robertstjean

1968 coronet had a 318 changed to a 440. Motor is new and I converted the distributor to electronic with all oem parts. It runs great but has a high speed miss. Can it be the ballast resistor? It also has a new coil,carb.
It is all new under the hood can someone help me I am lost about to give up... Thank you...Robert

62Furious

If you are running a factory electronic brain box will let you rev to 5500rpm, you may want to get the orange box

robertstjean

Thank you 62furious, The conversion kit came with wiring harness, orange box and distributor. It is all there but it also came with it's own ballast resistor. What do you think about bypassing resistor and giving the coil a full 12V? I also herd that some coils don't need a ballast resistor, can that be true...Thank you for all your input. Robert

Archer

Robert -

The Mopar ECUs need the dual (4 prong) ballast resistor, or you'll start burning stuff out. Some coils, like the old Accel SuperCoil need a second single (2 prong) resistor as well.

Re the high RPM miss, what's high RPM??? Check your plug wires for arcing or loose connection. Best to rev the engine at night and look for electrical arcs / sparks, especially near the headers/exhaust manifolds.

Archer

robertstjean

Thank you Archer, The resistor that came with the kit is a 2 prong. The miss varies from approx 2000-2500 rpm and up. It mainly is under a load
it won't do it in my shop when in park or nuetral and I bring the rpm's up.
It does it when I am driving and give it the gass. They are new plug wires but they are cheap ones. Thank you for your time.........Robert

440roadrunner

NOT ENTIRELY TRUE

The OLDER Mopar boxes are so called "5 pin" and MUST have a 4 terminal ballast

The NEWER Mopar boxes only USE "4" of the pins and CAN use a 3 terminal ballast.

YOU CAN NOT TELL by looking because at least some boxes physically have all 5 terminals.

Since this came in a new kit, I would assume it is correct the way it is.

YOU are correct, that some coils need an additonal ballast

Coronet 500

I would check your total timing, amount and at what RPM (no vacum advance connected), then pull your plugs and check the colour.