GM HEI no spark for 30 sec. when cold
 

350 SBC with hydraulic roller and Q-Jet with 4L60E trans in my 68 El Camino.

Not resto, but definitely technical. Even with a jumper wire going directly from the batt + to the + on the distributor cap, I get no spark for the first 20 or 30 seconds (OK, maybe 15 to 20.... haven't timed it, but I am used to the cars starting right up) if the car has been sitting a day or more.

Once started and warmed up, starts in a nano second. It is NOT starving for gas. Has electric fuel pump so I can get gas to the carb without cranking.

Tried two distributors, and both did the same thing. Tried a new coil. Same thing. New pick up; same thing. New module; same thing.

Other than this, the car runs great. Got 24+ mpg on a 300 mile trip, unloaded. Pulls an 8000 pound load without any issues.

Any ideas? I have a bunch of old point style distributors, so may put one in the old Sun machine and curve it so I can try it out.

Just a stab at this -- have you an engine to fire wall ground wire? Also, you indicated two different distributors -- did you use the same cap and rotor, etc.?? Have seen rotors with an arc burn hole thru to ground. Good luck! TAZ

Thanks Craig.

Two distributors and three caps.

Two engine to firewall ground straps, and another ground strap from engine to frame.

I've run many HEI distributors, but I've never seen this before.

Tell me about it. I have virtually the same set up in my farm truck, same cam, same elec. fuel pump. I turn on the fuel pump in the farm truck; let it run about 10 sec. pump the accel one time and it starts right up, even if it has been setting for a few weeks.

Hate to convert to points, as I will have to change out the ends on the plug wires, and run the 12v wire from the solenoid to the distributor to give it a full 12 volts when cranking. That wire is missing. It was already converted to HEI when I got it.

You can get a cap from MSD that has the same spark plug type terminals on it as the HEI cap. Still, seems like there should be a simple cure for this. You have already done everything that I would have done. I have a test HEI that I have installed in many different engines to either prove that the ignition is the problem or it isn't the problem. By using a different distributor you have done the same thing.

I have one more HEI here, but it is in the farm truck. I was thinking of going with a small body hei in that vehicle as the firewall clearance is really tight. Maybe I will try that distributor in the El Camino. When I put each of these on the Sun distributor machine, they all performed just fine.

Strange problem. Have you checked the thin wires from the trigger coil inside the dist?
They move with the vac. advance and are prone to breakage.
They may be broken but still in place and making contact when vacuum builds.
Long shot but worth a look.

Just ordered a small body HEI for my Studebaker truck. Will try the distributor out of the truck.

I had one other idea, but was a no go. There is a wire going to the "tach" signal for the transmission controller. I thought maybe that was causing an issue. Unplugged it, and still had the same problem.

Will report back after I change out the distributor... again.

Is the internal coil ground strap installed for the coil. It goes on one of the coil screws in the cap and goes to the middle pin on the 3 pin connector. Also make sure it has a good ground if there. 2nd attach a 12 volt test lamp to the tach lead while cranking, it should immediately flash on and off while cranking. That will tell you if your primary ignition cuircit is working properly.