Flow Comparison Between Factory 428 Cobra Jet Heads and Edelbrock FE Heads

[Qikbbstang]

Could it just be the brief but greater intake flow flow where the stock CJ Head intake port out performs the Ed Head comes from the CJ being simply a larger hole to breath through which pays no attention to quality vs quantity. Of course I'm shooting blind in that I have no port volume figures and just presume the CJs volume is larger.
          Ive long wondered if there were a way to truely compare a stock CJ head (low Riser) to a Ed Head (Med Riser) . I think somehow making unique manifold runners low riser/med riser so no steps are involved is about the only way to have apples vs apples
 
http://fepower.net/Dyno%20Results/dyno_results_12.html

[Drew Pojedinec]

I feel like you've brought this up before.

There is a sure fire way to test them both.  buy them, install them in your vehicle, drive around for a week, see which one does better with your engine and sell the other one.

[My427stang]

Well, I am not sure if the source is correct, but Stan Weiss's site shows:

CJ - 152 cc intake and 122 cc exhaust port
Edel - 170 cc intake and 125 cc exhaust port

If those numbers are true, the opening of a CJ may be bigger, but it's choking somewhere else

As far as the Jay's test, it does of course show that the CJ is a decent head, (and may even get better with a good med riser intake port bolted to it)

However, those CJs did have some bowl work, most stock CJs are closer to maxing out at mid 240s and moreover, even with this set, the exhaust is pretty crappy.  Less exhaust means less scavenging and less effective overlap

Needless to say you can make them run, but I think those that do have more in them than the price of a stock Edel

The tough thing about comparing is they are so different in chamber size, that you have to introduce more variables even if you do a direct swap.  In the end,  I think even bone stock Edels are a pretty good deal

[plovett]

I've had untouched factory CJ heads and untouched Edelbrock heads flowed on the same bench on the same day.  I've posted the numbers several times on the FE Forum.  There's very little to choose between them. The Eboks flowed a little more at high lifts on the intake.  The Ford heads actually flowed more at low-mid lifts on the intake.  On the exhaust side the Eboks were superior everywhere.   Now that is just flow at 28".  I don't know velocity, or effects of different intakes, etc.  But on a semi-hot street engine there is not much difference as Jay's testing showed.

The good news is I was so underwhelmed by the out of the box Edelbrocks I had bought, that I had them fully ported by a good cylinder head guy.  Gained about 50 cfm at high lift, which is a lot IMO.

One thing that is not often mentioned is that the exhaust port is significantly affected by compression ratio.  A high compression ratio makes the exhaust port work better as the pressure in the cylinder is higher after the power stroke.  This is like flowing the exhaust port at a higher vacuum.   A 385 series ford is a better example as they have a better flowing intake port and a worse flowing exhaust port than FE's.  Build a low compression "smogger" 460 and it can be a dog.  High compression examples run very well and equal or better similar BBC engines despite having a "horrible" exhaust port in comparison.  I'm thinking that the out of the box Eboks would have a greater advantage on a low compression truck or cruiser motor.

The main advantages of the Edelbrock heads are that they are new, cost effective, and since they're aluminum they're easier to port. 

The dyno (or the stip) is the ultimate flow bench.  I wish I could've compared them that way.  But in general, Eboks and factory CJ's are about equal.

JMO,

paulie