I have just finished up hand porting my own heads and will be taking them to a machine shop to have a 5 angle valve job and the spring pressures setup. The machinist has recommended that while I have the heads off he could flycut them to add some more compression. I have searched high and low but can't seem to get that warm and fuzzy, for how far I could safely go. I will be running 228/228 duration, .571"/.571", 112lsa +1 cam on a set of stock 241 heads. Can anyone confirm if .025 will work? I want to stay on the conservative side.

Any help appreciated!

 

You didn't mention what valve sizes your using, but if they're stock, you could safely mill .030". With 2.02" valves you could mill .015". Any more that this is going to get risky.

Good luck,

Richard

 

Richard thanks for your reply, the valves will remain stock and I will also use the stock GM head gaskets. Seeing as the opinion is coming from West Coast Cylinders, I feel confident that .030 it is the way I will go. Will there be any problems fitting the LS6 intake back on? Also do you happen to know what the compression will end up at? or possible HP gains?

 

Flat milling each .0065" will reduce the chamber 1cc. We've flat milled heads .045" without manifold fit problems. Anymore than that is going to cause problems with the dowels seating into the heads. Some guys have filed the dowells down to fit into the heads and are running without problems. Milling .030" should get the compression ratio above 10.6:1.
I wouldn't hazard a guess as to the hp gains from compression increases alone, but overall torque should be up across the rpm range.

Richard

 

Thanks again Richard!

Robert