Re: Headgaskets

Posted by Joe on March 16, 1998 at 07:58:20

In Reply to: Timing Cover Rope Seal Revisited; Head and Pan Gasket Sealants
posted by Gordon Biggar on March 15, 1998 at 18:45:24

Gordon
I'm glad you got past your front seal problems.Sometimes improvisation (and a little knowledge) is the best way to get past a problem.
I have seen many different methods of applying the headgaskets advocated on this board.Likely you will get *many* different answers from respondants.
I feel the best advice to making the headgasket work is to have the head and top of the block reasonably flat (certainly within .005).Some on this board have advocated a rough "as machined" surface.A tough thing to specify or measure but this only makes sense if you're fortunate enough to have it.
I always use a standard copper headgasket and have applied it both with and without the red spray permatex adhesive.Now that I have seen it done both ways, I think I prefer to put the gasket in without the adhesive if I can (I don't like that unsightly red line and bubbles that form at the gasket edge) but if the gasket has blown or I am afraid it might, I give the adhesive a try.
On assembly I torque everything up to 50 ft-lbs or a little beyond.Then I walk away for a day or two and give everything time to relax a little.Then torque everything up again.Then start the engine and let it get hot.Then torque it up again.Then do the cooling-heating cycle once again and torque it a last time while hot.Then about a month later after several heating-cooling cycles, top off the torque once more.Needless to say, don't torque while the engine is running.
You will want to lubricate your nuts and their studs prior(this makes a dramatic difference in the amount of torque being translated into tension, which is really what you want) and I typically use plain 30W oil on the head nuts although on other machinery that I work on where appearence is not an issue I use Never-Seize.Never-Seize is a more effective lubricant for this purpose and now washes off with soap and water if you want to go through the extra step.
If you break a stud in this process, it just indicates a weak stud which should have been replaced anyway.You'll really love getting the broken stud out of the hole.I have been known to "recycle" studs although on really serious work I prefer to replace them with new.An engineering rule of thumb is that if a stud will survive torquing, then it will survive the remainder of it's service life without failure.
I also typically use "teflon tape" on the bottom (block) end of the studs just to seal the penetrations into the water passages of the engine.It's kind of slippery and makes removal of the studs easier later on also.There are those that may cringe at this method feeling that in the process of torquing the stud will wind it's way into the block and split out the threaded hole to the side - but that's the natural tendency of the studs anyway and splitting out has never happened to me.The difference in the thread pitch between upper and lower end of the stud probably accounts for the reason it doesn't.I'd rather have the sealant in place and take the chance.
I have had a head up to .015 out of flat and been able to get it to seat, although it is a little chancy at this amount.This particular engine did develop a headgasket leak midway through my normal routine (milky oilpan, etc.) but by tearing everything down and starting new, using the red stuff, and this time making sure everything was torqued up to the hilt and checking torque several times, I was able to get everything to stay seated and in place.It's kind of amazing how flexible everything is.
Hope this all helps.Let us know how you make out.
Best regards,
Joe

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