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Peggy Sue
04-27-2013, 03:38 PM
My '57 Chevy Bel Air Sport Coupe has a bad hesitation problem upon acceleration from a stand still or very slow speed. Car has a stock 283 CID V8 engine with a Rochester 4-bbl carb. I've fiddled and fiddled with the accelerator pump (installed new parts adjusted and adjusted) and it still does it. I have the same problem with my '55 Chevy Bel Air Convertible with a stock 265 CID engine with a Rochester 2bbl carb, but to a much less severe degree and it tends to go away after a little driving of that car. A car buddy said I should try to find the old style leather accelerator pump diaphragm. The new kits come with a vinyl (rubber?) material. I would appreciate any constructive comments on how to eliminate this problem and/or where to locate the old style accelerator pump diaphragm. Thx

Maddog
04-27-2013, 04:01 PM
Your description sounds like an accelerator pump issue, the check is to see if it has a healthy squirt as soon as the lever is pushed slightly, if it does then it's not the acc pump. If it pases the squirt test then make certain your initial timing is at least 6-8 degrees, no more then 10-12, lack of initial timing can give a hesitation.
I think your accelerator pump is weak, the newer rubber type are fine make certain the bore is not pitted which would render a new pump ineffective.

chevynut
04-27-2013, 05:37 PM
This really belongs in another forum, not in "support and feedback" which is supposed to be for site navigation and tools.

But anyhow, if you've rebuilt the accelerator pump perhaps it's related to timing, not the carbs. I would just junk the carbs and go EFI. :)

56-210Sedan
04-28-2013, 06:37 AM
If your acc pump checks out then check your idle air mixture screws and also check make sure you have no vacuum leaks, and rare make sure your intake is good and has no cracks or pin holes. Out of curiosity how did these carbs work before rebuild what is your reason for having it done or was this something you bought rebuilt?

Peggy Sue
04-28-2013, 12:13 PM
Both cars had this problem when I acquired them.

warren57
06-25-2013, 07:42 PM
This really belongs in another forum, not in "support and feedback" which is supposed to be for site navigation and tools.

But anyhow, if you've rebuilt the accelerator pump perhaps it's related to timing, not the carbs. I would just junk the carbs and go EFI. :)




What post are we in, I'm lost. I thought we were in "fuel injection...."? :)
But you're right EFI sure works better. Are any of the after market EFI units that bolts to the carb manifold any good? (Holley, MSD, Powerjection, Edelbrock) Very pricey...