Thinking of milling my 243 heads but not 100% sure as to how much I should take off. Want it to remain 93 octane friendly, I'm thinking .02, how much compression would that net?
Stock is 10.5 right?
Doing some searching & I think using a stock type head gasket CR will be at 11:1
Dont think I want to go more then 11:1.

 

Another question I have is since the block is an LS6 with flat top full float pistons will milling the heads .02 create any piston to valve interference issues?
Going to go with a cam in the 580 lift range.

 

you should have no problem with PTV milling the heads. .02 ,as long as you get a cam with the proper timing events and install it correctly.your tuner can monitor the spark knock sensor and adjust timing for max power with out knock.

 

Thanks whats a good price to mill the heads .02?
Machinist wants to charge me $200, is that too much?

 

What are the specs on your cam? Lift really has almost nothing to do with p to v on these motors, its in the duration. You can run up to 11.5:1 on these motors before pump gas becomes an issue. If we are just milling heads we usually charge around $100.

 

Thanks for the info John, cam choice has not yet been made, wide open right now. Currently I have 243's with springs that have a blue marking on them, was told they would be good for +-0.6" of lift, thats why I'm thinking of a cam in the 0.58" range.
Am I making the correct assumption on the springs?

 

those blue springs are probably off a ls2 and not good for a cam over .550.have them tested to see what spring pressure they make at .600..I would never use used springs on a new cam.you can get new springs at TSP.if you don't get your heads milled use a thinner head gasket.

 

Darn it, was trying to avoid getting new springs!
Guess its better to know now then later.
Guess I can go with a bigger cam now then!

 

Stock chambers measure 64.45 cc volume which computes compression
at 10.45:1.....approx .007 mill equals 1 cc....so .020 will put the chamber
at about 61.55 cc......I figure 10.83 with stock gasket
Always match NEW springs with a hopped up cam...TSP has nice kits

 

Yeah, I believe generally $100 for the set is normal for around here. Though labor in different regions can vary I'm sure.

You may want to look into the yellow '02+ GM valve springs. They're supposed to be good for more lift (~ .600") than the blue stripe ones and they're reasonably cheap ($60 or so). If the blue stripe springs you have are new, you can probably sell them and not have much money in the yellow springs.

 

The GM springs are definitely budget friendly but they also limit your cam
selection since they lack the neccesary pressures to work with some of
todays more aggresive lobe profiles. Not saying don't use them just make
sure to pick a cam that will work w/the lesser pressures.

 

Really Claytonisbob, that is very interesting information, had not read that so far. Definitely sounds like the right course of action especially since I wasn't planning on going over .6" of lift. Would those yellow springs be a GM direct part? if so anybody have a part number? Thanks a bunch this very helpful information.