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Discussion Starter · #1 ·
HELP !!!
What a summer…… Driving home this spring in my when my 69 z28 started running rough. Tuned it up with no effect, still ran rough. Continued trying thing only to see the problem getting worse. I started noticing that the problem would get worse as the car heated up, but the car is not running hot. The problem escalated to the point I could only drive about a quarter mile before the car would barely run. Figured the only thing that could cause this would be heat expansion in the coil causing the car to short out. Replaced the coil and WOW the car ran 100% for about 10 Miles until the problem reoccurred at low rpm. Limped home let the car cool and the car runs fine. Could I have fried another coil again and what could cause this to happen. First coil MSD and oil came out the top after removal, new coil pep boys accel coil. Please help I’ll take any suggestions.
Thanks Dave
Actions: plugs twice
Cap and rotor
Ohms Check ignition wires
Check pertronics wires and gap
Removed Msd 6al box
Reinstalled msd box ohms checking all wires
Replaced coil
Checked and changed timing
Rebuilt holley 780
Replaced fuel pump
Replaced fuel filters
Replaced gas and added dry gas

69 z28 302
780 holley
msd 6al
 

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Dave, when it's running bad and you shut it off and start it right back up (wait 5-10 seconds or so) does it run ok or still bad? My thought here: Rust and chunks of junk in the muffler(s) are plugging things up. When you shut off the engine, the "rust and junk" falls back down into the bottom of the mufflers. Start it back up and within a few minutes, things get plugged back up again. Just a thought... Let us know how you come out.
Scott
 

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I drove a Ford truck once to Cali. that ran great when cold and bucked and farted from the carb to the muffler when warmed up, I didn't have much experience the
n and replaced many parts on that trip, only to find out that it was the condenser that caused all the problem. $1.50 part cost me a new carb, new points, new plugs, new cap and rotor, about $400 in gas and a 28 hour drive that should have taken 11 hours. Maybe that could be your problem also, I wouldn't know for sure, just giving some insight from my experience.
 

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Discussion Starter · #6 ·
good point Dave......BUT ..where do I find a list of correct coils? I checked pertronics instructions and they only push their 45000 volt coil. The msd 6 al I assume can handle any coil. The set up I am running is msd 6al, pertronics in a stock distributor and a accel coil. Please advise if anyone knows of a problem with this set up.
Thanks Dave 69 z28
 

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not all coils are campatable with msd boxs.they normally supply a coil campatablity chart when you purchase the units.i would contact msd for one of these if you dont all ready have one.i was looking on my chart and dont see a listing for your coil brand.this is a list from a few years ago thou.it might be that it is overheating the coil and shorting it out.check the voltage coming out of the coil with a meter if i remember right it should be around 9 volts.
 

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Discussion Starter · #9 ·
Thanks JRT I need to buy another coil. The car is back to only driving 1/4 mile before coil shorts out. Does anyone have an idea what would kill a coil on a easy 10 mile ride?
 

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Discussion Starter · #11 ·
update.... new stock coil today. hooked it up without my MSD box. The coil is running through the ballist resister that came with the old msd blaster coil. The system is firing on the pertronics module. The car runs but not as strong as it should. A few times after a hard pump of pedal it would power down and then pick up again. Something is just not right. please any ideas I'm about to start checking my tire pressure.
 

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have you checked the amount of voltage at the neg side of the coil while it is running?should be around 9 volts.if it is,i would start looking at the possibilty of a bad module,maybe as it gets hot its loosing some power.if you have another distribitor laying around you could try swapping it.it really sounds ignition related to me.also check your ballest resistor for cracks or damage.
 
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