[4zpeed]

Seems I did find a discrepancy in the earlier post, "251 cfm plus 706 cfm = 951 cfm", (corrected = 251 cfm plus 707 cfm = 958 cfm).

355 cfm at 3" divided by 1.414 = cfm at 1.5"
or 251.0 cfm at the 4 bbl rating.

500 cfm at 3" divided by 1.414 = cfm at 1.5"
or 353.6 cfm at the 4 bbl rating.

353.6 x 2 for the end carbs
or 707.2 cfm at the 4 bbl rating.

251 cfm plus 707 cfm = 958 cfm by the 4 bbl rating.

958 cfm by 4 bbl rating x 1.414 = 1354.6 or 1355 by the 2 bbl rating.

As mentioned though the 1.414 is a good conversion, but just gets us in "the ballpark", it does however allow us to avoid the pitch of (Advertised) cfm.


I may be off base here but in the latter equation something doesn't seem right.

So, assuming they used the same method in (Advertised) cfm, and using your formula for each, wouldn't the 850 venturis have at least the same or larger (Actual) difference in cfm than the 750 venturis?

I'm asking because you stated "The venturis on the end carbs are 1-9/16" or 1.5625" for the venturi size (Same as a 850 cfm Holley carb venturi) but at the higher test pressure would flow more cfm."

251 cfm (the 1.414 conversion) vs 373 cfm (the actual calculations) = 24 cfm difference.

958 cfm (the 1.414 conversion) vs 963 cfm (the actual calculations) = 5 cfm difference.

This situation with advertised cfm for carbs is much like the advertised duration of cams, fubar.


Much Thanks,

Frank