When I rebuild my LS-6 crate motor this year I have been thinking about switching intake manifolds.It currently has a GM aluminum high rise dual plane # 3933163 that was used on the early L-78 375 hp 396 and also the L-72 425 hp 427.I am pretty sure that GM still use this design on their newer big block crate motors.My thinking is that I would like to stick with a dual plane intake,mainly for bottom-mid range and all around driveability on the street.How does this 40 year old design compare to the Weiand Stealth or an Edelbrock RPM Performer ? Has anyone here done or seen any tests on this ? Hood clearance is also an issue,so an Air gap type probably wouldnt fit.

I like the air gap manifold myself. But if hood clearance is an issue, the hp range you're working in, the GM one isn't a bad manifold.

Not sure what your clearance is like, but I just switched intakes for my new build and have a real clean Weiand Stealth I was thinking of selling off my 454 (square port). I can help you figure if it will fit if you're interested.

Good luck in your search.

chris

Yes I might be interested,only thing is that my car is in storage for the winter,so getting measurements could present a problem.Although I dont think there is any height difference between the Stealth and the GM model.But that would bring me to the question of why do you want to sell yours ?
Guy

Thanks for the offer Chris,but that still leaves me with the question of how much better is an aftermarket intake compared to my original GM peice ?

Guy

Unfortunately I can't answer the better or worse question. I have heard and read nothing but good about the Stealth. I can tell you I went to the Vic Jr. for this build as I was looking to get the most from my cam and heads (afr heads and UD Harold SR cam, 255 @.050 and .725 lift). The difference may prove slight though. I also did not mind moving the power and torque up slightly as this thing will be a handfull off the line. I found a great deal on a used Vic Jr. that had been port matched, etc so thought I'd give it a whirl. Plus I have a little room to spare under my hood...and the Vic I bought is ceramic coated and looks cool ;) I admit I'm a slave to fashion.

I would just keep the Stealth to compare but I need the $.

Hey Guy;
I have a Eddy RPM Performer on top of my L-72 427 in my '68, with a 3" filter element the top of the breather cover rubs the underside of the hood ( I switched to a 2.75" element, it clears now). So I would say that an Edelbrock is a taller intake then the original GM intake, as far as a performance difference I have no knowledge....sorry