Question about raising compression?

[Mulisha]

Well I actually have a couple questions. What size is the stock head gasket on a 4-AGE? How much smaller of a head gasket do I have to install to actually make a performance gain?

Mulisha

[Aico]

I believe the stock gasket is 1.2mm. So anything lower would have some CR increase.

[Mulisha]

Yeah, thats the size I thought it was. Now if I lower it to .8 or something smaller than that I will see power increase and I shouldn't have to do anything to the ECU or tuning wise.

[s.bjelke]

I wonder how much performance you gain from increasing the compresion like this? like if you change to 0.8mm what will you gain in actuall performance?

[jamiemirror]

Try the 7A head gasket - the stock one is 0.7 mm.
If you change the CR - adjustable timing wheels might be good investment :-)

I think that you will be close to 10:1 CR. A little performance gain - maybe 3-5 hp maximum. But for cheap ;-)

[Mulisha]

Would I have to get adjustable cam gears?

[Aico]

No

[jamiemirror]

2 Mulisha:
Not obligatory, but will help.
When you mill the head (and/or use thinner gasket) you will retard your cams timing. With adjustable wheels you can fix this problem (also when you use different cams) and adjust the timing "1/2 tooth" - for example.

[Mulisha]

Would installing a smaller head gasket really retard the timing that much.

[PetzK]

I once calculated the timing difference with shaved head etc, and I came to about 0.0xx degrees, so REALLY negigeable! thats some 200 bucks for cam gears you can save...