check each ex port with a straight edge and look for areas where the ex had been leaking. It will errode both the manifold AND the side of the head!


Steve AKA Dr Deuce

Idon't know of any Multifuel Ex Pipe Flange Gaskets that fit, but there are plenty of asbestos GM Gaskets around, I must have hundreds..
Joel

I have bought them from VT comm salvage among others and used them


Steve AKA Dr Deuce

What's wrong with originals? They are made for the truck, have proper holes and such. They match up better with the GM-2025630 Exhaust flange seal, that triangular piece of sheetmetal that mates to the flange gasket at the pipe. Memphis has em, me too.
Joel

Nothing wrong with original. No one had them when I was lookign years ago. Memphis supposedly sold most of their stuff a few years ago.

Do you have the metal flange too?

Not a bad idea to have a 2nd source.

Steve AKA Dr Deuce

I keep the metal seals here as a convenience, as I pay more for them than most perceive their value to be. GM had them up to 10 years ago, but the number is no longer serviced. They stopped about the time the NOS Exhaust Manifold supply did. There will always be a need for these gaskets, and I even have WWII sets that I salvage from Valve grind sets.
Joel

Thanks guys,

It is now off and in the boot of my car waiting to go of to be ground. It was all pretty painless, the biggest pain in the backside was of course the downpipe nuts and bolts but did manage to keep all of my knuckles

It looks pretty tired in places and one of the ports has a hair line crack in it.

Cheers.

Jack

Hi Jack
Before you reassemble it remove and dismantle the valve in the breather pipe, inside you willfind a ball and spring, this needs to be cleaned on a fairly regular basis as it blocks and then creates pressure in the engine which in turn causes oil seals to blow.When reassembling use PTFE tape on joints where appropriate.


Cheers
Degsy