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Old 09-30-2019, 02:15 AM
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DeeVeeEight DeeVeeEight is offline
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Default Stumble @ Cruise

I have a fresh 355 with a mild build (355 hp, 390 tq.) roller cam, 9 to 1 compression, air gap intake manifold topped with a Holley 4150. Vacuum is at 16 inches, idle @ 750 rpm. Idle is great and the engine runs strong and smooth.
When cruising on the highway, if I accelerate lightly there is a bit of a stumble. I have been doing a bunch of internet reading but this is where I come for the answers I trust. I am leaning towards the primary jets being too lean. At first I found that the accelerator pump was out of adjustment and I have that back within specs (as far as I can tell) and it has helped a lot - but the stumble, though less noticeable is still there. Your thoughts as always, are appreciated.
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Old 10-06-2019, 11:04 AM
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BBShark BBShark is offline
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Have you looked in the carb to see if you are getting a jet of fuel?
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Old 10-07-2019, 02:15 PM
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I agree with the previous post about first checking the operation of the accelerator pump.

Also, do you have the appropriate accelerator pump cam for your carb/manifold combination? A pump cam swap a few years ago cured the tip-in stumble on my engine.

My $.02
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