I have my heads currently at the machine shop and wanting to know if i should mill them or leave them alone. I have a 408 with PRC LS3 heads and Diamond flat top pistons. Currently with my setup i am using .061 cometic gaskets with .013 pistons out of the hole which gives me .048 quench. The heads are 70cc and i have .200 PTV. Should i mill to acheive less PTV and more compression. The pistons will have 11.8:1, with 66cc heads, so i am currently around 11.2:1. Any help will be greatly appreciated.

 

Id always mill according to ptv clearance, while leaving wiggle room.

I wouldnt mill much, maybe .015

 

Is the .200 PTV, intake exhaust or both? The exhaust is always the one to watch, as it is the one that will hit if it is late (floats). I have run intakes pretty close without problems.

 

I *believe* your clearances should be 100/120

 

It was .200 on exhaust. Tell me if my comp. ratio assessment is correct? My pistons Diamond 11519 are figured at -.10(positive) I have .014 out the hole with .061 head gaskets. Compresssion ratio on these pistons with a 66cc head are 11.6:1, and 62cc is 12.4:1. My heads are 70cc, so what will my ratio be. My quench is .048

 

I'm figuring 11.47. without knowing the gasket bore diameter.

 

Here you go, fully functional compression calc with all the goodies

https://ls1tech.com/forums/generatio...alculator.html

 

Really great app man, my compression ratio is 11.14:1, so we will mill the heads to 66cc, which will give me 11.6:1. Thanks for your help!

 

My best results were with CR in the 11.3-11.4 range. Above that and we couldn't put in enough timing. I ran 12.0 and picked up about 30HP by dropping it to 11:4 and could add 4-5 degrees more lead. These heads lve timing and I learned not the trade compression to timing.

Just my $.02

 

What size cam, if you dont mind me asking