As my username implies, my 87 4bbl carbureted Trans Am is purring with a used truck engine under the hood, and it runs fine, but I floor it, it smoothly accelerates to the redline in first, shifts, then hits the redline in second at around 60mph and then the needle either drops to 1000rpm or the car begins to surge as if I'm pumping the gas pedal. What gives? Is there some sort of rev limitter choking my bigger engine? Is it my carb? Fuel pump? Any ideas on how to fix this would be greatly appreciated as I'm eager to take it to the track but can't due to this very annoying problem.

 

In your case, it sounds like the rev limiter is called "fuel supply".

You either have a plugged fuel filter or a weak fuel pump. You may even have two fuel pumps - an electric in the tank, and a mechanical on the engine. If either is weak, it'll cause the problem you describe.

As far a choking, if you have the stock air cleaner, exhaust manifolds, y-pipe, cat, and/or catback, you ARE choking it! However, that wouldn't cause your surging/RPM loss. In fact, fixing those choke points may in fact make the problem worse until you fix your fuel supply problem.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4, 2300 stall TC. Ported World 305 heads, Crane PowerMax 2050 cam. ZZ3/4 intake, oil pump, pan & baffle. Accel HEI SuperCoil & module. Hooker 2055 headers, 3" Catco cat & 3" catback w/dual-opposite Flowmaster 80. 2.93 limited slip. Spohn SFCs waiting to be installed. AMSOIL syn lubes bumper-to-bumper. Daily year-round driver. Best ET, speed TBD...
57 Bel Air, my 1st car. '66 396, 9.7:1 forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 700 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

Thanks, man, for confirming my suspicion. Seeing as how this was originally a carbed car, I don't think there's a pump in the tank, but there is an electric one in the engine bay which may be the el cheapo $30 Pep Boys rig from when the previous owner did the swap. I think I'm gonna yank it and throw on a Carter mechanical 6psi 120gph pump for $51 from Summit. So that oughta do the trick, eh? Great! Next up is SLP headers and y-pipe, a Catco 3" cat, and a Flowmaster catback! Thanks for the help!

 

You may very well have an electric pump in the tank, from the factory. The CHP "My Generation Camaro", '87 model, had one, as well as a mechanical on the engine. If yours has that in-tank pump, and it isn't working, it could be causing a restriction that the other pump can't overcome (and the Carter couldn't, either).

"Swap"? What was swapped if you have a carb now and it was originally a carbed car? Was it converted from CC carb to mechanical? If so, was the distributor changed out to a vacuum/mechanical advance type? If not, that could be your problem, or at least part of it.

Still sounds like fuel starvation, though.

 

maybe you just need a tune-up. i had a similar problem with the bogging. there was a LOT of carbon buildup on the sparkplugs and the rotor in the distributor had seen better days. still had a minor bog after that, but after the timing got bumped up a few degrees it ran just fine.