I recently built a 400+hp 302 for my 72 Comet. It was running great for about 300 miles, then it started spitting & sputtering. It actually stalled on me a couple of times. I had a friend take a look at it and he got it running again. But, if I keep it at a steady RPM it does the same thing, though it doesnt stall now. The wierd thing to me is, I can let off it and it stops for the most part. You can hear it resonate through the exhasut. Or I can give it more gas and it stops. Or, if I stomp on it off the line (not drag raceing but in general), it gets to about 50mph and spitts & sputters. If I keep on it; It keeps doing it or I can let off and it does the same thing, resonate through the exhaust. I do have electric ignition with a 600 cfm 4V Performance carb. I think maybe it could be getting too much gas or not enough? I changed my coil and it still does it. I looked at my #1 plug and it doesnt look that bad. Im running AutoLite 45's. Is that not hot enough? It is a 11:1 compression motor. Anyone have similar problems? Im open to any ideas. BTW: EVERYTHING ON THIS MOTOR IS BRAND NEW!!!!
Could also be a lean condition as well. Or an ignition problem. You DO have a fuel filter somewhere between the tank and carb don't you? A plugged filter will do this as well. Or water in the fuel. I see you're in Arizona, so you can add vapor lock to the mix too. Especially if you still have "winter gas" in the tank. This blend builds more vapor pressure than summer gas.
lean miss, ran into the same thing with mine, among other problems, same carb, get the jet and rod kit for that carb, I stepped mine up 2 stages I think to get rid of the mid drivability miss, also try adjusting the accelerator pump lever
If it was "running great for 300 miles", how would it suddenly become 'lean' and need bigger jets?....
The car did sit for more than a year before I got this new motor in. I have two filters; One pre-pump and one clear pre-carb. The clear one doesnt look too cloged up. Ill change the pre-pump and see if that helps. It didnt have that much gas that sat though. Not even an 1/10 of a tank. I dont know how it ran for 300 miles great and suddenly had problems. Thats the story of this car though. EVERY step of the way, it has always been something. Ever since i got it running, it has ran rich. Ive heard that edlebroke carbs ALL WAYS HAVE PROBLEMS RIGHT OUT OF THE BOX.
Exactly........... That's how I know when it's time to change the inline filter between the tank and pump on my Ranger. It develops a high rpm miss when the fuel bowls run dry.
Is there black smoke coming from the pipes, or soot? I know from experience with my Holleys, that after sitting for a year (or more), the needle & seat assemblies have gotten gunked-up and not closed all the way, causing it to dump fuel at idle and run like crap (rich)...
Sounds like a bad power valve to me. Leaking through the diaphram, but not getting proper fuel at accelleration. I had the same problem, and replacing the power valve solved it for me. While the fuel bowl is off, check the needle and seat, and for dirt, etc. Good luck!
None of these parts sat for a year. The car did. All the parts for this NEW motor are brand NEW; From the carb to the mains, to the vac lines and clamps. It blows smoke but I think its form the rings not seating all the way yet. Plus, the pipe my friend used for the exhaust was dipped in some rust preventive junk and I think that causes some smoke too. Ohh and it doesnt do it only at high rpm, it does it if I keep it steady at any rpm.
