i have been wondering how would this do on my truck. ported and polished my 862 heads along with the combustion chambers and have a 3 angle valve job. vs. 243 with the same work. just wondering how it would flow and if some or any hp/tq would be gained or lost. and upgrade Intake valves to 2" and Exhaust Valves 1.55"

 

The 243's would also have to be milled or you'll lose some compression. I don't have HP numbers. But I know that the 243's will flow SUBSTANTIALLY better than your stock heads.

 

i gained 52 wheel hp with the NNBS topend and just milled 243's ... im running a tr220 cam on a 5.3 lm7. night and day difference..

 

Are you serious? Changed from 862 to 799. That's it, and went up 52rwhp??

 

The NNBS top end he mentioned has a better intake manifold with a larger throttle body, and that would have also contributed to his gains. A better match for his cam.