Ignition Issues, Crab distributor

[BIG KEV]

Here I am, I have been fighting a weird issue with my 34. It's a hopped up 59ab, rebuilt with 2k miles on it now roughly.

So I have had a weird issue, sitting and idling after its warmed up, it will bobble a bit, and start to feel off. Power is still great, no issues driving it but idle is the issue. Been through the carbs 10 times, I have swapped out to a new carb for testing, went down to 1 carb and still did the junk to me. Thought it was vapor lock, added a inline electric fuel pump and no resolve. I also changed from a 3 ohm internally regulated coil to a external regulated coil with a ballast resistor. New points replaced the stock 1942 set that was in there, I have had 10 condensers installed, cap, rotor, etc. I am running a nice set of Noble Speed solid core plug wires and NGK plugs

NGK B8HS10
Standard Coil UC12T
Standard Ballast resistor RU-13T

This made the issue less frequent, but engine temps over 180 she will do it. I can make her do it pretty easy now. Once she dies, sometimes she will restart sometimes not. A few days back I was stress testing her and she did it. Dies out and wouldn't restart. Tested spark, it was still blue but jumps about 1/8" instead of over a 1/4" It was doing. So I Jumped the ballast resistor, fired up instantly. This shows some of the issue, I know I could put the starter button with a diode and get 12v to the load side of the ballast resistor to fix this issue, but I am after the main issue plaguing me here of dying out.... The internal resisted coil made this restart issue, having to wait 2 to 5 min and it would restart. Coil has always gotten warm, even with the ballast resistor now it gets warm but not as hot as the internal resistor one did.

With this said, I've seen alot of people aiming for 3 ohms combined to keep the amperage down. Everyone says under 3.5 amps is key.

12.5volts, 3 ohms = 4.16 amps on paper, tested in real life = 4.25 amps

14.5 volts running at 3 ohms would be 4.83 amps.

Ohms law doesn't quite figure in thermal loss and resistance changes but still I am well into the 4 amp area.

I could go to a 2ohm coil with a 2 ohm ballast and cut my amperage down close to acceptable low 3 range to mid 3.

I know there are some stellar guys here who have fought the fight longer than I have. Just looking to get this car dependable again. It's done it in the cold weather but mostly does it in the 85 degree and above here.

Thanks in advance.

[koates]

Vacuum leak somewhere. Get yourself a vacuum gauge and connect into the intake manifold and read the chart that comes with the gauge. Regards, Kevin.

[Terry,OH]

I also suggest the vacuum gauge. Have you tried to remove the idle mixture screws and check the small passage is clear. Each screw should effect idle if one does not that is the one to check.

[BIG KEV]

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Originally Posted by koates

Vacuum leak somewhere. Get yourself a vacuum gauge and connect into the intake manifold and read the chart that comes with the gauge. Regards, Kevin.

Originally Posted by Terry,OH

I also suggest the vacuum gauge. Have you tried to remove the idle mixture screws and check the small passage is clear. Each screw should effect idle if one does not that is the one to check.

Thanks guys.

I have thought the same. I did find one vacuum leak on my Sharp intake that I was using, pulled it off and put on my Offenhauser 2x2. The bad part about the vacuum port on these dual planes is its only getting signal from 4 cylinders of the motor. I have found this test to be a bit off at idle as well since the isky 1007b cam has a nice overlap. 12-15 at idle, Off idle I get 15 to 18, 1200 rpm I am over 20. Verified by my motorminder gauge inside.


Terry, I had both bases apart, full clean, rodded passages out, upper transition slot and lower with .030 welding wire, no obstructions. Every screw will do exactly what it should. Both carbs were synched with an airflow synch tool. The front base has a little more side to side play in the idle screws than the rear, but they sill seat just fine. Emulsion tubes have been replaced, carb tops were re surfaced, these Largo Logo Stromberg 97s have had the full gammet done to em.

I have the o-rings on all the intake valve guides when I built it, and 175 psi average compression across the board.

5 min of idling the coil will be warmed up while the block is still cold. I did a amp test running, I am averaging 3.2 amps running with current setup after 5 min. Voltage to the coil after ballast resistor is 7 volts running.

I am thinking these Standard T series coils may be the issue, I have heard alot of things lately on their quality being junk these days. I went ahead and ordered a Bosch 00012 to see how that goes. Fingers crossed!