yes another stupid ?

[gnxis]

a mechanic told me you could run 2 head gaskets to increase the size of the combustion chamber.
this sounds kinda fesible but i've never heard of it before.
any help

 

[Steve Wood]

well, if they are shims, you can. And the hot airs came with two.

But assuming it is not supposed to have more than one, why would you want to?

 

[gnxis]

just curious as to weather or not it would be less prone to blow head gasket. ive done it once and if i have to do it again i want it to be the last time.

 

[Steve Wood]

I would say more prone...blowing headgaskets is usually a result of too much boost for whatever timing chip you are running. I run 9-1 compression and have not blown a head gasket.

Now, if the heads are not true to the block or the bolts not torqued correctly, you can blow headgaskets no matter what.

 

[UNGN]

Originally posted by Steve Wood
well, if they are shims, you can. And the hot airs came with two.

Did hot airs come with two? Not being a hot air guy, I have know idea, but I thought the deck height was different so they only came with one steel shim. It's us intercooled guys that use 2, isn't it?

 

[John Larkin]

What about this? If you are going with ported heads, using some math (from the cobwebbed archives of my mind) might get you the same results from the port job. Calculating the volume of the headgasket would be A = (pi) ¶r2 (r squared), so A = (3.14 * 1.9 *1.9) or 11.33 sq in based on a 3.80 inch bore. Thickness of a shim is about .018 in, so volume of a shim would be V = A * H (11.33 * .018) or .204 cubic inches. Converting that to cubic centimeters would be .204 * 16.387 = 3.34 cc. That is how much (if my math is right) that would need to come out of your combustion chamber during the porting process to equal another shim's volume. Lee Thompson said that the stock cylinder head volume is 48cc. So you'd be looking at adding 7% roughly to the combustion chamber. Could this be done with porting? I don't know if there's enough meat in there to do that, maybe. If you go with bigger valves, it'd definitely decrease the chamber size, the opposite of your goal. Oh well, food for thought...

 

[Steve Wood]

You may be right, UNGN....but a lot of us intercooled guys only run one for the compression.

I think you are right, come to think of it....normal ic cars run a composition gasket so it would take two shims to come close to that thickness...sorry, obviously I don't know anything about hot air cars either!~