Fuel Delimma

I have a 67 Mustang Coupe. Rebuilt 302 (from 68 model).

I've had problems with rough running with my new engine. The problems are similar to problems I had with me last engine. I think it is a vacuum leak, but I cannot find one anywhere. I have replaced my gas tank because I saw some (minor) rust in there. replaced my fuel pump and pump to carb line. Replaced all rubber sections of main line. Replaced entire ignition system, and went to electronic (Pertronix) ignition. Have a new PonyCarbs Autolite

2100 which should be solid. The only things on this car which are from the previous installation are the intak manifold, the exhaust pipes (which are soon to be replaced), and the main fuel line (pump to tank) which has been blown out with compressed air.

If not a vacuum leak, then does anybody think there could be a problem with the fact that the 68 302 fuel pump has a 3/8" inlet for the main line, but the main line on a 67 is 5/16"?? Should not be a problem, right? I just have a 3/8" fuel hose clamped down tight on the 5/16 line, and that's ok, right?

Reply to
Jef Gearhart
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Is it rough idle or rough across the rpm band?

Reply to
Larry Hepinstall

The carb came from Pony Carbs in New York.. It refurbished. They came highly recommended. Further, I have rebuilt two other carburetors (same model) prior to buying this one. Confident I did it correctly, and had same results..

What is sort of weird, in my hours upon hours of fiddling with the mixture on those carbs that I rebuilt, it always seemed like one bank was timed differently than the other, if that makes any sense. That is what finally lead me to believe I had larger problems, and have the engine rebuilt.. I am beginning to think that maybe the long shot suggestion that my exhaust pipe may have some blockage may be correct. They sure are old. What do you think?

Thanks for the input.

Reply to
Jef Gearhart

Should not be a problem. If you really wind that 302 out, you might run out of fuel with the 5/16" line. As long as it doesn't leak, that's not your problem. As to rough running, could be a plethora of small problems. Vacume leaks are common, so be sure to eliminate that possibility before going further. You'll need to whittle the list down with some other info: hot or cold? Idle, mid range, upper range? Plug conditions? cam specs? under a load or not? The ignition system is a common culpret, and the fuel system is rarely the culpret. So inspect the entire ignition system carefully. Go over the Pertronix instructions again to make sure everything is correct. Be sure to bench test the coil and distributer. Sometimes its something as simple as a pinched wire, or a dirty cap tower. If all that looks good, make sure you have good compression in all cylinders. Even on a new engine, do a compression and leak down test. If all that comes out OK, then start checking the fuel system. Who knows, maybe the carb was assembled wrong, or has some dirt in it.

Reply to
.boB

Thats worth checking out since its just about the only thing you haven't done.

When you rebuilt it, did you use a modern cam or one with the old firing order? The newer cams use the 351 firing order instead of the old 289 firing order. If you have a new cam, move your plug wires to this firing order

1-3-7-2-6-5-4-8.

LJH

95GT

Reply to
Larry Hepinstall

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