[85GTR]

I drive a 85 mustang GT with a carb'd 302 with 138,000 miles on it. I have timing set at 10 degrees BTDC. I have been hearing a noise underneath my hood that keeps on getting worse, its spark knock. I have also noticed that when I put a timing light on any plug wire I can rev up the car and have normal spark, but as it returns to idle the spark hits and misses. It also every so often hits and misses at idle. I have tried retarding the timing, running 93 octane, checked the coil, wires and magnetic pickup wires on the distributor spaced them out to make sure there was no EMI. I am running a MSD 6AL ignition box (new), MSD Blaster 3 Coil (new) and a MSD Magnetic pick-up Distributor (25000+ miles). After I changed the box and coil for a newer one it ran just fine for 3000 miles or so. Could it be my box? Or could it my cam gear wearing out? I have also heard that it could be my timing chain, as it has never been replaced.

[85GTR]

Can someone relate? This is my Daily Driver I need some help.

[85GTR]

It was my Harmonic Balancer. It had slipped giving me a false reading on timing. At idle it was at 33 degrees advanced after I installed my new one. Crazy right!

[ryanw]

that sucks, im glad you figured it out, sorry no one helped, this forum has slowed down this past few weeks so dont let this reflect as the normal operation around here, were more then happy to help when we can.

[79fox]

i bet it slowed cause everone is out working on there car in stead of sitting inside with snow on the ground dreaming on here lol

[69fastback]

Glad you got it figured out. I'm just going to throw something out there that may help in the future.

With an MSD ignition, make sure you're not using an inductive timing light with an adjustable dial on it, or you'll never get the timing set right. They use magnets, and it will totally screw with an MSD. Cheap ass timing lights are about all you can use, or you can mess it up.