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Old 09-15-2003, 02:17 AM
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Ignition or fuel? - SBC cutting out

Please help!! I'm running a 350 Chevy in my 32 sedan (only 2000 miles since I built it) with a Mallory Unilite electronic distributor and the correct Mallory coil and ballast resister. Also using a new Holley manual fuel pump & Edelbrock carb. I wired it with a Ron Francis kit.

The set up has been working fine all summer but this weekend has been cutting out after after a period on the road (40 miles?) sometimes after sitting in traffic, - it starts missing while cruising and cuts out under load, not firing on all 8. Had to pull over a few times cos it finally dies, and the ballast resister is red hot, & coil is pretty warm.

After a few minutes it fires again but on a trip yesterday it would only get me another 2 miles. I don't think its fuel as you can slip it into neutral and it will rev again, popping & banging as the unburnt fuel is lit - though I guess it could be vapourisation of fuel??

I swapped in another ballast resister last night and as soon as the ignition is turned on it gets too hot to touch within seconds - seems to suggest an ignition problem? - though not sure if they always do this?

Does anyone have any ideas, before I start replacing parts in desperation? Many thanks, Limey

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Old 09-15-2003, 03:58 AM
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The ballast resistor will get hot during normal operation. It shouldn't get hot enough to melt the wire or anything though.Overheating of the ballast resistor is usually caused by an over-voltage condition.

The coil will also heat up, but usually not too hot to the touch.

I would run some tests on the ignition system before I started replacing parts.Most tests are simple and require nothing more than a multi-meter.

I am not that savvy with ignition systems and I am not at all familiar with your distributer, but I am sure someone more knowledgeable will be around shortly.
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Old 09-15-2003, 05:38 AM
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Arrow

I know several people that use the unilite and like it ,but others that have had problems. I'd put a known good points distributor in and see if that improves it. That will help in tracing down the culprit. You might also re-check the wiring to the ignition. It will probably be a process of elimination.
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Old 09-15-2003, 07:35 AM
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It could be a water buildup in the carb float bowls ot filter. The more you drive it the worse it gets, and after setting its OK them get going and soon it sputters again. Sounds like a fuel problem.
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Old 09-17-2003, 08:12 AM
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Few things to look at thanks guys. Anbody got any thoughts that might help me diagnose....?

Cheers, Limey
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Old 09-17-2003, 08:25 AM
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What type of fuel pump from Holly, maybe to much pressure for the carb. Eldelbrocks like 4 to5 lbs. pressure after that they like to flood. The better Holly makes 7 to 9 psi.
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Old 09-17-2003, 08:36 AM
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I'm running one of those chrome ones with a base that you can undo and rotate. Could be over-fuelling I guess, though I'm not sure that would cause loss of power & cutting out??

Any other thoughts anyone? Thanks
Limey
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Old 09-17-2003, 08:53 AM
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sounds like your cam has gone flat and your valves aren't opening fully so it makes a popping sound

did you check your firing order

21843657

also maybe thecoil has gone bad, maybe a wire is off somwherre
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Old 09-17-2003, 08:56 AM
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Why are you running a ballast resister? Those were used in the "old days" with points to allow more voltage during startup. I'm running Mallory unilite with MSD 6a and Blaster II coil without a ballast and runs great. Unless I'm missing something here, dump the ballast.

-Brad
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Old 09-17-2003, 08:59 AM
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I'm using ballast resister cos' the instructions from Mallory for the distributor and coil told me to!!
By the way what's an MSD 6a ?
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Old 09-17-2003, 09:24 AM
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Quote:
Originally posted by Limey Simon
I'm using ballast resister cos' the instructions from Mallory for the distributor and coil told me to!!
By the way what's an MSD 6a ?
Really? I'm surprised that Mallory would require a ballast. Maybe just try bypassing to see if the problem disappears.


MSD is a capacitive discharge ignition with multiple spark. I could really tell the difference when I added it. Very popular product.

Check it:

http://www.msdignition.com/
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Old 09-17-2003, 09:53 AM
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Don't bypass the ballast resistor.
Mallory requires it for a reason.

Here is a good site for troubleshooting and testing your system.

http://www.centuryperformance.com/mallory/index.asp

Last edited by drlindz; 09-17-2003 at 10:00 AM.
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Old 09-17-2003, 10:05 AM
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Quote:
Originally posted by drlindz
Don't bypass the ballast resistor.
Mallory requires it for a reason.

Here is a good site for troubleshooting and testing your system.

http://www.centuryperformance.com/mallory/index.asp
It wouldn't hurt anything to bypass the ballast for a 5 minute test.
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Old 09-17-2003, 10:17 AM
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The reason for the resistor is for keeping a constant voltage at 10 volts, it is because the amount varies with demands and keeps the distributor constant.
DO NOT RUN WITHOUT IT.
I have run a Mallory Comp 9000 for 10 years with a Hyfire4 CD and street coil without any problem.
I did with an MSD before that.
The regular Holly fuel pump goes from 6 to 8 psi.
I think its to much pressure for the carb causing it to run rich and load up the plugs over the summer giving you the problems that you have now.
Check your fuel level, and spark plugs for color, could be starting to gas foul.
The ballast resistor will get hot during normal operation thats from reducing the voltage, don't worry about it.
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Old 09-22-2003, 05:31 AM
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Thanks for your responses guys - I'm still trying to sort it
Used that Mallory site to test my Unilite - and its fine both hot and cold. I've replaced the coil now, and checked all the wiring, ballast resister etc etc - but it still cuts out under load once hot.

Gonna move on to testing fuel side now as it seems like fuel starvation? Plugs are OK color, and it starts from cold straight away, just doesn't like getting hot

Anybody had similar problem? Thanks, Limey
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