Picked up the Holley HP main body “upgrade” for my 67 383. My old, tried & true 850DP has 8 screws from the baseplate to the main body & the new HP has only 6 bolts, 3 on each end & none between the barrels.

I’m getting a whistle now at idle & have sprayed the base to body gasket with brake kleen & it will idle up so it’s pullimg air right where the screws are no longer holding it tight.

Has anyone had any issue with these new mainbodys on old baseplates?

They haven’t used the two “inner” screws on the sides on anything in probably over 30 years.

Those two screws are exposed with most single plane manifolds, so they stopped putting them in....... that way they can’t fall out and end up in your motor.

I don’t recall seeing the holes for those screws on any of the newer design main bodies, and the billet base plates don’t have the holes either.
Three in front, three in the rear.

Maybe your baseplate is out of square or the alignment pins are too high, holding the main body up.

Gotta check the heads,intake manifold , carb{s} and exhaust surfaces for square.

if I had a blower like that I would need a cigarette to lots of cool shiny stuff would love to have something like that under the hood of a car one day

Straightedge the baseplate and the body. Especially the bottom of the body across the screw holes. Not unusual for them to get high spots around the screws. Comes from overtightening. Chuck it in a vice and use a nice fine flat file to knock the high spots down.

I've seen that happen, too.

I had an early Proform center that located the metering block a tiny bit lower, resulting in it pressing against the rear vacuum nipple boss. A little filing in the area fixed it.