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Re: Maxing a 318 poly help

From: panic
Remote Name:
Date: July 10, 2003


Can't see any reason not to do it. Usual basis is dual quad manifold, even a factory 2 X 4 iron manifold can be ported out in the middle and have an adapter plate bolted and gasketed on top to support the blower case and channel the discharge into the runners. A thick plate is attached to the manifold to serve as an adapter to the blower mounting pattern and a transition piece for blower discharge to enter the manifold. To figure out plate size: Length = blower case base bolt pattern + 2". Width = same Thickness: should be enough for beam strength (won't "bow" or flex under tension). Steel will work but HEAVY. Aluminum 6061 would be my choice - it's weldable, machinable, easy to find. I'd try 1". That'e enough to counter-sink nuts going on the studs from the original manifold to create a flush upper surface. Begin with the original 8 carb studs (unless they're way inboard of the blower discharge). You may want to drill and tap the upper manifold surface for larger 3/8-16NC studs. You have to figure out what shape (roughly rectangular) will be a compromise between the entire blower discharge and a hole cut out of the original 2 X 4 pattern. If the blower is bigger, you may get better results from a thicker plate (or 2 plates) to use the thickness as a transition. Look at other blower manifolds for the same blower type - see where they put their discharge vs. intake area. When you know where to position it, tap the plate 3/8-16 for 8 studs (6-71 etc.) in the blower base pattern (or whatever size will fit). I don't think the plate needs to be bigger than 15" X 12". This size 1" thick will cost about $45.00 cut to your size, weigh 18 lbs. (1/3 removed for openings? = 12 lbs.) The blower drive nose length will determine the fore & aft position of the blower case on the motor the pulleys must line up no matter what. There are different length nose extensions to position the pulley at different distances from the front cover plate. These are available from Weiand, etc. Radius the opening in the bottom of the plate if its smaller than the intake manifold opening. Better low-speed operation from leaving the center divider in place.


Last changed: July 19, 2018