Difference in compression with iron vs aluminum head gasket?

[dbtk2]

How much does it raise compression to use the iron head head gasket instead of the aluminum head gaskets on an aluminum head engine? Not planning on doing this because it doesn't seem like a good idea on a turbo car, just wondering what the difference is.

Thanks,

Shawn

[bszopi]

From Marty is a different, recent post...

It depends on how high you want to go with the compression. Using the thinner iron head Camaro 3.1 headgasket will bump the compression ratio about 1/2 point. Using the 3.1 iron head pistons will take it up to around 12:1. Note: you CANNOT use the thinner headgasket AND the 3100 pistons, as clearance is too tight.

[dbtk2]

I'm kind of looking for more exact numbers than "about 1/2 point." That could mean .2 or .8 for all I know. Does anyone know any closer numbers? It also seems to me that it would be hard to raise it a half point with just a smaller head gasket, it seems like you would need more of a difference than that, but maybe not.

Thanks,

Shawn

[RacerX11]

The numbers I have seen show the compressed thicknes of the AL head gasket at 0.060", while the FE head gasket is 0.040". I have a spreadhseet to calculate the compression ratio, and changing the gasket takes you from the stock 8.9:1 ratio up to about 9.3:1, for a change of ~0.4 (or roughly 1/2 point).

For a turbo application, you are better off keeping the stock AL head gasket, and switching to the 3100 pistons (~9.5-9.6:1). The 3100 pistons have a taller compression height, which results in more quench area in the combustion chamber, which is good for a boosted engine.

Marty

[dbtk2]

Thank you.

As I said before, I don't plan on raising the compression on my engine, so it doesn't matter, I was just wondering what the difference was for other reasons.

Thanks again,

Shawn

[ProjectMM]

what type of engin has the thinner type of head gasket

I'm just wondering if you can use that gasket on a 3100 or 3400? just looking into future mods?

[SappySE107]

"Note: you CANNOT use the thinner headgasket AND the 3100 pistons, as clearance is too tight."

[dbtk2]

Also, I was just thinking. With the smaller head gaskets, wouldn't you need shorter pushrods as well? If so, would the difference in length be the same as the difference in gasket width?

Shawn

[sharkey]

the differance is minimal when it comes to pushrod leanth. changes like this is why you set the valves, not just throw them on.

[ProjectMM]

can you use this on a 3400 motor? if so what year motor do the they come on?

[dbtk2]

I'm pretty sure if it won't work on a 3100 that it won't work on a 3400. I think this is just for the Gen II bottom end engines.

And I'm not sure about the year, so I'm probably wrong about this, so feel free to verify or correct me on this if you know, but I think if you used them off of like a '87 S-10 with a 2.8L, you would be fine. Probably a 2.8L fiero as well.

Shawn

[RacerX11]

The 3100 and 3400 are supposed to have the same piston compression height, which means it will not work.

The gaskets to use are any 2.8 or 3.1 Camaro, or 2.8 S-10. Or any other iron head 2.8/3.1 engine. The Felpro part number for the gasket is 8699. They also offer a high performance version, part number 1029, for the S-10's, but I have no experience with it.

Marty