So I have a 1964 Sport Fury... stock internal 440, stock 906 heads, 484/284 cam, performer rpm intake, 750 Holley... Electronic ignition conversion i found online, 3000 converter, 4.10 gears, etc...

Ran good, but figured out that the ECU box it came with was orange, but not the mopar orange box. SO... I bought a mopar chrome box... Thinking it would obviously run better... right?

Well, swapped them out, and after 4000 rpm, it starts to pop through the exhaust... and now a day later it has developed a miss. Like its fouling a plug... it comes and goes at the right throttle position, but when I hammer it, it is missing...

So, I need help from my mopar friends... PLEASE let me know what could be the issue. I have not messed with it. Parked it, scratched my head, and walked in to post this.

ALSO - What spark plugs should I be running? I have a set of expensive Iridium plugs in it now... and like I said, it seemed to run pretty good before I swapped boxes. Car weighs 3800 lbs with me in it... ran 13.29 @101...

Please sound off...

 

If it is missing at idle, can be found by grounding each plug/plug wire.

After that I would be pulling all 8 plugs, keeping them in numbered order, and give them a read.

If the plugs give the answer then you can focus there. I would not replace wires, cap and rotor all at once as it may hide one simple fix, diagnose and replace one component at a time to know if you actually got it.

 

My 2 cent....
1... Put the old ECU back in and see if that solves the problem....
2... Put a set of Autolite #85 or Champion RJ12YC in it and see if that helps it...

FYI.... Orange box is a good box.... I think the new Mopar Performance ones are Black?????
But if the box is bad... Return it... and Opted for a box from FBO... You will like that box much better...

 

The orange box I have isn't a mopar box. Its a look alike. aftermarket. So I think it isn't what I hope it is. You know? I thought the chrome would be a guaranteed upgrade. At this point, Im considering a Rev-n-ator box... Really frustrated.

 

Welll............maybe it's the box and maybe it "aint"

Check power to the box. I don't just mean "see if you have power" I mean see if you have very close to "same as battery."

These boxes MUST be grounded

This could be a bad coil along with a number of other things including an open plug or coil wire, or what is known as "distributor phasing"

It could also be a valve problem. Maybe you tweaked a valve and it's sticking, or you have an exhaust lobe going flat.

 

Broken valve spring.

 

Mike I think the Mopar boxes use a ballast resister. These reduce the voltage going into the mopar boxes. Having said that you said you removed an orange box which is not mopar. So do you suppose the orange box was getting the full 12 volts and you switched it to a mopar box , if the mopar box gets the full 12 volts you could be doing damage in your motor.ie: burning up plugs,pistons ? I remember when I changed my mopar to MSD ignition I had to remove the ballist resistor because MSD run at 12 to 18 volts. Do what people have been telling you. Get a multi meter and check your voltage. Pull your plugs and check them. Also try putting the box back on it came with after you look at the plugs. One thing at a time.Good luck

 

UPDATE -

Switched the boxes back out, and same problem... so I pulled the cap, and it is a mess.... so maybe it was just a dumb coincidence that it happened to go south when I installed the chrome box...

So Ive ordered a mopar cap and rotor, new wires and a set of new RJ12YC plugs...

We will see if the problem goes away.

 

Good Deal.... If that much works out.... Then you can work on some of the other pieces of the puzzle.....
Will Stay Tuned

 

UPDATE!!

Great news... I changed the cap and rotor... and also went ahead and ordered a set of the new ceramic accel wires for a 440... ( Heard I may want them for my TTI Headers...)

In the process I found two bad wires, burnt pretty good and cracking. They were not very old, so Im bummed, but happy it was a simple issue...

Put the chrome box BACK in and it runs GREAT... SO happy.

So it was a really bad coincidence that when I changed the box the wires went to hell...

WHEW!!!

Thanks everyone for your help...

12's here she comes... not bad for a 3750 lb car with me in it...

 

Glad you found the problem.... Might get 8 of the plug wire heat boots to cover the wires and boot if it look like its going to be much of an issue.... Well Keep up posted on how she runs..... Come Onnnnnnnnn 12's..... Let the fat lady sing....
Will Stay Tuned...

 

FYI... Your orange box should be good to around 4800 RPM should you not need to buzz it past that... Good spare depending on whats happening...

 

I have several nos Orange box and crome box's, pm me.