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Username Post: TBI on a Dual Plane Manifold??
1983G20Van 
Super Senior Member
Posts: 3888

Loc: Bedford, Texas, USA
Reg: 11-13-02
11-25-20 09:45 PM - Post#2808626    
    In response to racprops

Factory TBI manifold is a dual plane. The GMPP TBI vortec intake and most aftermarket dual plane carb intakes swap the injectors between cylinder pairings compared to the stock intake. I swap the injector output left and right at the ECM to run manifolds with the opposite pairing. Performer RPM or a single plane like a Torquer 2 is what my TBI engines ran best with. If you run a single plane it is best to setup the ECM to run in Asynch only.

That being said I ran a mercruiser dual plane MPFI intake on the 383 in my Express van. Gave it a signifigant low-midrange torque bump compared to the equal length runner cross ram style L31 marine intake. The dual plane manifold will always give a little more torque with or without fuel flowing through it. The length of the runners offer resonance tuning. Since air pressure waves act the same way as a fluid it can assist the intake charge at lower rpm.

That being said I have run dual planes and single planes on the same Vortec head 350 TBI engine and never noticed a torque loss with the single plane. Had plenty of torque even down at 1,500 rpm. Not like you can really feel 15-20 ft/lbs less torque in a 5,500 lbs van.
1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


Edited by 1983G20Van on 11-25-20 09:55 PM. Reason for edit: No reason given.
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