I have two sets of heads that I could use on my 496 build-up - a set of Merlin oval iron heads and a pair of GM's aluminum heads with the "roval" ports. When I check the Chevy Hi Performance website and look at the flow numbers on their database, it looks like the Merlins stay with the GMPP heads right up to about .600 lift, which is where I'll top out. How can these flow the same when the GMPP head's port is 292cc and the Merlin is only 260? If these figures are accurate, the velocity would have to be much more thru the Merlins and they'd be the easy choice. The GMPP heads come with a factory bowl blending and the Merlins are out of the box rough, so they'd pick up more with a light cleanup. I hate to get hung up on numbers, but I'm kinda stuck here. This will be for a 3500lb street/strip ride, looking for 600hp or so. Any help or real-world experiences would be appreciated!

[ 07-18-2003, 03:42 PM: Message edited by: MyBoTy ]

that magazine data is worth very little, it's fun to look at but I wouldnt trust it for a second.Talk about a conflict of interest, the advertisers pay big bucks to the magazines, they are not gonna publish unfavorable data on thier products. They didnt test YOUR heads anyway (even if you could trust them to be accurate, they tested A head but not YOUR head. Just the valve job alone can make a huge difference in flow numbers. It's even possible that the lower flowing head between the 2 types you have could make MORE power than the higher flowing head.

The best thing you could do would be to try BOTH heads and compare them yourself on YOUR combination. Most guys on here are not luck enough to even have two pairs of performance heads to compare. Take advantage of that.

Doug ( stepping off my soap box now) J :rolleyes:

I agree, unless the tests were performed on the same flow bench on the same day by the same operator....well dont expect an apple to apple comparison. The other part is there are two differnt GMPP ROVAL Big Block heads. One with 2.19 intakes and another with 2.25.

I have not tried the merlins but I have a set of GMPP 2.25 on a warmed over 427 http://img.villagephotos.com/p/2002-11/70533/Jul0202.jpg To be honest I dont think you could go wrong with either. I think there is a slight advantage to the GMPP part due to the aluminum custruction and a few minor things.

I am impressed with how well they work. The craftmanship is great.

By the way you know they are made by Edelbrock right? They are the same base casting as the Edelbrock Perfomer RPM head. It just it has "GMPP Signature Series" on the end instead of "Edelbrock".

I wonder why the Edelbrocks are about $200 a head more expensive then the GM's :confused: .

http://www.paceparts.com/product.asp?0=243&1=246&3=511

Jegs price for the Edl. are $860.

Wait,

I think the link above may be for incomplete heads, and this is for the complete ones.

http://www.paceparts.com/product.asp?0=243&1=246&3=509

FWIW that flow data on the CHP site has been proven in several cases to be fairly accurate. There were a couple tests by builders on this site that had results that paralleled the flow data --- the heads that flowed the best seemed to make more HP on the dyno. Its alll subjective but I thing the flow data is a good place to start.

I have good things about the Merlins on the Chevelles.com site, but there are a lot of "iron only" guys over there.

For the money, and only that, the Canfield aluminum heads are generally a good buy, but they are, I think, small rect's in the 310cc range!

FWIW, I would think they would be just about right when the dreaded, "more power, Scotty" bug bites!!

Let's please not get started on the al/ci, rect/oval thing here....

As always, jmho. pdq67