Hi everyone,
I've decided to change out my head gaskets. The manuals say to use "sealant" on the bolt threads. They don't say what type of sealant: Permatex Blue RTV silicone gasket maker? Permatex 2B non-hardening sealant? I've also been told by one guy to use Teflon goo (as opposed to teflon tape). Any suggestions?

On reading my Permatex Blue RTV tube it says not for parts continuously immersed in gasoline. For future reference, if a sealant cannot withstand gasoline, should you assume it also cannot handle engine oil?

As I have not pulled the heads yet, where do the bolts go? Are they into oil or into water jacket?

Last Q: I'll be replacing the intake manifold gaskets, too. One book says to use silicone sealer. I suppose the Permatex RTV Blue silicone sealer is what they have in mind? Something better?

Thanks! Patricia/'75 Corvette

Silicone or teflon paste either one will work fine to seal the head bolts. Telfon tape adds a more solid bulk to the threads, and may throw off the torque readings, leading to less clamping force and gasket failure. I recommend against Permatex 2. It will work fine, but is harder to take apart later if the need arises. Permatex 1 is almost impossible.

Some of the head bolts go into the water jacket, some go into blind holes (they don't go anywhere). Oil is a factor in some cases, but GM recommended silicone to seal the oil exposed head bolts on the 2.5 engine. So no problem. It's not a good idea to use it in a carburator or fuel supply. While oil can be distructive to seals, gas is more of a solvent then oil, even long term.

Be sure the blind holes are cleaned before you put the bolts in. If you seal the oil/water in the bottom of the hole, tightening the bolt can cause pressure in the hole as the bolt goes in. The very high pressure can cause metal cracking. If the bolt is tightened very slowly, the fluid will often come up past the threads. Don't count on this when the bolt has sealer (or even if it dosen't). If you trap fluid, the heat related expansion can later cause cracking. Blind holes do not need sealer of any kind, but it won't hurt either.

The manifold does use silicone to seal. Don't put it on too thick, or when it squishes out it can get where you don't want it to go. It can block intake and water passages, or get inside the engine. Of course too thin may not seal. It needs to be thicker on the ends than on the side gaskets.

In both cases I prefer the blue silicone, but black or orange will do just fine. Copper is for higher heat areas.

Ken Styer

|UPDATED|2/23/2004 8:55:03 AM (AZT)|/UPDATED|

Thanks, Ken. I'm glad you mentioned to watch for water getting trapped in the bolt holes. I can see where that could be a real issue. I'll put the ShopVac to use on those blind holes to be certain everything's clean.

An air blow gun also works well. Just watch your eyes.

Ken Styer

The best thing i've found is gm part#12346004 sealant. I had some problems in the past with oil coming up around the center bolts on the intake.On the last two motors I used this, and no problems