compression with milled 243's ???
 

I may be picking up a set of 243's milled 0.020" for my stock LS1. Any idea what the compression will be compared to the stock configuration with 853's?

On a side note, what kind of power improvements could be expected with the milled 243's and a LS6 cam? This is going into a 95 mustang, just looking to have a fun daily driver.

243 heads milled .020" would be right around a 61cc chamber. The stock 853s have a 66cc chamber so that would leave you at about 10.9:1 compression according to my calculator. With the addition of those two parts I would be looking for around a 30rwhp pick up.

I'm assuming this is still a pump gas safe setup, is that correct? I'm also assuming that flycutting the pistons isn't necessary for this combo, am I still on the right track here?

Also, aside from new push rods of an unknown length, a timing chain, bolts & gaskets is there anything else needed for this swap?

That should be pump gas safe no problem, you can usually go up to around 11.5:1 on pump gas with these motors. You would not need to flycut as the LS6 cam will leave plenty of clearance. Looks like you have a good grasp of what you need for the swap, the only thing I saw missing was an aftermarket oil pump, and some lifters. Neither parts are required but always something to look at doing when you are doing this much work.

I'm interested too in milling some 243s, which is the head that I'm told comes on L33s.
How much can 243s be safely milled and how much would that raise the compression on an L33 5.3?
Thanks
Jarhead

Roughly 0.0065" mill equals 1 cubic centimeter of volume
each cc of reduction raises the compression about 0.120 points

Ok thanks for the info but how much can those heads be milled safely?
I'm looking to raise the compression about 1 point and hope it can be done safely.
Jarhead

Some have milled stock castings as much as .040-.050 but not only will this
change the pushrod length but it can cause intake manifold (dowel) issues.
243s stock bump you from 10.19 to 10.45..then with a .020 mill you'll be close
to 10.8