Head Gaskets: To Seal Or Not To Seal

[San_Diego_SeaRay]

I need to replace my head gaskets on my 1981 MCM 260 engine. Service Manual #3 on page 6C-49 says to use Perfect Seal on Stainless Steel head gaskets, but not to use anything on Composition Steel Asbestos gaskets. Well my head gasket was manufactured more than 30 years after the engine was built and I imagine well after this book was written. My gaskets feel like some kind of plastic/teflon material w. metal rings lining the inner perimeters of the holes. So what should I do? Use Perfect Seal or skip it?

Also, what's the best way to clean out the threaded holes for the head bolts?

 

[Bt Doctur]

Nothing usually goes on the head gasket, the correct size tap is used to clean all the holes in a block.When installing head bolts,wire brush them clean and coat the threads liberally with sealant not perfect seal.

 

[San_Diego_SeaRay]

Nothing usually goes on the head gasket, the correct size tap is used to clean all the holes in a block.When installing head bolts,wire brush them clean and coat the threads liberally with sealant not perfect seal.

OK great thanks. So the manual specifically says Perfect Seal on the bolt threads, but you'd suggest using something else? When you say sealant, something like 3M 5200?

 

[Fun Times]

OK great thanks. So the manual specifically says Perfect Seal on the bolt threads, but you'd suggest using something else? When you say sealant, something like 3M 5200?

You don't want to use 5200 due to it's more of a permanent sealant and not designed for this situation.

The sealants to use would be something more like the ones linked below for example,
Permatex head bolt sealant w/Teflon, http://www.permatex.com/products-2/p...sealant-detail

http://www.amazon.com/Loctite-115851.../dp/B004QXL4F2

GM part number 12346004 or 1052080 would be the OEM sealant.
http://www.gmpartsdirect.com/perform...ATID=1251.html

http://stuffspec.com/Read/c9890d17f...15546e9cae11f96b714f0efc87d128fdba2b.pdf.html

Different types of head gaskets are available. If you are using a steel/asbestos composition gasket, do not use gasket sealer.

Sealant Notice
Notice
Do not allow RTV sealant to enter any blind threaded hole. RTV sealant that is allowed to enter a blind threaded hole can cause hydraulic lock of the fastener when the fastener is tightened. Hydraulic lock of a fastener can lead to damage to the fastener and/or the components. Hydraulic lock of a fastener can also prevent the proper clamping loads to be obtained when the fastener is tightened. Improper clamping loads can prevent proper sealing of the components allowing leakage to occur. Preventing proper fastener tightening can allow the components to loosen or separate leading to extensive engine damage.

 

[alldodge]

Clean thread holes out with plumbers wire brush

In the old days they specified oil or grease. Then they went to antisieze. I use ARP sealant which is antisieze and grease kind of mix. Pulled a Merc reman apart and found something which looked like sort of silicone. Called Merc and they said it was Permatex

 

[San_Diego_SeaRay]

OK great thanks guys. I think I'm set for this weekend!