Been chasing a bad miss at upper RPM. Mechanic says it is one or more bad spark plug wires, (arching and grounding) which makes the computer reset and sputter even more. long story short. I have MSD 8.5MM, they only have 80 hours, (1 year) on them. Is there a better wire. I have a 526 CID whippled with a MEFI 3 EFI with MSD box. Any suggestions?


Thanks, Dave

Go to Autozone and buy a cheap set of wires for your motor...try them...and then take them back.

(We always run Taylor wires in our drag car)

think you possibly have a bad mechanic more that bad wires...those MSD wires are about the best out there...not to say can't happen...doubt it

I have seen plug wires heat up from sitting on the exhaust manifolds. They will then short out pretty quick. Be sure you get marine wires they are longer.

Run the engine at night in a very dark space with the hatch open and look for arcing on the plug wires, especially where they run near or over metal on the engine. If there is arcing, replace the wires. If the wires prove to be good, check the cap and rotor and replace plugs if needed.

Best Regards,
Ray @ Raylar

What he said. Also, you can get a spray windex bottle with water in it, and spray the wires down while in the dark and engine running. Watch for spark jumping.

Good advice Ray

Its a pretty reputable mechanic, really reputable. Thats his first thought. He also said it could be dizzy cap, dist. chaffed ground. So I think he is going to ohm the wires in morning. I hope it is wires as its an easy fix? But what are guys running for wires. He said MSD are good wires, just sometimes the terminations are suspect

First you indicated the engine has a miss at high rpms. Has the engine been scanned with a scan tool, as a high rpm "Guardian" event will act and sound like a high rpm miss and may have nothing to do with a misfire from plugs or wires?!

This mechanic MIGHT BE OUT OF HIS LEAGUE AND MIGHT COST YOU NEEDLESS MONEY!
1. 496's don't have distributors or caps, they are electronic -coil on plug ECM timed engines!!
2. Have someone put in a new set of AC/Delco 41-983 spark plugs gapped at .050" and if that stops the problem , you are done.
If you need new plug wires, Raylar has stock replacement sets at $96 per set in stock plus UPS. The Merc sets are priced at nearly $280 a set!

Either get this mechanic up to speed on Merc's 496's or get a new mechanic!!

Best Regards,
Ray @ Raylar