Hallo,
I have to take my zylinderheads off from my 1973 Devill with the 472cid engine. I´m wondering to what compression ratio I can transform it when using 95 octane gasoline. Standart is I think 8.25:1. How much can I take off from the zylinderhead?
How much horsepower can I get with 10.0:1 compression?
Has anyone polished the intake in the head or eaven madem it bigger? What else can I do to get a bigger performance with modifyng the zylinderhead?
Greetings
Patrick

First, it's cylinder, not zylinder. Running 95 (r+m)/2 octane would probably be fine with 10.5:1 or so. Unfortunately it's not really possible to mill the heads to make such a change in compression, you would have to swap in differant pistons. You can have bigger valves installed and port the heads for more airflow, but porting isn't easy. Porting is time consuming and it can be difficult to get all the ports the same. A camshaft will definately help performance, especially if you do head work. Don't neglect to think of the intake and exhaust manifolds - you could modify your stock intake manifold for more performance or buy an Edelbrock, and you could do headers for the exhaust.

port matching is an easy way to get a little extra from the heads, and isn't too hard either.

Dave is right to get a high CR you would either have to swap heads to a smaller combustion chamber or put new pistons in the engine.

Your best bet to get a little extra from the engine would be to put and edelbrock intake, a cam, and if possible a set of headers on the engine to get some power. and if you port matched the heads and intake that would help air flow.

however if you are set on grinding on the heads if you are a first timer it would be best to just smooth out the intake and exhaust. but you can't make the intake ports really smooth they have to remaina little rough. but getting the exhaust ports smooth like glass helps flow a lot.

good luck :thumbsup: