You are correct and I'll check the voltages to see if there was a change there since install. There are probably 30 suspects to check. My original question was asking where was a high probability to check first. Everyone has offered something to put on my list but no "Most Wanted" suspect yet. No point in wasting time checking something that is unlikely to add to this.

 

I still amazed on the amount of people with aftermarket coils and yet all five of my dad's cars and my Chevelle still have assembly line coils working just fine.

 

FIFY
Just for clarity for anyone reading this in the future, the ballast resistor was replaced with a fusable link <nichrome resistance> wire for '68 onward.



thanks Dan

 

Here's the thing in answering your question. With old cars using their original type components, ignition, carb, mechanical pump and so on, any one or more problems can cause any one or more running problems. Modern cars report their problems with codes, our old cars depend upon old car experience among those diagnosing them. In the old car world we were brought up taught that one should always look at ignition first, especially with intermittent or one in a while hiccups. The logic being that fuel flow through a carb is mostly steady state. Of course this is prior to ethanol in our fuel and the damage it can cause to incompatible rubber parts.

Still, based on what you describe I think the old rule of thumb applies. You've received a variety of answers because any one of 10 things can cause your problem. The answer to your question is look at spark first and in order to have spark the wiring through the bulkhead harness connector is a sore spot on these cars. That is why I wrote to check there first. Your MOST WANTED as you put it:

1. Bulkhead harness
2. Points, condenser, cap & rotor
3. Plugs and plug wires

Avoid throwing parts at it or making a bunch of changes that will not inform you as to what actually caused the problem.
One thing at a time, try it, then try something else, try that, and so on. If you keep at it methodically using patience, you will find it. When you do, it will be stupid. I guarantee it.

Dan

 

Nichrome resistor wire is what I believe you meant.

Dan

 

Go for the simple things first, check those points and the dwell.

 

From your comment in post 17 I’m going to second on plug wires - but could be a number of other things too. If you can, fire it up at night with the lights out and watch the motor for awhile for signs of plug wires arcing to the engine. The repro wires are really poor if those are what you have,

Are you running points or something else? If so check for worn, pitted surfaces on the points and the dwell.

 

check the ignition..coil

 

I also learned something. I thought all 1964 L76 and L84 had TI - nope. I believe I though this due to all 1966 L72 having TI.

To the question, I suspect bad gas. Additive, drive, refill. If it was an issue under a VC, it would make a racket. A good visual inspection is also a solid starting point. Good luck!

 

only 65-69 solid lifter Corvette BB had TI as standard and was required. It was a option on any SHP engine for 64-71 Corvettes, 66-69 Chevelles 67-69 Camaros Not sure on Impala BB cars but I would think so

 

thanks, yup that's what I meant!

 

I agree with every comment on simple fixs first: tuning, timing, Ingition....The only reason I mentioned Ignition Coil is because on my 61, after a day long Chevy car show in Pittsburgh, my engine stumbled out of the show parking lot. And hesitated (Bucked) at cruise. When I got home, there was oil in a rear recess of my intake manifold under my IC. This might be very unusual, but there was a crack in the IC cap and one at the base...At the time, I had no idea there was oil in those coils!!! Changed the coil with a NAPA product....All good!

 

This was my experience with a coil.

 

OK, I started checking the easy stuff first.
1. Gas tank was installed new in 2014. Looked sparkling clean inside. No signs of residue or water visually. I added STP gas treatment three days ago and have driven about 25 miles with that in the tank.
2. Look at and tugged at my bukhead connector to see if it was loose. Not loose, but still could be a bad contact within the connector. Saved that checked for later.
3. Took out my 2 year old AC Delco coil and checked it against specs from two sources of data. Positive to negative terminal = 1.7 ohm. Right on data as stated. Positive to center terminal = 8.86 ohm. Data from both sources said this should be 11.0 or higher, 13+ is good number. So I thought I had the problem solved. Went and bought a new Duralast coil. Put it in, drove around and wah-la! Ran great for 5 minutes then started bucking again. Took the new Duralast coil out and checked it. Pos to Neg terms = 1.7 ohm. Pos to center term = 7.9 ohm. Worse than my old one. Took it back and exchanged it for another, same model. Checked it in store and got the exact same results. So I'm thinking bad data from two sources? Or I don't know how to use my multi-meter? WTF.
So I put my old coil back in and said, New POINTS? I looked at the contacts on my existing points and the stationary contact was erroded to a cup that the moving contact fit nicely into but I'm guessing that changed the gap significantly. The stationary contact actually had a hole burnt through the center about 1/3 the size of the contact.
Got AC Delco points #D1007 shipped over night. Put them in and got NO ignition at all. Crank, crank, crank. Nothing. Took the new points out, put in my old points and I got ignition, but poorly running. So why the hell do new points meant for this engine, not fire?
I have to stop investigating at this point until I understand why brand new coils don't meet specs and why brand new points don't even give me a spark. Any thoughts??? Or advice on these two questions?

Thanks, Craig

 

Double check to make sure the points are installed correctly and the two wires are connected to the points. Make sure the ground path is good from the distributor to the engine block, the primary current circuit through the points goes to ground through the engine block. Did you change the condenser?

 

Also check continuity between all your ignition circuit like the lead black wire from the dist to coil.

 

How did you set the dwell on the new points? Feeler gauge prior to start up? If they were not gapped prior to start they may not be closing, or opening.....

What about the condenser - replaced?

 

Set points with feeler gauge to .019 with lobe having contacts as close to full open as could be detected.
There is continuity from coil negative to ground (engine block).
There is 12 V +/- 1 to the coil positve side with ignition ON and in START. No flucuation in voltage. Balast resistor is also less than 1 year old.
There is no spark at plug #3 (easy to get to) when engine turning over.
There is no spark at coil out line to distributor when engine turning over. Is there a way to test coil output voltage?

So with NEW points installed and connected correctly and either the old or new coil in place, I get NO spark to plugs.
Old points in I still get spark, but really BAD missing, etc. They are not repairable, contacts are shot.
Unless I missed something, I'm going to get a cheap set of points and another condenser, install them and try again.
Spark plug wires - AC Delco 9508N new June 2020.

If I get some kind of fire with old points in and NO fire with new points in AND everything is the same otherwise, you have to suspect the new points are bad. (But I see it, I just don't believe it).
Repeat: Is there a way to test coil output voltage?

 

OK, here's another bizarre question. The point set I took out that had been runnning fine (for a while) has what looks like a condenser included (installed on the point set within the dizzy cap).
See pic. But there is also an external condenser connected to the coil positive terminal. I have also seen points for '64 Corvettes that do NOT have the included condenser. All the parts sights I have looked at offer both types of point sets for my Corvette. So how do I know which to buy???

 

One is called a uni set which has both points and condenser while the other traditional points and condenser are separate.