We rebuilt the top end of this 302. It's run fine for about a year. All of a sudden, lately it just seems to be hit or miss. It may run ok for a while, but then it seems to to get choked, misfire, and eventually kind of load up and die. Fuel coming from the pump has good pressure when I crank the engine, I tried a different carburetor, that didn't help. Does anyone have any suggestions?
I cant tell you exactly, but I can tell you from using over 10 different 302s in off topic cars, they are very finicky in just the way youre describing. My daily truck has a fuel injected 302 and still idles strange and sometimes wants to die. I did a full tune up last month and ran seafoam through the fuel and straight into the intake and it really helped it, had a lot of carbon build up, maybe try that, otherwise, sorry I cant be anymore useful. Are you maybe running TOO MUCH fuel pressure?
That's a thought. Because it does seem like it loads up a bit before it dies. Thanks for the input, I'll look into that. I've had a couple of different 289's for years and never had problems like this one. Those motor's are fairly close.
Check your carb floats, maybe she's leaking through, You could have a bad lifter thats loading up, you could have pulled up one of the rocker studs, you may have junk in your gas, you may have a plugged fuel filter, may need a set of wires. Could be a short in the ignition system.
I'd pull each spark plug wire, one-at-a-time, and inspect it. They just don't seem to last like they used too. Free, and easy too.
One of my favorite troubleshooting tools is a vacuum gauge. It's effective AND cheap. Check out this site for the basics: http://www.earlycuda.org/tech/vacuum2.htm
Thanks for all these great suggestions guys. The fact that the problem is intermittent is what stumps me. It only does it when it feels like it. Sometimes it runs great. Anyways, I have a number of places to start looking now. Thanks again.
Run a vacuum hose into the car, then have a look at the gauge when it does finally act up. I did that for a customers car once. He had a strange noise that only happened when you had driven for about 20 mins of highway, then pulled up to a traffic light. It made a hell of a racket and the car lost all power and the idle dropped tot about 200-300 RPM. He had had the auto trans rebuilt, pulled out 2 more times, a new alternator, water pump, etc,etc. None of the local mechanics could figure it out. He spent $2500 before he called me. I did the remove belts one at a time routine, AC, then power steering, then water pump, etc. No change in the symptoms. So I hooked up my vacuum gauge and rode around until the noise occurred. Bingo! vacuum dropped from a 19(Steady) down to about 4(rough). I had suspected a vacuum leak on the intake manifold, which I confirmed with a can of WD40(blew it around the gasket until it sealed for a moment). Final diagnosis: loose intake manifold stud. 3/4 of a turn on it, problem cured. the gasket was buzzing like a reed in a clarinet. 1.5 hrs of diagnosis and 40 seconds wrench time. Boy, was he pissed at the time and money he had wasted with the other guys.
That's a great story. I always have my vacuum gauge with me. It's one of the best tools I have. If the problem isn't obvious or visible...out comes the vacuum gauge. I always recommend a dash-mounted vacuum gauge, but the recommendation it's often ignored due to ignorance.
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