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Old 07-02-2014, 09:50 PM   #1
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Well I thought we had it figured out guy`s

My 88` Yj was running great after my last Thread. BUT I was wrong. It ran great after the carb gasket replacement for about 100 miles. Now its backfiring again. I have the GM HEI to swap out could this be the problem? If so is their anything I need to change on the HEI to make it work? I have been going round and round with this for almost a year now. Any help would be appreciated.

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Old 07-03-2014, 08:28 PM   #2
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More info on your setup would be of help. I'll assume you have the 4.2L. Which carb do you have? Any other engine modifications besides the GM HEI?

Backfiring through exhaust usually indicates either timing too retarded, or engine running rich, or possibly other valve/timing problems.

Backfiring through the intake indicates timing too advanced, or engine running lean, or possibly other valve/timing problems.

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Old 07-04-2014, 07:03 AM   #3
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Sorry, Just frustrated. It`s an 88` With a 78`4.2l 80k on engine. Has been nuttered , MC 21XX (new). Going to put in the HEI this morning. That's it for upgrades until I get it running right. Then the fun begins.
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Old 07-04-2014, 09:18 AM   #4
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Quote:
Originally Posted by Harmbl View Post
Sorry, Just frustrated. It`s an 88` With a 78`4.2l 80k on engine. Has been nuttered , MC 21XX (new). Going to put in the HEI this morning. That's it for upgrades until I get it running right. Then the fun begins.
Sounds like timing is off to me. Thrown on that hei distributor and get the timing adjusted. Also gap the plugs at .045 with the hei. Hell plugs are cheap enough to but some new champion coppers iirc they are #82's. And get some 8mm wires for a 83 f150 with 4.9l i6
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Old 07-07-2014, 07:08 PM   #5
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Dizzy`s in, Already had the 8mm wires need to do the plugs ( wasn't sure of the gap) Running good now but always room for a little improvement. I appreciate all the help I have gotten for everyone on this site.
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