Has anyone flow tested the stock cast intake manifolds for the 68-69 383's and 440's? Castings 2806301 and 2806178. Thanks.

Not exactly what you're looking for.... If you do find any flow numbers, please post.

Link

I think Andy F actually did some intake flow testing, but don't know if it included the factory manifold. Hughes might have as well. Maybe check their web pages.

Certainly the FAST guys have.

Thanks for the link....the comparison test results are interesting.

I did come across the testing done by Hughes, very good information but no testing on the stock 4 barrel castings. They state that an intake manifold should flow 16-20% more than the cylinder heads.

http://www.hughesengines.com/TechArticles/4portedintakemanifoldsupdated08272007.php

Hopefully some from FAST will have some information.

IIRC a stock iron intake is around 200cfm.

Thanks, that sounds right........a little restrictive when matched to the stock cylinder heads.

Correct. I knew I had the tests in a file somewhere. Here are three flow tests done on the same day. (1) Ported 906 cylinder head w/ 2.14 intake valve. (2) That same 906 head with the 2806301 intake and a Carter AVS 4401S carburetor. (3) Again the same 906 head, this time with an OOTB 383 Victor intake and the 4401S Carter AVS carburetor.

Lift.........cfm(1)..........cfm(2).........cfm(3)
.100.......71.................69..............69
.200......150...............131............143
.300......209...............172............202
.400......257...............187............234
.500......292...............199............259
.600......315...............203............273
.700......321...............204............273

I tested a bunch of intakes when the FAST thing was going pretty strong.

I had narrowed down/streamlined the process a bit.....

I only tested at a high lift...... .700....... but I tested all 8 holes.
I also used a Holley HP1000 carb to minimize any possible restriction there.

Test all 4 ports on the head, average the results.
Test all 8 intake ports, average the results.

On a 286.7@.700 cfm head, the stock 301 intake was 25.8% lower.
Mildly ported it was 19.5% lower.

An M1 single plane that was gasket matched was 8.2% lower.

When testing the head was there a radius,clay, used on the port ?

C’mon Charlie....... you know the answer to that.

You’re not going to see 286cfm out of a 906 head without an entry radius.

Any head test that didn’t use an entry radius is of zero value imo.

I’ll be testing a head today...... I’ll see how much taking the entry radius off drops the flow.

LOL I know, sorry, I just wanted to make it clear to others ,,

I agree, I also prefer a solid made radius over a clay one for better repeatability , as you know it will drop off a LOT , the sharper the opening edge the more the drop.
I know I'm just preachin to the choir LOL

Flowing 300cfm with the plate on...... removed plate, lost 65cfm.

Thanks,

What brand is your bench ?

Its a Saenz S-600...... which is basically a copy of a SF-600.

10-4

Thank you all for the replies and information.

The bottom line is......... “if you’re trying to make some power”...... the stock non-spread bore iron BB intakes are going to be a problem.

And....... the more power you’re trying to make, the bigger the problem is.