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Old 07-12-2016, 04:27 PM
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HEI questions

Have an HEI in my 74 Nova with 350. I purchased the car with this distributor in it. Have the updated control module, new cap and rotor and stator wires are fine. I don't know for sure about the coil. When I set plug gap at 35 it runs good with a mild or slight miss. When I open the plug gap to 45 it misses even more. Any ideas?

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Old 07-12-2016, 05:29 PM
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Originally Posted by Firsttimechevyowner View Post
Have an HEI in my 74 Nova with 350. I purchased the car with this distributor in it. Have the updated control module, new cap and rotor and stator wires are fine. I don't know for sure about the coil. When I set plug gap at 35 it runs good with a mild or slight miss. When I open the plug gap to 45 it misses even more. Any ideas?
Sounds like wires may not be fine. Fire it up in the dark and see if you can detect any arcing around the plug boots or the cap. Also possible weak coil unable to fire enough juice to bridge the gap.
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Old 07-12-2016, 06:06 PM
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When does it miss? Idle? cruising? accelerating? WOT?

Did it ever run without a miss?

Crank engine while looking at spark color on a spare spark plug. Is the spark mostly white color? yellow? blue? Should be mostly a fat blue color... Whether .025" gap or .060" gap...

Fueling system could also be a problem.
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Old 07-12-2016, 06:12 PM
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Do you have a dedicated 12v power supply to the hei?
74 would of had points originally with a resistance wire to the coil.
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Old 07-12-2016, 06:21 PM
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Quote:
Originally Posted by RWENUTS View Post
Do you have a dedicated 12v power supply to the hei?
74 would of had points originally with a resistance wire to the coil.
Good point, '74-'75 the changeover period from points to HEI...

Look for 12-14 volts at the B+ power feed with the engine running...
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Old 07-12-2016, 06:26 PM
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Originally Posted by BuzzLOL View Post
When does it miss? Idle? cruising? accelerating? WOT?

Did it ever run without a miss?

Crank engine while looking at spark color on a spare spark plug. Is the spark mostly white color? yellow? blue? Should be mostly a fat blue color... Whether .025" gap or .060" gap...

Fueling system could also be a problem.
Misses at idle, cruising, or WOT. Can't tell for sure if spark is blue. Edelbrock 600 CFM carb. All I do know for sure is it misses worse when gapped at 45. Tried two sets of plug wires and is exactly the same. Thanks
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Old 07-12-2016, 06:27 PM
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Also have a fat 12 Gage wire from ignition on fuse block to distributor.
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Old 07-12-2016, 06:44 PM
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Eddy carb.s can't take more than 5 psi fuel pressure without flooding over...

Stock carb.s and Holley carb.s take 7 psi... Stock fuel pumps supply about 6 psi...
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Old 07-12-2016, 07:32 PM
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Quote:
Originally Posted by rwenuts View Post
do you have a dedicated 12v power supply to the hei?
74 would of had points originally with a resistance wire to the coil.


this ^^^^^^^^^^^^^^^^^^^
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