PRH wrote: ↑Sat Oct 07, 2017 2:49 pm
I doubt I could hand port a set of 200cc SBC heads out to 240cc, along with a similar amount of reworking of the ex ports, and the chamber mods in 16hrs.
But......I'm getting old and probably don't work as fast as others.
Then there's the welding up the spring seats....... And tubing the head bolt holes.
I'm just wondering what the consensus is on how much better they'd have to be than what's available off the shelf to justify the added work.
I will say that Carnut has shown some real tenacity in reworking these heads.
Looking back at the numbers from page 1....... 290 @224cc's....... I'd have patted myself on the back and called it "good to go".
Depending on your cubes and RPM you probably would never need that large of a runner, 2 friends of mine did 421's with moderate heads, one was an out of the box 227 AFR pre eliminator that flowed about 309cfm on my bench cammed for NOS per DV's cam master and dynoed near 650 horse straight motor, shifted at 7000 and went through the traps 1/8 mile just over 6800.
The other was a ported Track 1 head, I think in the 230 range but it's been a while since that discussion happened, it was a little better though out and dynoed 675 straight motor.
If I was to try to go 240 cc I would probably start with a 220is runner, I think the 230 has to low of a short turn but I could be wrong.
A mildly worked 200cc head with a 2.08 valve will flow in the 300 cfm range at .700 lift but would be sized for smaller ci of course.