604 w MSD Breaking up above 3000 rpm and misfiring through exhaust

[bluemule]

First night in new car. Has dual Msd boxes and coil. I have replaced cap rotor pickup coil and swapped from one box and coil to the other. No change from any of this. Car idles fine but will occasionally misfire through exhaust. If you rev it above 3000 it breaks up and sputters. Any help would be appreciated.

[dirtfire27]

First night in new car. Has dual Msd boxes and coil. I have replaced cap rotor pickup coil and swapped from one box and coil to the other. No change from any of this. Car idles fine but will occasionally misfire through exhaust. If you rev it above 3000 it breaks up and sputters. Any help would be appreciated.

I had the same problem a few years back, I removed the rpm pill chip and problem was solved. Can't remember if the chip was bad or the msd box, but either way removing the chip fixed the problem.

[brad hibbard]

check rotor phasing---explained on our website under FAQ tab 604/602 timing----i copied it below look at "special note for MSD distributors"

any questions or if that doesn't fix it call me

Brad
www.race-1.com


6. 604 and 602 Timing
■We recommend that both these engines be set at a TOTAL timing of 32 degrees. NOTE different amounts of timing may be benificial due to different fuels, exhaust designs and carburetor choices. However, unless dyno testing is available or controlled race track testing we advise 32 to be the number.
■For dirt late model applications we recommend that the advance curve be locked out.
■The balancer is marked out in degrees and we highly recommend using the marks on the balancer and NOT a high tech timing light with dial up advance. (keep it simple). **NOTE** the small white paint mark that is near the “0″ groove in the balancer means NOTHING. The groove is 0 (TDC) and actual degrees are marked on the balancer.
■Total timing is set with the engine hot and at an elevated rpm (even with a locked distributor). The timing actually will retard and this is due to timing chain stretch, be sure to increase rpm until the timing marks become steady.
■
**SPECIAL NOTE FOR MSD DISTRIBUTORS**
After the timing is set, align the timing marks with the engine shut off, then remove the dist. cap and validate rotor phasing. The rotor should be pointing directly at either #1 or #6, if the rotor is pointing between terminals, then the pick up coil wires are reversed and must be corrected and the timing reset.

[Egoracing]

What distributor? If you are running a brass or regular gear the cam may have eaten it.

[Steve_Hendren]

Check and make sure your magnetic pick-up wires are completely isolated from any other ignition source that carries amperage/voltage. The mag pick-up wires coming from your ignition box to your distributor, MUST BE run completely separate from any other wires!! This is critical!!! The mag pick-up takes only milliamps to fire, and any other outside source of amperage can and will induction fire your mag pick-up in your distributor!! So make sure the entire length of your mag pick-up wires are run completely separate, and do not cross over or run parallel any other source of amperage/voltage. A distance of 1" from any other source of amperage/voltage is acceptable. This is the most common problem we find on race cars. Generally people like to make nice wire looms, and like everything taped together or run through the firewall in one grommet. Unfortunately this is not good when it comes to the mag pick-up wires, and is almost always overlooked.

[MM90]

This is simple but you didn't mention it. Spark plug wires going to the right plugs? I know I have gotten a couple switched around from time to time.

[bob62]

Check for volt drop, may not be getting enough current

[bluemule]

Thanks for all of the replays. Brad gets the prize though. I put the engine in my new car and both were equipped with weather pack connectors. The issue was they were wired the opposite of each other and the wiring colors had been changed on the distributor.Brads phasing check found it for me. Thanks everyone.

[brad hibbard]

Glad to hear that it is fixed and thanks for the prize------but everyone running a MSD set up should take special note of Steve's in put on mag pick up wires -----we have also found this to be very true and Steve has it nailed on the description----most guys like to be nice and neat and in the same loom and that can bite you directly in the rear with MSD

Brad
www.race-1.com

[C10]

I have ran into this more then once myself, it is very important to check this !