thicker headgasket

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10-02-2009, 12:54 PM

#21

94blackmx5

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Quote:

Originally Posted by neogenesis2004

A thicker HG does lower your compression regardless of application. The issue is in the quench area of the combustion chamber and piston. At TDC the outside edge, exhaust and intake sides, of the CC and piston have a near contact area that pushed the combustion into the middle of the CC causing it to tumble. This reduces risk of detonation and improves combustion efficiency. When you install a thicker HG you eliminate this effect, reducing combustion efficiency.

On the flip side, because it lowers your effective CR you are able to run more boost which can make up for that loss in combustion efficiency. I think that 2 engines with the same CR, one with a thicker HG and one with dished pistons, the one with the dished pistons will be able to either run more boost before detonation or make more power at the same boost. I have no empirical data to back up this view point however.

That said, a quick and easy way to reduce CR and run more boost is a thicker HG. A more ideal way however is installing dished pistons. In direct application to our motors, you can make enough power with stock pistons to bend/break stock rods. Therefore it is a little bit dumb to install a thick HG on a b6/bp motor in order to run even more boost/hp. If your plan is to run more boost on our motors to NEED to run a thicker HG, you will also need to install forged rods. Which in this case you would be stupid to not install dished pistons at the same time, cast or forged.

I hope that helps. I rarely feel inclined to type this much for someone I don't know.

good write up. I will say though from what i have heard in the past from the honda ricers way back when, is that the science behind the head gasket was to lower compression to put less strian on the connecting rods. I personally don't see a 9:1 comression ratio high enough to warrent this mod. On a bp engine even if you did drop the compression to say 8.5:1 i still think the rods would go before the pistons. The one internal mod that is needed to break 250whp safely is rods. After 280-300whp pistons. thicker head gaskets are just a cheap way to maybe squeeze an extra pound of boost out.