ok i will be building a lq4 with 317 heads, i know everyone says go 243 but these are free and for me free is anyway, i will be running a 222/226 eps cam i want to mill the 317s down a little to up compression, my question is how much can i go before i have ptv issues and have to change push rods and any thing else that might come into play. also i want to still be able to run 87 oct if possible or next grade up

 

You want to up compression but use 87 or the next grade up. I'm not to sure about that

 

im new to this that y i ask

 

That's counterproductive. You can run 87 if you don't mill the heads. Generally milling .030 is the accepted amount. PTV shouldn't be an issue with that cam.

 

what size gasket should i run also?

 

You'll want to run the 6.0l gaskets to clear the 72cc combustion chambers in the 317 heads. GM make a MLS gasket or cometic. I run a 4.030 cometic on my 5.7L/317's.

 

Not sure why 87, lol, but I'm sure you could run it if fine if you dont get on it. Lol. Think that kinda defeats the point though?

 

Premium gas isn't that much more expensive ffs. On a fill up, you're gettin maybe 1 gallon less with premium for the same amount of cash. If you can't afford premium gas, you should drive something more economical.

 

Nothing wrong with 317's, they are the Same essentially as the 243, Just with a larger combustion chamber. A good mill and a thinner than stock gasket will bring you right on par with a 243 head.

And I agree, generally premium gas is 20 cents more a gallon than regular. On a typical 10 ish gallon fill up, you Will spend 2 bucks more going with premium, and your car will thank you in the end.

 

That's my question what size basket to run and how much to mill to get me right at the 243

 

It's tough...

.0065 mill is roughly 1 cc. To go from 72 cc's, to 63 ish, you Will have to take around .060 off it, which is a lot.

 

I was told .40 is the most which would be around 65-67 I think which to bad.

 

Just sell the 317s and buy some 243 or 799 heads. The money you save on the more expensive gaskets and milling will help offset the cost differential. Milling that much from the 317s will hurt flow and PTV clearance.

 

Sorry to hi jack, but I'm thinking of sending my 317's down to be milled to bump compression a little. If I have the machine shop take off .040", will that cause any intake fitment issues?