Here's an interesting dyno shootout 160 cfm head on a 306, 333 & 393.

[273]

The 160 cfm heads made 1.91 hp per cfm on the 306 (306hp), 2.2 hp per cfm on the 333 (352hp) & 2.41 hp per cfm on the 393 (387hp).

They all had different cams, got larger as displacement went up which would also be contributing factor.

Be kind of like if we did a 318 vs 360 vs 408 with stock 318 heads.

 

[ch1ll]

Way cool.

 

[273]

Way cool.

I thought it was pretty interesting myself.

I'd like to have seen them with the exact same combo on all 3.

 

[RAMM]

I thought it was pretty interesting myself.

I'd like to have seen them with the exact same combo on all 3.

Haven't watched it but 2.06HP/CFM seems to be the sweet spot at least for me. Those HP levels you quoted are not impressive at all. While I agree its interesting it just isn't any kind of mystery in my eyes. J.Rob

 

[273]

Haven't watched it but 2.06HP/CFM seems to be the sweet spot at least for me. Those HP levels you quoted are not impressive at all. While I agree its interesting it just isn't any kind of mystery in my eyes. J.Rob

I don't think the hp/cfm level are impressive in themselves. Just how the 393 could squeeze another 81 hp out of a ridiculous small head over the 306, even though I imagine the 248 solid roller vs 212 hydraulic roller did play a big part but doubt it was responsible for the total gain. Just thought it was interesting.

But the 2.41 hp/cfm 393 engine did gain a 168 hp when he did put on proper heads on it, 387 vs 550 hp.

 

[RAMM]

I don't think the hp/cfm level are impressive in themselves. Just how the 393 could squeeze another 81 hp out of a ridiculous small head over the 306, even though I imagine the 248 solid roller vs 212 hydraulic roller did play a big part but doubt it was responsible for the total gain. Just thought it was interesting.

But the 2.41 hp/cfm 393 engine did gain a 168 hp when he did put on proper heads on it, 387 vs 550 hp.

What did the 550HP heads flow? J.Rob

 

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What did the 550HP heads flow? J.Rob

He probably did this test years ago, but here's what they advertise now for AFR 205, the cam had .614/.621 lift.

205cc Street Head Flow Chart
......200.300.400.500.550.600.700.750
Int139,199,251,285,297,308,317,320
Exh121,170,206,219,227,230,232,234

 

[273]

What did the 550HP heads flow? J.Rob

Even the other two engines 306 & 333 gained like 80 hp over the stock head and gave up almost nothing, even though you can squeeze some power out of the stock head, shows really how much you can be holding your engine back 80-168 hp with stock heads. These engines got an Edelbrock and Trick Flow upgrades.