C3 Boggs when under load

**David M.** · May 11, 2006, 10:54 PM

Re: C3 Boggs when under load

Is it a Quadra-Jet? If so first pull out the filter in the inlet. Change it. But first grab that rubber end on the filter and rip it out and throw it and the plastic thingy as far as you can. That filter prob. caused me quite a bit of hair loss. Car ran out of gas at higher rpms under load. There is an adjustment on the secondary air valve(butter fly). Back pass side of carb. Allen is up-side down. Its accomplished with a allen and a screw driver. Loosen the allen be sure to hold the spring loaded rod with the slot that your screw driver is in or you'll loose the tention and then you wont know where you were. Try tightening it 1/8 of a turn, than road test. If better than your going in the right dir. Try tightening it another 1/8,(1/4 total from orig). If that doesnt work loosen it to the starting point(1/4 back to orig pos). Now try 1/8 loose. I'll bet the tight direction works for you. Let us know. Course if its not a Q-jet I wasted band space.

**David M.** · May 11, 2006, 11:06 PM

Re: C3 Boggs when under load

If its a late C-3,81ish with the E4ME/C microprocessor controlled Q-jet let me know cuz theres a couple of things/adjustments that are unique to that animal. There's specifics to get it to run good during heavy to WOT acceleration. It has electronic parts in it that coinside with the OBC/ECM. Let me know.

**Clem Z.** · May 12, 2006, 05:51 AM

careful about removing filter check valve

if you remove the filter check valve and the carb has a "windowed" needle seat and the fuel pump has a return line to the tank the float bowl will drain down and make for hard starting. the "window" is below the fuel level and with no filter check valve to hold back the fuel the level in the bowl will drop. most after market carb kits do not come with "windowed" needle seats so the fuel has a hard time getting past the needle at wide open throttle so i cut windows in these needle seats when i use them to get max fuel flow at WOT. this is a "must" on BB corvette engines

**Dave Jarosz** · May 12, 2006, 10:46 AM

Re: C3 Boggs when under load

Dave, Its a Q-jet on a `76 C3.

**Bryan L.** · May 12, 2006, 10:58 AM

Re: C3 Boggs when under load

Check and see if the return line from the pump to the tank is plugged. This will make one run like crap similar to a fuel starvation problem.

BL

**David M.** · May 12, 2006, 04:40 PM

Re: careful about removing filter check valve

Good point Clem. I dont have the start problem but My BB sure did run outa breath at WOT. Hunted it down forever. Pulled the check valve and walah runs like a rap*d ape now. I have seen in line style check valves that flow more than that filter valve does so thats another way around it if it causes starting probs. FYI stay away from the sintered-bronze (morraine) filters they do not flow at all especially after some use. The horn filter can be eliminated altoghther by installing an in-line aftermarket filter between the pump and carb.
Dave, try adjusting the secondary air valve as I mentioned first(no disassembly involved) Then I'd verify fuel PSI 5-6psi. Next is the float any good? Does it float or sink. Check its level and drop specs. While your in the bowl area verify the power piston isnt sticking. If it is pull it and crocus cloth the shaft (1200grit and up sand paper will do too)so it works freely. Verify the spring under it is ok. Theres other things to check but its gets complicated. If your inclined I recommend getting Rochester Carburetors by Doug Roe. Fine piece of literature. Helped me 100 time over in the past 20 or so years its been published.

**Clem Z.** · May 14, 2006, 05:53 PM

i would guess you had a bad check valve

because GM did not send them out from the factory with this problem.

C3 Boggs when under load

C3 Boggs when under load

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