I had installed a 57 distributor on my 312 two years ago. With it a Pertronix ( original) with the flame thrower coil 1.5 ohm.
New high performance wires were also installed. 15 degrees of advance on the crank at 500 rpm with vacuum advance disconnected.
Vacuum advance is working.

It has always had a misfire at around 1500 rpm, but it seemed to clear up above that.

Now the fun starts: I took out my toploader and installed a mustang GT 5 speed. upon completion the car had developed a bad misfire in the 1500 rpm range. When below that it appears OK and if you get past that point in rpm it also appears OK.
Thinking that maybe I cracked the distributor cap. Replaced it and the rotor. Checked all of the plug wires. Installed new plugs. Set the valves, did a compression check.

What am I missing? The intake has not been off the car. The dual 4V carbs have not been changed.
I am at a stand still.

Hope you all can shed some light on where I should look next. I have not checked the engine to firewall ground strap. I have also not checked the internal distributor ground wire.

Jim

  Jim Rowe Elkhorn, NE

Jim:

Since this happened with the distributor change, my guess is that at 1500 rpm you have too much advance. That is probably when the vacuum advance starts to pull in, and you already have plenty of centrifugal and initial advance. As a quick check, unhook the vacuum advance and see if the miss goes away. If it does, you will need to tweak the advance curve in that rpm range.

John - "The Hoosier Hurricane"

John,

Glad to see you back on the forum. I hope you continue to get better.

I did retard the timing to 12 degrees. This along with the vacuum disconnected did not cure the problem.
I ordered parts on Sunday. They arrived today.

Put on the new coil. A little help was seen. Then I installed a new Pertronix Igniter II.
This solved the problem. Oh does the transmission gearing make a difference. This car now runs HARD.

Will take it to the local 1/8 mile track. When this happens I will post the times.

FYI: This is the third Igniter that has been installed, two of the original and now the Igniter II.

Doesn't speak well for the product. I have always used the recommended coil from Pertronix.

Oh well I did get a through tune up and valve adjustment out of this ordeal.

Take care John.

Jim

  Jim Rowe Elkhorn, NE

You should have gone the ignitor 3, Multispark and a rev limiter if you running it hard.. Make sure you getting the full 12 volts to it. Set it up with the dissy out and watch for excess movement in the shaft and plate etc. I haven't had any probs with any of mine.



"Came too close to dying to stop living now!"

Are you also using the Pertronix coil? I've heard the Bosch GT40R is also ok?


South Australia

Jim. Glad you located the source of the problem. The ignition module would not have been at the top of my list. The Ignitor I’s have been problematic but I’ve had no issues with the Ignitor II’s and III’s. Just be sure to use the Ignitor II’s and III’s with a straight 12 volts and without a resistor.

Lorena, Texas (South of Waco)

Ted,
Thanks for the reply. I do have 12volts to the coil. I had 12v with the original ( 2 ) previous ignitors I units.
Glad to hear that I am not the only one who had problems with these. I didn't think I needed the rev limiter so I purchased the Ignitor II.
I think I will get another just as a pack up.

Keep building those super Y-Blocks. You are MR. HORSE POWER!

Jim

  Jim Rowe Elkhorn, NE

Jim,

I had such a backfire in my 292 T-Bird. Checked or changed every thing but eventually found the power wire inside the distributor had lost some insulation and every time the plate advanced, it would short out the entire ignition. Of course, then the advance would go back and the ignition would fire up again after getting the cylinders loaded with gas. Tremendous backfires. Blew the passenger side chrome tip right off the exhaust pipe. Just another place to look.