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Old December 4th, 2005, 08:34 AM   #1
Icemanii
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Default CJ still knockin on acceleration

What I have:
"83 CJ7 with a 401, Holly bbl, Headers, and an automatic

What it does:
Spark knocks a lot on acceleration, nothing at idle

What I have done:
Had it timed and tuned at the corner station. He adjusted the carb, timing, changed the plugs, and the rotor.

What now? Need help on this as I need this running for the winter. Thanks for the serious replies. Any suggestions or offers of help will be great.

RJ
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Old December 4th, 2005, 01:59 PM   #2
Yetti
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Well the first thing to try would be a better grade of fuel. it could be just that easy. secondly I would back the timeing off at 2 degree incriments till it quits. I don't know what has been done but if its moded then you have to account for everything done to this point.
by the way what distributor do you have in it?
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Old December 4th, 2005, 03:23 PM   #3
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CJ has a DUI ignition system in it. Wires are good, cap, and coil are also. Will try the different fuel, and backing it off 2 degrees. I think it is at 8 BTDC, so you think 10 BFTC or are you saying 6?

Thanks for your help.

RJ
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Old December 5th, 2005, 03:38 PM   #4
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Retard the timming, so try 6*BTDC. Also, do you have a functionable EGR system? That will drastically help detonation, it allows innert gas to inter the intake, and so will allow a cooler combustion helping with detonation. If you took the egr off, you may want to try that, or spend the money on a high octane gas and see if that helps. With a 401, what carb are you running? You say it is only detonating on acelaration, is the secondaries not big enough? Does it ping on a continuous load (ie, crusing on highway), does it have a lean surge? Is this motor bored? Pistons? What is your compression, what heads do you have on this thing (different years had different compression). If we can't help you here, then try www.bulltear.com forums.
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Old December 5th, 2005, 04:21 PM   #5
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I think it might have too much timming swing. if its set to 8btc it sould have a max of 31 after that. total swing shouldn't be more then 37* total. if you can get a timing light that allows you to read the max advance you can see how far from this yours is at. if you have to back it off till you reach the total max advance.
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Old December 5th, 2005, 04:24 PM   #6
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Quote:
Originally Posted by Yetti
I think it might have too much timming swing. if its set to 8btc it sould have a max of 31 after that. total swing shouldn't be more then 37* total. if you can get a timing light that allows you to read the max advance you can see how far from this yours is at. if you have to back it off till you reach the total max advance.

That may be the unknown with a DUI Dissy, It is pretty much a GM HEI unit, not sure if they recurve teh mech an vac advance for the AMC's, especially the 401.
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Old December 5th, 2005, 06:36 PM   #7
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thats what I was wondering Shawn. I figured someone did a "dropin" and expected it to work right out of the box.
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Old December 7th, 2005, 01:28 AM   #8
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I know there are articles on timing AMC V8's at the AMX Files site.
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