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Old 08-29-2003, 05:32 PM
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Poorly running 327 question

Please take the time to read this and offer any comments you may have. Thanks.

My 327sbc engine runs fine for about 5 minutes and then begins to run rough and has no pwer. It pulls about 17 to 20" of vaccum for about 5 minutes then starts to fluxtuate then drops down to about 7". If I wait about 10 minutes the symptoms are very repeatable. When it is at 17 to 20" it idles and and sounds great. I've had a timing light on it when it changed and the timing did not change one bit. I tried timing it at 8 and 12 deg BTDC with no change. When I look at the spark at all of the cylinders I see a nice blue/white spark (not yellow or red at all). I tightend down the intake manifold bolds but they were already snug. I held a propane torch (not lit of coarse) around the intake and carb looking for vaccum leaks and found nothing. I pinched off the power brake and transmission modular valve hose and there was no improvment. The fuel is at about 6psi on the carb and if I give the throttle the slightest tap I see fuel squirt into the carb. One wierd thing was that when the vaccum was low I tried adjusting the idle speed screw on the carb and didn't realy get any increase in engine speed. It did rev faster the next time I started the engine and the vaccum was high but the speed dropped back down when the vaccum dropped again.

I'm using a new coil, rebuilt stock HEI distributor, a brand new Edelbrock 1406 carb, and the whole engines been recently rebuilt. It ran great for a long time and this is a new problem.

Is this a carb issue? Why does it work fine after I let it sit for 5 minutes? I dont think its a heat problem beacause the car isn't cooling don in that short of time. The timing isn't drifting. Could I have a stuck float seat in the carb?

I dont know which way to go now. Please guys...help a fella out.

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Old 08-29-2003, 07:07 PM
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although I`m not sure this is your problem, but it is something to check. my car used to do this exact same thing, and it was the fuel pressure, after it would run 10 minutes, gas would flood out of the boosters, it would sometimes keep running, only real rough. remove your air cleaner and get a flashlight, run your car at idle and when it goes to acting weird, shine the flashlight in the carbs throat, if you see fuel pouring out, you found the problem.
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Old 08-30-2003, 04:45 PM
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Thanks a ton for that advise. I didn't see the fuel you were speaking of until I lightly tapped the carb with a hammer. Then the thing started belching fuel. I tore down the carb and found a little debris in the float bowls. I cleaned out all of the orifices, reset the float levels; which by the way, were way off on this brand new carb. I threw it back together and it ran great! I took it out for a cruise and flogged the !@#$ out of it and she runs like a top again.

I guess the fuel would eventually get to a level were the engine began to flood. After it set for a few minutes the excess fuel evaporated and then it would run OK for a while.

Thanks again double vision.
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Old 08-30-2003, 10:57 PM
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No problem 54, I like to help anyone when I can, as do many others on this site that know far more than I ever will. but when I had these problems with mine, I fought them alone for a long time, but I learned a whole lot from it, and if I can take something i`ve learned and help someone else solve there problem, it makes my day.
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Old 09-01-2003, 11:58 AM
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i had this same prob awhile back and after going through 3 carbs i found out the fuel pump i was using had a return line which i plugged off..i've done this many times in the past but for some reason this time it was pumping to much pressure..after a new pump i was running again
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