Aftermarket FE heads seem to be duds according to flow

[ecp]

I made the following graph comparing an essentially stock original MR aluminum C5-H comp Cobra/GT40 head to the common aftermarket items. The -H head does not have any port work, other than a very minor blend of the seats into the bowl, and has 2.19 intake, 1.75 exh titanium valves. The aftermarket heads seem to be quite poor considering they've had 35 years of technology to take advantage of.

[Jeff Frigo]

ecp:

I have a set of Edelbrock heads with the same size valves as your medium risers do. With $1,000 worth of porting they flowed 335 cfm and 240 cfm @ .650 lift.

Made 585 hp @ 6,000 rpm on pump gas with an Edelbrock dual plane intake and solid lifter (no roller) cam.

[DougD]

Good post. Like always, you get what you pay for.
One question, though. Got any original MR aluminum C5-H comp Cobra/GT40 heads in that parts stash of yours for Edelbrock's price of $1300? $2500 like the Shelbys?
Didn't think so.

[Anthony]

Thanks for posting the graph.

I've heard that the factory aluminum heads are thin, that is that their deck is thin, as they supposidly were made with iron head molds. From my understanding, the newer heads have thicker walls and decks, and maybe better for porting and more extensive modifications, possibly with better performance potential than the original aluminum heads, both the med riser as well as the tunnel ports. Maybe you could elaborate.

[ecp]

The decks were thin and Ford did put a small bridge across the long water passage at the ends of the alum MR heads to help reinforce it (marginal fix). Ford documents also show a revised torque procedure was required to avoid cracking the alum heads. The real improvement came with the tunnel port engines which were mostly dry deck, so they were stiffer around the cylinders without the deck water passage holes. A guy in Mass is running these with four (4) holley 4 barrels, twin Paxton superchargers and nitrous even (almost 900 HP w/o the nitrous) and the TP heads are doing fine. You are probably right with regard to the new heads being better for extensive modifications - as you saw one of the previous responses, someone sank alot of $ into the new heads and got them to flow decent......the big desireable aspect of the original heads, of course, is that they are original (for the select group of individuals that appreciate it). I put the graph up as I just thought some people would be interested in subjective info, as opposed to hearing hype from those trying to promote the products