Eliminating the stock valley-pan gasket can be an advantage where heavy milling of the block or heads renders poor alignment with the stock pan. Also, the pan is simply an embossed steel gasket, questionable in its sealing ability with anything but the heavy factory iron intake on iron heads. Porting the heads reduces the available sealing area, further compromising the seal. Thin paper gaskets can be added to enhance sealing with the stock valley pan, but we think that six-piece gasket setup is garbage. Finally, to end this valley-pan tirade, the stock steel shim gasket, with its efficient thermal conductivity, adds a surprising amount of heat to the intake via the heads. Not good. We don't know if Edelbrock plans to offer an aluminum valley cover to go with their heads, but it would be simple to fabricate them at home. A valley plate combined with a composition intake face gasket seems like the way to go.
As of our visit to Edelbrock, the heads were being prepared for dyno evaluation on Edelbrock's 440 Chrysler research engine. The engine is already fitted with a nicely ported set of production iron heads, so the new Performer RPM heads have to work to prove their worth. We expect the heads to be released through Edelbrock retailers by the time this issue of Mopar Muscle hits the newsstands. We're already planning to build an engine and do our own dyno testing. At Edelbrock, we had a chance to flow the new heads, and the results showed substantial flow. Want an affordable trick aluminum head to top off that old Mopar? Edelbrock's got your engine covered.
Show Me The NumbersHeading out to the Edelbrock plant to get the scoop on the new big-block Mopar heads, we took a virgin 906 casting, along with the necessary flow-testing apparatus, and tossed them into the trunk of our Edelbrock-headed small-block '69 Dart. The head, off an untouched low-mileage '69 440, still retained its production machining down to the factory valve job. The seats were in outstanding condition, at the factory height and width, with the production valve sizes of 2.08-inch intake/1.74-inch exhaust. The head and valves were just cleaned spotless, with no flow-enhancing mods or flow-robbing carbon buildup or dirt.