i have a 5.3L engine without heads,, the heads that i have are the 317,, how much do i need to mill them out?? it will be NA engine

 

Dish piston 5.3 or flat top?
317s have a big chamber 71cc

 

Why not just put 243's on?

 

it has stock dished pistons.. my 5.3L doesnt have heads, and i have one pair of 317 heads on my garage, and if is posible to mill them to fit the 5.3L and keep a good compression for NA that will be great, or if someone want to trade heads or something like that?

 

.045 will give you about stock compression.....

 

You would have to shave them down .060" to achieve the 61cc combustion chamber volume equivalent to that of a 706 or 852 truck head. It's not worth it if you ask me.

.006 Milled equals about 1cc less in the combustion chamber. Therefore, .045 mill = 7.5cc less, putting you at 63.5cc. Slightly less volume than a factory LS2/6 "243" casting, but still more than a factory 4.8/5.3 head.

You would be better off to sell the 317s and pick up some 243s in my personal opinion. We sell a CNC ported 243 for $1120 + shipping for the pair, FYI.

 

You could have the 317's sent out to a company that will re-size and re-shape the chambers for higher compression and more squish/quench area than stock 243 heads have, as well as being optimized for a 3.78" bore. May end up with a smaller intake valve than stock though, but with the correct Valve Job, valve de-shrouding in the chamber, and blending into the back of the bowl and short side radius you'll probably see a nice pick up in power/torque.