i have an 87 camaro with a carbed 305, stock carb but with an edelbrock performer egr intake, edelbrock tes headers, and flowmaster catback exhaust, also msd 6al box and blaster 2 coil. it runs good under regular acceleration until about 3500-4000rpm, then it starts to cut out and stumble. If i give it full throttle from a stop it will accelerate good for about 3 seconds then drastically cut out at 4000. The whole fuel system is stock, so i think it may be the pump, the carb, or possibly th o2 sensor, any ideas?

 

Welcome aboard.

Could be fuel delivery - the fuel filter in the carb, or one of the fuel pumps.

The O2 sensor doesn't do anything at wide open throttle, so that probably isn't it.

Ignition is the #1 cause of carburetor problems. But, you seem to have that covered (you don't happen to have a 4000 RPM rev limiter, do you?). Assuming the cap, rotor, wires, and plugs are up to snuff.

 

i replaced the filter and ive checked the whole ignition system many times, and i have the 6000 rpm chip in the msd box. ive heard that the stock fuel pump may not be strong enough for any modifications, is that true? if so what would a good replacement be?

 

I put the fuel pump off my old 305 on the 355 (intake, headers, catback, carb, cam) when I put it in and it pumps fuel to the new engine just fine. I prolly should change it sometime...who knows how old it is. If I were you, I'd find a way to bypass the MSD setup and run the distributor just like a stock HEI would be used (providing the fuel pump is good).

 

Fuel delivery is usally load or power related. Since you seem to be having problems at a specific RPM, that doesn't lend itself to a fuel delivery problem.

(FWIW, the '87 LG4's have both an in-tank electric and engine-mounted mechanical - both have to be working properly. The factory put an in-tank electric and reg in the ZZ4 kit.)