Apparently the intake GM offers with their ZZ383 doesn't clear a 1981 stock hood, from a comment I found on the internet. And I want to use the original air cleaner, with the fresh air duct from the radiator cover.
I didn't realize until now the vortec heads raised the intake manifold mounting height. Although I suppose that in part explains the additional horsepower.
"This is the perfect intake manifold for a GM ZZ383 crate engine. The intake ports on the ZZ383 GM Fastburn Heads are very large and all the aftermarket manifolds I tried would not cover the ports. This manifold fit beautifully! Being a dual plane design makes this manifold work great through the entire rpm range of the engine. Hood clearance was still an issue on my 81 Z28 Camaro forcing me to replace stock hood for a raised cowl induction hood."
And convert my Q-jet to electric choke But I don't think that will bother me too much.
I did gain some hood clearance when I had my Z apart for painting, by cutting a hole in the hood under the fiberglass hood scoop. I think that got me another 0.5" of clearance, with the stock air cleaner top shape. I'll do some measuring, and see how it looks. The 8 inch height of the #2116 manifold seems about the same as the GM dual plane aluminum intake I have on there now(old L82 Corvette intake, I think), and the air cleaner fits okay with that. As soon as this stupid subzero weather gets out of here!
How about GM 12496820? Low-rise, EGR provision, spreadbore pattern, comes on the HT383. I suspect it is a copy of the 2116 (i.e. Edelbrock might be the OEM). Though with the pad height at (A) 3.87", (B) 5.28", that's still 1/2" taller than my 2101 at 3.5/4.6... and it BARELY fits under my stock hood. I am using a 1/4" thermo gasket carb to intake, so I could get 0.2" back there. But still...
Weiand 8121 comes in at 3.4/4.5, that ought to do it, but no spreadbore...
Yes, that's the one I would substitute for the single plane manifold that comes with the ZZ383, so I can use my Q-jet. But I have a hunch it's not any lower than 12366573, the square bore GM Performance Vortec manifold, and that guy's comment above at the Summit site said that didn't fit under the hood of his '81Z. I'm not using a thick carb gasket, so I save a bit there.