engine problems???? HELP!
 

I spent nearly an hour on the phone with my son in NC last night trying to get his 70 K-10 straightened out. The truck has a 350 with new HEI dist., new edelbrock 600 with manual choke. The engine starts and idels perfect, but when he gives it throttle it sputters and back fires. He checked all the usual things like vacuum leaks, timing, even installed a new fuel pump. Still does the same thing. The truck ran perfect last week when he drove it to Pigeon Forge. Anybody got any suggestions?

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71 C-10
72 K-10 4WD
72 Suburban
Oceana, West Virginia

Sounds like a distibutor or timing problem. Did he put the new hei in since last week? I would check timing.

If it starts right up, I was thinking carburetor problem. Turn both of the front screws in all the way, then back out a turn and a half. then check to make sure that all of the vacuum sources are either hooked up or plugged.

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Yeah, that's right. My name is Randy too!
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1970 Chevy C-10 shortstep
30 Ford Model A Coupe 4 inch chop, 350, GMC 671 blower-Hell yeah it's fast!
87 Harley Sportster(couldnt get a 350 to fit)
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Virginia Beach, VA.

Did he change the carb or distributor (or anything else) since the truck ran right?

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Tim

Also check for plug wire mis-location....I have seen this do this.

A few possibilities come to mind

Easiest and most probable:
Unplug your vacuum advance. The wires on the pick-up coil to the ignition module are very thin, very brittle(with age) and move back and forth constantly. I've seen this before in the shop... Idles good but when the throttle is moved, vacuum starts to apply the vacuum advance circuit and the wires loose contact.


Leaning out: If the power circuit in the carburator is plugged with debris you will have perfect idle quality but a terrible hesitation/backfire (this usually happens to either the left or right booster) IF this is the case.. IF! there is an old trick which will pull the debris on through. This whole procedure needs to be done very quickly. Put one hand on the throttle linkage and one hand on the choke air valve. While opening the throttle to near full throttle, quickly close the choke air valve(plate) until it almost dies then release the choke. Repeat this 2 or 3 times until it clears out. Please be careful doing this trick, keep your head out of the way in case of a backfire.


Another possibility

Weak ignition coil: If the coil is weak, only producing 5-10kv(hei), you will have decent idle quality but the coil will break down when more voltage is needed. The bad part about this coil is when its going bad... It acts almost identical to a lean condition. Tough to tell the difference at times.



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'71 LWB
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Garrett
Olathe, Kansas

Thanks for all the suggestions. I havn't talked to him today yet (he's supposed to call me during his lunch break) I printed out all the replies so I can pass them on to him. Thanks again, Larry Bailey.

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71 C-10
72 K-10 4WD
72 Suburban
Oceana, West Virginia