Heads + Blower

I'm aiming to build a 331 (stroked 302, Dart block, 4340 crank + H-beams, dished pistons) for a blown racing application. It will see some street use but my primary concern is the strip (if it doesn't run worth a crap on the street it's no biggy).

I'm currently debating the heads. I can go with aftermarket aluminum heads (AFR, Edelbrock, Trick Flow, on and on) or a pair of D1ZE-DA 4V open-chamber 75.4cc Cleveland heads in my possession.

I'm more interested in comparing performance than price, I'm aware of the modifications needed to the block and heads if going the Cleveland head route (and the Boss-style blower intake manifold), and the weight savings with aluminum.

I realize there are a lot of aluminum heads out there that flow better than the Cleveland heads, at 28" water. Here comes my hang-up- considering this is a supercharged situation, wouldn't the gargantuan intake ports of the Cleveland heads be an advantage here over the aftermarkets? Another way to ask my question is, in a blown engine, would port volume be favorable over port flow?

MM

I would go with some AFR 185 - 205's TFS R heads or Victor Jr heads over the cleveland heads because of the manifold selection will be so much greater (and easier) with the windsor style heads. Also the combustion chamber in the open heads is not very good and is prone to detonation. The fact that they are made out of iron doesent help. THere is also the difference in weight between iron and aluminum.

Thanks for the tip on the detonation problems, that's the first I'd heard of it and will investigate.

I'm still curious about the flow/volume question, even if the answer is simple.

<font size=-1>[ This Message was edited by: MustangMike on 1/14/06 8:35pm ]</font>

Get a set of the new Edelbrock aluminum heads for the 351C and 302/351w blocks. That'll solve all your problems. Blowers need lots of good exhaust flow. Restrict the exhaust side and your blower set up will suck instead of blow. Exhaust will kill HP faster then anything.

The new Edelbrock heads are really a poor excuse for an aftermarket head. With intake flow rates slightly better than a ported iron 2v head, and exhuast flow worse than a ported iron 2v head, they aren't worth 1/2 of what they are currently asking for them.

How about the Jeg's/Kaase heads? Those intake ports are huge (247cc); I'm assuming with a blower I wouldn't have the lower RPM problems a naturally-aspirated engine would have with the same heads?

From magazine dyno tests those heads make some big power. What is this engine going into anyway?

1967 Mustang. If you click on "My Cars" you'll see a picture of it with the motor that is now in the Cougar (less the blower).

<font size=-1>[ This Message was edited by: MustangMike on 1/17/06 8:02pm ]</font>

I have ported Edelbrock heads with 10# Paxton SN2000 on a 349, but pretty much redid the whole head(springs,locks, etc), they have weak springs out of the box and now they flow a little less then a 185 i think, but cost twice as much [img]/phpBB/images/smiles/icon_frown.gif[/img]
[addsig]

Since my original post, I've made a few calls, did some research, and got some more opinions.

Considering my original question (flow vs. port size with a supercharger), according to AFR, "flow is everything, even with a blower." According to BDS (Blower Drive Service), "flow is everything, even with a blower."

However, according to CFE Racing Heads: "When evaluating a set of heads, airflow should not be the first concern. More important is the cross sectional area (which influences how much a port will flow -larger areas typically flow more air) as well as having the appropriate port shape for the application. If any of these are addressed incorrectly, the best flowing head on the bench will never make competitive power."

The cross-sectional area of the Cleveland intakes versus what I'm tempted to go with (AFR 205's) is about 163% larger (2.5" x 1.75" vs. 2.1" x 1.28&quot[img]/phpBB/images/smiles/icon_wink.gif[/img]. Just seems that under pressure, the Cleveland port volumes would pack more punch- but so far I still haven't come across anything conclusive (math) to back that up (any fluid dynamics wizards around?). I'm not knocking the statements by AFR &amp; BDS and don't think they have other motives for telling me what they did, it's just that again I don't see conclusive facts yet to back up their claims.

At this point I am tempted to go with the AFR 205's, because of convenience (I already have a Windsor-style blower intake), they have good flow numbers, and I'd have more torque at the lower RPM ranges, but I am still very interested in the original question and will hopefully stumble onto an answer some day.