mikemassi

I have a 94z a4 with stock bottom end and cc503 cam. I'm pulling my heads to have them ported and milled. The machine company says he can mill the heads to what ever chamber size I want. I would like to raise the compression of the car. What would be a safe size to get them milled to? 50cc? And does anyone know what 50-52cc would raise the compression to with stock pistons? And what would the down side of raising the compression be?

RamAir95TA

Milling is not the correct way to increase your compression. Use the thinnest head gasket you can use without screwing up your quench. The HP gained will be negligible.

You should only go as much as it takes to true up the mating surface. Generally anything more than .020" will also require machining of the intake manifold. I usually advise .005" at a time which will allow for future "skimming" if need be.

Who is porting the heads?

mikemassi

AI is porting the heads. So I guess since you say combustion chamber size makes no difference in power, what size should I get them milled to?

Injuneer

You aren't milling to a specific combustion chamber volume. You are milling the minimum thickness required to achieve a truly flat surface.

redline9570

I am sure that tweedle-dee and tweedle-dumb know what your’e talking about but to make themselves feel self important they will dig into your lack of technical terminology. I gathered you want to raise your CC and you were asking how to go about it. If your machine shop doesn’t know that maybe you should go elsewhere’s.

Injuneer

Am I tweedle-dee or tweedle-dumb?

Actually, he was asking about milling the heads to REDUCE the combustion chamber cc's.

The next time you lay down another insult, you will be gone from this site.