[wayniji]

Hey - Was wondering if anyone had a good resource to find out how many CFM a set of BBC heads (casting number 3856206) flow?

Or if you have had first hand experience with the performance of these heads. They have been cut out to 2.19 intakes.

Thanks

[BBCMudbogger]

I could be wrong, but I beleive a stock oval port is about 250cc

[techinspector1]

Here's some flow info from a guy who just got his heads back from the shop.......
http://www.camaros.net/forums/showthread.php?t=39718

[454C10]

I had a set of 71, 402 bbc heads (820??) rebuilt with 2.19/1.88 valves and did a little bowl smoothing. The chambers are 112cc, ports are 240cc, intakes flowed 260 cfm at 0.500" and exhaust 199cfm at 0.500". These are the heads that the chamber is not angled toward the exhaust valve which makes the exhaust flow much better.

I also have a set of 781's with 123cc chambers and 255cc ports. I also put in larger valves and smoothed the bowls. I also unshrouded the valves by moving the chamber walls to the gasket near the valves. However, I never had them flow tested. I would bet they would flow at least 275 cfm at 0.500" on the intake and 200 cfm on the exhaust.

[BBCMudbogger]

Just adds a littlle fuel to the sb vs bb debate. 250 stock CFM for BB vs 220-230 for an aftermarket sb head....hmmmmmm I have a set of closed chamber 063 ovals for a 396 w/ 2.19 1.88s .Havent had them flow tested and don't even have the engine finished yet but I think I'll put my little 414" bb against a 383 sb any day.

[454C10]

Yes, bbc heads flow nicely in a stock config. People will say, "will sure they flow well but look how big the port is". The main reason the bbc port is so much larger than a sbc is because the ports are longer not because the ports are wider. Sure they are a little wider also. But, when looking at flows numbers the cross-sectional area should be considered. The number you really should be looking at is flow/port cross section area (cfm/inch squared).

SBC AFR heads flow as much as a stock bbc head with a lot smaller port. I don't know how they do it but it is almost unbelievable.

[techinspector1]

Originally Posted by 454C10

Yes, bbc heads flow nicely in a stock config. People will say, "will sure they flow well but look how big the port is". The main reason the bbc port is so much larger than a sbc is because the ports are longer not because the ports are wider. Sure they are a little wider also. But, when looking at flows numbers the cross-sectional area should be considered. The number you really should be looking at is flow/port cross section area (cfm/inch squared).

SBC AFR heads flow as much as a stock bbc head with a lot smaller port. I don't know how they do it but it is almost unbelievable.

Excellent post.