Quote:
Originally Posted by PRAY
You made a good point about C/D or coefficient of discharge. Using the heads you described above. Brian Tooley did a good write up about this. I ran the TFS 235 heads on my 02 Z06. 416 with a 247/254 112+2 cam and a FAST 92. The car made 573/530rw. It ran 10.20@136 wiht a best mph of 138. I took Brians advice and designed my own stock 243 runner with 2.04" valves. I got them to flow 240cfm at 235ish cc's. In my Gen 1 CTS-V with a LS3 427, stroke not bore, 243/251 113+4 cam and a FAST 102 I made 570/525rw. So a much heavier drive train with a smaller cam made the same power with 10cfm less flow. It did have 10 cubes but a better C/D. Now I have that same cam in another C5 with my LS3 top end that flows 380@.700 and it makes the same power. So all that extra flow and a much better flowing IM didn't make a difference in power. I think those heads flow 330cfm with the ported LS3 IM attachedon my bench. Head alone on my bench goes 253cfm at .700. I am pretty sure my ported Fast hit just over 290cfm on the LS2 heads. I have perfected my LS2 intake and exhaust ports since those heads. They flow much better down low now and the exhaust is leaps and bounds ahead. I have two motors coming out soon. A 429 in a truck and a stock block A4 LS2 GTO with my ported LS2 heads. We are trying to break 500rw on the stock short in the GTO. The heads I just finished up for that build flowed 300cfm through the ported fast on my bench. My bench is down 30cfm to the 28" bench on my LS2 stuff. So velocity and C/D are very important to over all power.
I will admit that I am crazy temped to throw a LS3 valve into these LT1 heads and see what happens. They are 10g lighter and would provide probably another 10-15cfm down low. They fit on the stock seats as well. Would be a curious test to see what they would do.
The point is to keep the port as small as possible cross section wise with the correct taper and a bunch of velocity, tumble and swirl. |
What about GMs CNC ported heads?