Technical Early Hemi Power to Coil but No Spark?

I’m going to swap coils with the truck and see if that does anything.


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Just took the coil off the ‘37 and put it in the ‘65 and it fired up. Problem isn’t the coil. Neither coil works on the ‘37. I know this points to a distributor problem but I’m wary of buying another one just yet, is there anything else that could make it do this?


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Earlier in this thread you confirmed that you have power to the ignition switch side of the coil, and you have also eliminated the coil by swapping it into a vehicle with a known good ignition system. A bad wire to the distributor, a distributor that has no ground, or something inside the distributor are about your only remaining failure points.

 

I guess so. Still have power to the coil, 12.8 in the “on” position and 11 while cranking. We’ve grounded the distributor with a separate wire so we can eliminate that as well. I guess the only thing left to do is change out this distributor for another new one and see if that fixes it. Is there a way to test the distributor off of the engine, just for kicks and giggles?

 

Hope I can help with what I did and that was to just go to Bob at Hot Heads and get his distributor and this thing fires every time. Its almost scary, hardly hits on the first cylinder and she's off.

 

If I had known then that these would’ve given me trouble then I would’ve sprung for it, but it’s fairly expensive and I can still exchange the one I have for a new unit from Pertronix. I’m sure the MSD is worth it, though.

 

Problem isn’t the distributor, or at least not the module. The ‘65 and ‘37 both have Ignitor II distributors and I switched them. The truck has fire with the module from the ‘37 in its distributor.


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When you performed your coil test was the cap off so that you seen the distributor turn?

 

I know he replied that it turned the first time you asked; but I too have still been wondering.

 

Just figured it out, and yes the discovery is a dumb one. Apparently the distributor shaft is just a HAIR too long, and when it is inserted into the block, the shaft is pushed up about an 1/8th of an inch, and I guess that moved the magnet out of position with the module. I pulled up on the distributor housing, allowing the shaft to fall down to where it should be, and performed the test again. The test light blinked, and the coil is throwing a spark now. I need to grind about 1/8th of an inch off of the bottom of the distributor shaft, and that should do it.

 

Glad to see that you stuck with this problem. There comes a point where you work thru all the normal troubleshooting guides and techniques and all the normal things you check seem to be working, well, normally.

That's when you've got to shift things around in your brain and start doing some abnormal thinking. Normal thinking is fine for finding stuff that's stopped working as it should. But you have open your mind a bit more and be extra observant to find the abnormal problems. Like a distributor shaft that's an 1/8" too long. Or maybe the distributor housing was machined wrong. You might want to keep an eye on your rotor to cap clearances before you end up with a different "abnormal" problem.

 

So at this point do you need to check the distributor drive gear pattern against the cam gear?

 

Nope, the Early Hemi uses an intermediate shaft with a gear already installed on it, and that gear meshes with the cam gear, turning both the oil pump and distributor shaft. The distributor shaft doesn't even need to have a gear on it.

 

I know.
Was thinking the gear mesh was causing the distributor to want to move the shaft up.

 

Oh sorry, gotcha. The intermediate shaft is seated and we have the correct gear installed on the shaft, but this block was a little bit different than the one we built the first motor with. Not sure how or why, but it took us a while to get the length for the intermediate shaft to where it would engage the oil pump shaft. So our intermediate shaft may be a little bit too long, but I'd rather shave some off of the bottom of the distributor shaft.

 

It was running then not.

 

That's what makes my discovery dumb. A year ago when we built the engine, we ground a little bit off of that distributor shaft too, because we had everything apart and could see that the distributor was sitting too high because of the slightly too long intermediate shaft. Apparently I totally forgot that we did that, and when we put this new distributor in, we left the shaft as it was from Pertronix. Man I feel dumb. In hindsight, I wish we had used either a SB Mopar distributor or the MSD from HotHeads, but for now it's the Chevy dist. with the adapter.

 

Maybe that intermediate shaft is to long and have the gear wanting to clime up the cam gear.
Just thinking out loud. Is was running and driving somewhat right, then is quit.

 

By the way, thanks for the help y’all. I knew when I posted this that there was a chance something like this would happen, but y’all helped me eliminate everything else and eventually that jogged my evidently terrible memory. Now watch it not fire up tomorrow!


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I’ll look at the gear tomorrow when I take the distributor back out. Anything in particular to watch out for? It ran great for about 8 months, then started to go bad and died in the course of a week or so. Don’t know if we just got a bad module the first time or what. Maybe the rotor was still a little bit too high which caused a long-term failure?

 

Look for the wear pattern off to one side ( up or down ) of the gear.

 

Alrighty, I'll check it out tomorrow!

 

Wonder why a new performance distributor would have enough end play to permit the components to get out of alignment.

 

Did some of the pertronix kits come with a spacer for the module,put one in a VW last week and it had a little plate to use for just that purpose?. it told how to check it for distance,and clearance,might be worth looking into. Harvey

 

apologies' for what I'm going to say, as I appreciate that it may sound like an echo from previous comments that you have addressed, but please entertain me for a moment. With a jumper lead, run a cable direct from the battery earth to the engine block (not via chassis rail etc), and see if it makes any change. I say this as recently I had the same issue with a car I've been helping a friend with, doing all the same things you mentioned, and despite thinking that my earth strap was working ok, the engine struggled to fire/run well. If nothing else, should cost you nothing other than a few minutes of your time.

 

I think it’s because we have to take the gear off of the distributor so that the intermediate shaft and distributor shaft will engage. The inside diameter of the bottom of the distributor gear is too small to accept the top of the intermediate shaft.


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I might try and turn down the end of the intermediate shaft so the gear will slip over it.


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Can you better explain your thoughts on this? The gear is/should be pressed onto the intermediate shaft and depending on exactly which shaft you are using the gear location on the shaft can vary but the base of the gear will always seat on the tower bushing.

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I’m talking about the gear on the end of the distributor shaft. The intermediate shaft hasn’t been messed with, but in order to get the distributor to mate with the intermediate shaft, we had to remove the gear from the distributor because it wasn’t big enough to go over the top of the part of the intermediate shaft that sticks out above the gear.


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You might not be able to tell from this picture, but our shaft sticks out about 1/4 of an inch above the gear, unlike the stock shaft which is below the gear. That’s what I’m talking about when I say the gear on the distributor won’t slip over it.


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