Milling 317 to raise compression on lq4

[52 Rat]

If I have .030 milled from my 317 heads, what will that raise the compression to on my stock bottom end lq4? I could not find a conversion factor. I don't want to take too much and cause intake alignment issues.

[Shon]

I think most say it gets to the 10s.
www.performancetrucks.net has lots of info

[duwem]

Another option would be to put in LQ9 pistons. LQ9 had a higher CR and I believe it was only because of pisions, not head or rods/crank.

[52 Rat]

Originally Posted by duwem

Another option would be to put in LQ9 pistons. LQ9 had a higher CR and I believe it was only because of pisions, not head or rods/crank.

True, but my engine is low mileage and no real need to change out the pistons, re-balance, etc. As it stands now, I can remove the heads and have a little machine work done.

[68 c10 ls2]

Originally Posted by 52 Rat

True, but my engine is low mileage and no real need to change out the pistons, re-balance, etc. As it stands now, I can remove the heads and have a little machine work done.

If you want to raise the cr i would just find a set of used 243 heads. 317 have a 72cc chamber and the 243's have a 64cc chamber. i would think it would be cheaper than any mill work.

[52 Rat]

Originally Posted by 68 c10 ls2

If you want to raise the cr i would just find a set of used 243 heads. 317 have a 72cc chamber and the 243's have a 64cc chamber. i would think it would be cheaper than any mill work.

I had read that the 243 did not flow as good as the 317's but I don't know that to be true. I thought they were the same design but one having a larger combustion chamber. I'm thinking now I will keep my current set up and my go with twin turbos.