Bad miss above 3500 RPM

[DemonRod]

I just had an electrical meltdown on my 72 Demon with a 408 stroker motor. I had to replace the engine and forward light harnesses. I bought a year one harness for a 73 340. I replaced the harnesses and fixed the cobble issue under the hood (before I bought the car and was hid well under tape) but now, when I reach 3500 the car starts to miss pretty bad, the Tach gets VERY erratic and finally holds at 4000. The only thing that the direct short fried was the voltage regulator. I am running the chrome "brain box" and it seems fine but............... I am at a total loss as to what is going on. Any suggestions?? Any help would be GREATLY appreciated!!

 

[greymouser7]

I had a miss like this once at about the same RPM after I adjusted my ignition advance by rotating the distributer. My cam was a hair too much and I was trying to get vaccoom back for my power brakes. Initially I cleared it up with higher octane fuel.-I don't think that higher octane is your problem though (I did have the chrome ecu box)

Begin by Verifying that you have all of the proper grounds/grounding between engine/chassis/negative terminal of battery

later I found out that my voltage regulator was shot

try swaping out another voltage regulator & then a lower level orange ecu seperately

later more people here whom know a lot more than me will offer better advice, but what I have told you will get you started with troubleshooting

when testing your grounds, disconnect the battery and measure resistance/ohms

I have heard of the ballast resistor & an am meter (current meter) in the dash causing problems as well, but not specifically your symptoms

ask strokerscamp and others here, they know better than I -good luck!

 

[demon seed]

I'd change the coil first, it could have a cooked internal wire and if that don't help things swap in an orange box.

 

[DemonRod]

Thanks everyone. It ended up that I had a bad ground within the wiring box thru the firewall. I direct wired it and problem is resolved.