hello, and greetings from austria again!

does anybody know which thickness the original 3A head gaskets from 1977 had?

i ask, because i rebuilt my engine with a comp cams 260h and flat top pistons 0.030. also grinded down the air bumps and ported a litte bit.(--> home porting is not a crime ) and that stuff. project is still in progress.

the 260h ,,likes,, a compression ratio of 8,5-9:1.

i have the blue fel pro gaskets, and a pair of rocket racing 0,028''.

i dont want to get too much compression now with the shim gaskets, but if GM used shim gaskets 1977 it would be the compression now i need.

thanks for input, simon.

 

The 77-80 use different head gaskets, don't they? They are listed as different.

 

I think that year range used the thicker (.040") composition head gaskets.

 

If you did some porting, did you measure the volumes of your combustion chambers?

If not, you should. Then you can calculate your compression ratios properly and be certain.

- Eric

 

77-80 are different shapes. You're kind of stuck with what you get at the box stores. Or order custom.

If you put a 77-80 gasket on a 65-76 block , It will leak as soon as you pour the water in the engine.


I have never tried 65-76gaskets on a 77-80 engine, but I imagine the results will most likely be equally disappointing

 

thanks for answers, but i know that the 77-80 gaskets are different. i have the correct fel pro gasket kit for that year. the question is, if they where thinner in the year 1977 for THAT engine than you can buy them now?! because many earlier olds engines used to be 0,025 or so.

 

not yet. would it be possible to give me a link how to do exactly?

 

You will have 9 to 1 compression, just run the Fel Pro's. I believe those years ran the .040" head gaskets factory.

 

I don't have any links, personally, but I can tell you what I do (which is not the same thing that everyone else does):


I have a piece of broken glass from a basement window that I use for cc'ing. It has an inwardly-curving edge, which makes it excellent for the purpose.

First, I make sure that the head is essentially level, perhaps tilted the tiniest bit away from my position, so that the open area under the glass fills last (rather than having an air bubble form at the far end).

I clean the sealing surface of the head thoroughly with an appropriate abrasive (ScotchBrite pad or ScotchLok wheel) to remove any corrosion or bits of sealing material, then I coat the sealing surface with a thin layer of Vaseline (any thin grease is fine, but Vaseline is very easy to clean up).
I then firmly press the glass down against the Vaseline, making sure to press any air out. If there are areas that aren't covered well, I remove the glass and add a bit more Vaseline.

Once the glass is in place, I use a 20cc syringe to slowly fill the combustion chamber with denatured alcohol (ethanol or methanol). Keep filling (and counting) until the small area that is not covered by the glass is perfectly level with the sealing surface of the head (look at it from the side).
At that point, add up the number of ccs of fluid you added to get the volume of the combustion chamber.

The alcohol can be sucked out with the syringe and used again in the next cylinder.





That's pretty much all there is to it.

- Eric

 

I do the same thing, but with a smaller piece of plexiglass with a tiny hole drilled near the edge for fluid insertion/removal.

 

Yeah, finding a piece of broken glass in the basement that happened to be about the right size saved me the trouble of finding, cutting, and drilling the plexi - and I know it's flat.

- Eric

 

thanks, eric