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7/7/10 8:04am - Original Message: 'flat spot'
manchestershark Lifetime Member
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Equinunk, PA - USA

1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.

Joined: 10/31/2007
Posts: 1942
 Go easy on me now!  I have a old, rebuilt recently Rochester Carb. It seems to perform great after It comes off the initial opening of primaries. At idol, starting out in first gear, or after a slow down in any gear. The beginning of the throttle opening has a slight flat spot or hesitation. Am I to lean on air screws or is there a internal problem with carb? After it begins to accelerate, 12-1500 RPM it runs GREAT. Secondaries SLAM in and is seemless in performance. Do I live with it or try to remedy the flaw?  THANKS for the input.  CARLISLE is comming so I need to make a decision so I can look for something else if need be, new or used.  I am aware of the qualities of EDELBROCK, but would like to stay with OEM for gas economy and the originality.  Mark
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7/7/10 9:21am - Reply: 'flat spot'
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1974 coupe. 350 CID with Turbo 400 trans. Decal says 8.5:1 compression. Needs paint and AC replaced but don't plan on full restoration. Car runs strong. No big problems so far. 67,000 miles on Odometer, probably rolled over

Joined: 7/3/2010
Posts: 65
It's been a long time since I worked on an old Carb but I do recall back in the day this was sometimes  caused by the accelerator pump. There was a little leather type cup it there and if it failed you'd get a flat spot on initial acceleration. That pump gives a little squirt of gas at intitial acceleration. If it doesn't you gat a lag, or flat spot. I don't know how to describe it but it will be on top of the carb probably on the bowl section. It's possible the bowl isn't filling all the way due to a stuck float.
This all from memory. Like I said it's been a long time.
But before I'd do anything drastic I'd check the Idle adjustment. Idle adjustment might also cause it and so can a faulty advance mechanism
BillinNashville2010-07-07 06:42:54

It has been over a year since I started. I had to quit the project so the car just sat in the garage. I was able to get started again in May 2012. As of July 27 2012 I have done the fiberglass repairs and applied Slick Sand High Build Primer.

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7/8/10 12:14pm - Reply: 'flat spot'
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Mounds View, MN - USA

70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe

Joined: 5/24/2007
Posts: 1031
I agree.  I would also suspect the accelerator pump linkage.  Sometimes there are two holes to choose from, and there are adjustments on the rod.


Corvette Specialties is your best source for Corvette parts, accessories and gifts. www.CorvetteSpecialties.com


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 Forums -> C3 Fuel, Emission Control, and Exhaust Systems
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