Head gasket repair or crate motor

[Schurkey]

WHICH head gaskets are you going to use?

The common ones are .040 thick composition gaskets. They're a disaster. You'll destroy whatever quench/squish the engine has, which was probably pretty meager to begin with.

GM and the aftermarket sell .028 composition gaskets, they were common on '90s engines. Better. Not optimum.

Given any choice, I'd use .015 steel-shim gaskets IF (big IF) the block and head gasket surfaces are FLAT and SMOOTH. These come with a rubber-ish coating to help them seal.
https://www.summitracing.com/parts/fel-1094

Don't forget to buy some Loctite/Permatex 592 sealant for the head bolts. Use the SPECIAL TBI intake manifold gaskets if you're using the OEM TBI intake manifold.

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[thinger2]

160? Take your time, do the head gaskets right
And drive it for another ten years
Maybe more

 

[Ross Fellrath]

WHICH head gaskets are you going to use?

The common ones are .040 thick composition gaskets. They're a disaster. You'll destroy whatever quench/squish the engine has, which was probably pretty meager to begin with.

GM and the aftermarket sell .028 composition gaskets, they were common on '90s engines. Better. Not optimum.

Given any choice, I'd use .015 steel-shim gaskets IF (big IF) the block and head gasket surfaces are FLAT and SMOOTH. These come with a rubber-ish coating to help them seal.
https://www.summitracing.com/parts/fel-1094

Don't forget to buy some Loctite/Permatex 592 sealant for the head bolts. Use the SPECIAL TBI intake manifold gaskets if you're using the OEM TBI intake manifold.

You must be registered for see images attach

Alright Shurkey, thats some good advice there. How flat are we talking? can I measure this with a nice straightedge? It's milled to a .001" my buddy made it for me. Do I need to take these heads somewhere? I would use that top gasket because I have the TBI? I think I'd stick with it because it does work good. Anything else I should consider?

 

[Ross Fellrath]

Thanks for the well wishes for my girlfriend everyone, she's fine, totally asymptomatic. Also thanks for the encouragement on the head gaskets. I think my buddys gonna come help me so that's great. Anything else to watch out for when replacing them? Any good tricks to make it easier? Thanks!!!

 

[Schurkey]

How flat are we talking? can I measure this with a nice straightedge? It's milled to a .001"

Limits for flatness would be .004. If your straigntedge could be off a thou, your new limit is .003 from end-to-end. Tighter than that, crossways.

Do I need to take these heads somewhere?

Do they need valve/seat/guide work? At minimum verify that stuff, and cram in new valve stem seals.

I would use that top gasket because I have the TBI? I think I'd stick with it because it does work good.

You need that gasket set if you're using the GM TBI manifold.

Anything else I should consider?

Remove ALL TRACES of the old gasket, clean the threads of the bolts, and the bolt holes. Seal the head bolts with the 592. Torque to spec using a decent torque wrench that's still in calibration.

Common for the quick-connect supplying the heater core to corrode to dust. The Dorman replacement is (surprise!) a very fine piece.

...and I keep forgetting: VERIFY how far "down in the hole" the pistons are, at TDC. Typical is .025--.030. The .015 gasket gives a quench of .040--.045. Close to perfect.

 

[blackdeathmessenger]

I'd definitely try the head gaskets (with new bolts) first if the surfaces are still flat. If the block is flat and the cylinder heads aren't, then it might be time for better heads. Just my .02 cents worth

 

[thinger2]

Gaskets are used to compensate for and seal the differences between machined surfaces.
You will never get a head and a block flat and paralell within .003
If you did manage that, it would change when you torque it.
Heres an example
This is my latest reciept from Autozone on a calibrated micrometer.
Take out your latest reciept and figure how you are going to achieve that.
Friggen nonsense.

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[blackdeathmessenger]

Hey thanks for the advice everyone!!! I've learned a lot already! I think me and my buddy are gonna give the head gaskets a shot. What do you think, replace them with the motor in our out of the truck? I'll for sure let you know how it goes. Also sorry for not getting back right away, my girlfriend tested positive for covid, so that's kept me rather busy. We're both healthy, so I'm thankful for that!!!

I've installed heads with the block still in the truck. If you start in the morning, you should be able to get the truck running again before nightfall. I wish you both a speedy recovery

 

[thinger2]

Geez, a friend and his wife just got it too.
Ive known them for fourty years and they say it is the worst thing they have ever experianced.
350 head gaskets are easy, its a dirty nasty pain but they are easy.
Dont let people try to convince you that its nuclear reactor surgery.
It isnt,
Theyve been replaced on the side of the road and under trees and in snowstorms and every other place you can imagine.
And a lot of them have been swapped by high school kids.
A lot of them.
If you are in a big hurry, 3 hours.
If you have the time, a couple of casual weekend days including beer.
Nothing to it brother.
Hope you all get well fast.

 

[Schurkey]

Gaskets are used to compensate for and seal the differences between machined surfaces.

Yes...within reason. Steel shim gaskets are fairly sensitive to flatness/smoothness. The gaskets I suggested have a coating on them that probably helps with the "smoothness" part. The original steel shims had no coating, you'd spray 'em with aluminum paint, or coat them with any one of a dozen different gasket sealers.

You will never get a head and a block flat and paralell within .003

Easy. Have them planed. Hopefully, the block is good-to-go. Heads may need to be machined once removed. You understand that the head(s) measure within .003, and the block should be the same...but that would be .006 combined in the worst case.

If you did manage that, it would change when you torque it.

Of course. This is why the manufacturers spin all the head bolts at once during manufacture, and why the service procedure involves a specific torque pattern.

Heres an example
This is my latest reciept from Autozone on a calibrated micrometer.
Take out your latest reciept and figure how you are going to achieve that.
Friggen nonsense.

As I said, the standard for ordinary, old cast-iron automotive engines is about a thousandth per hole--a four-cylinder head is .004, a six-cylinder head allows .006. 'Course, that could change depending on the specific engine.