I have swapped the 799s off my L33 for 07 up 243s I had them milled .20 and I used gm stock head gaskets for the year and model truck it came out of. What will have changed as a result of this ?

 

I wouldnt expect alot. If i'm not mistakin they flow similar but the 799's have like 4cc smaller chambers... they might have bigger intake valves too. Why'd you swap them out?

 

799 and 243 are the same.
Just cast by different suppliers.

 

Swapped to the 243s cause the 799s had a few broke exh manifold bolt broke off and the plaxe I got the motor from cratered the threads trying to get them out . I had the 243s off already so I just threw them on cause their the same as the 799s but these were casted with smoother sand molds.

 

You mill roughly .006 per cc so you have likely taken off about 3.3cc from the combustion chambers. Stock 243s are supposed to be 64.45cc combustion chamber. That leaves you at about 61.15cc. Your compression ratio probably went up .4 or so but you should look at the sum of your parts and do the math yourself to be sure. Not a huge difference but might give you up to 2% more power across the RPM range.