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Thread: Intake Manifold - Notching Plenum Divider?

  1. #1

    Default Intake Manifold - Notching Plenum Divider?

    '72 Corvette 454 BBC. Edelbrock Performer 2.0 intake manifold (dual-plane).

    Installed new Atomic system a couple of months ago and so far it's been running great. No codes are showing. Although I haven't had it out very much, due to bad weather, I have noticed a slight surging happening at cruising speed. My question relates to the intake manifold. I'm led to believe that "notching" the plenum divider of the manifold could help alleviate with this surging. Yes/no? Is it worth doing? Note: I can't use a spacer because of tight hood clearance.

  2. #2
    Join Date
    Dec 2009


    Quote Originally Posted by Kim72 View Post
    Note: I can't use a spacer because of tight hood clearance.
    Then you're taking a risk without testing the theory with an open spacer. Maybe remove the hood for testing, but if it ran fine with a carburetor (& same intake manifold), then it should run fine with TBI. Meaning it could be a tuning issue.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3


    Thanks for the reply. Yes, you're definitely right, I'd be taking a chance if I went ahead and cut a notch. I'm hoping to hear from anyone who has experience with this. I plan on seeing if the system will Learn itself some more when I can get some good cruising miles on it. Until then, I don't plan on doing anything rash. Just considering it.

  4. #4


    UPDATE: To refresh, I was having surging and some cylinder missing issues from about 1500 to 3000 RPM. This would mostly happen in 1st gear, but also cruising, in traffic, at those RPM. Was driving me crazy! So I bought a 1" carb spacer to see if bypassing the intake manifold plenum divider would solve my problems. Nothing else I tried seemed to work. Well to my surprise it made one heck of a difference. Those issues are now gone. I'm smiling again! I did end up notching my plenum divider as it's in a Corvette with very limited hood clearance. I notched it only 1/2", but that worked great also. So if you're having some of the same issues, I'd highly recommend buying a carb spacer, if you have the hood clearance, and giving it a try. It worked for me!

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