I'm convinced my previous Accel 300+ ignition and my present MSD 6Al are killing my optis.

My first opti that came on the car lasted me over 60,000 miles. Then I installed the accel 300+ ignition. The second one lasted me 10,000 miles. Third lasted me one season. Then installed the MSD. Fourth lasted me 2 weeks. And my last one lasted me 2 months.

No, they don't get wet. I've installed them myself 3 times and once by a dealership.

Only thing that makes sense is that the higher voltage from the ignition boxes are frying my optis.

Planning on running my next MSD opti without the MSD 6AL.

 

Do you think the Mallory 685 box has similar effects on the optis? Just wondering if I am playing with borrowed time now that I recently installed the Mallory box and I am still using the stock opti with 94K on it.

 

i ran a 6al for 2 years and never had any opti problems

 

My local GM dealer told me that the higher voltage reduces the life of the ignition components.

I was just wondering if other people had similar experiences with the life of their optis.

 

In general, I agree with that.

But, assuming all the parts are in good shape (like no opens in the high voltage wires), regardless of the ignition system's voltage capability, the voltage it takes to jump the spark plug gap is what determines how high the voltage will rise on the secondary of the ignition system.

The main factor (there are others) that determines how high the voltage will rise on the secondary is the cylinder pressure. The higher the cylinder pressure the more voltage it takes to jump the spark plug gap -- and, that voltage is developed across the entire secondary of the ignition system, including the cap and rotor.
So, more power means higher cylinder pressure and that means a higher voltage is needed to jump the gap. Therefore, when you modify your engine, it can potentially take more voltage and cause more arcing inside the distributor.

The thing to keep in mind is, as soon as the spark jumps the gap in the spark plug, the current flow loads the secondary of the ignition system and keeps the voltage from rising any further.

That been said, the Accel unit probably can cause the voltage to be able to rise higher, if needed, to jump the gap, where the stock system may misfire because it couldn't jump the gap.


Tom Piper

 

I have said it time and time again,use .035 gap on the plugs. The bigger the gap the harder it is to fire and the more resistance ya have in the system to back up at least part of the high voltage into the opti.
RPM's don't help it either.

 

I've been running an MSD 6A for more than 5 years and have had an opportunity to look at the cap and rotor in the mean time. I saw no evidence of extreme or accelerated wear to make me want to remove the ignition box. Of course, my car is lightly modded and street driven.

 

What part of the Opti has failed on the 5 units? Cap/rotor? Optical sensor? Does the damage appear to be related to high voltage - burned contacts? Or is it more related to mechanical damage - the rotor being pushed into the cap?

 

I've opened 3 of them. 1 had the plastic rivet fail. The other two I couldn't tell. They seemed to have a tinge of blue on them.

 

This is just my personal opinion, I have no proof of this.

The AC double-platinum plugs, that came stock in the LT1, were notorious for losing platinum pucks.
When I took my engine apart at 55K, only two plugs still had all the platinum pucks on them. This causes a much larger spark plug gap.
That larger gap would cause the secondary voltage to rise much higher, under the same circumstances, and put more stress on the Opti-Spark.
I wonder how many Opti-Sparks wouldn't have failed if the plugs didn't have problems first?

Tom Piper

 

Tom.... I think you're on to something. Both Delteq and MSD suggest that the stock cap dielectric strength breaks down under very high voltage or (per Delteq) use of multiple spark discharge. MSD claims a higher dielectric strength for the cap. When the dielectric properties are loss, you get cross-firing between the conductors embedded in the cap to route the high voltage buttons to the cap wire towers.

Your experiences would be in line with mine. My original Opti failed at about 60K miles. The seeming failure mechanism was blinding of the optical sensor by rust from the low quality steel bearing retainer. The cap/rotor showed no visible signs of stress. But for the last 30K miles of the Opti's life, there was an underlying rough idle that was impossible to cure, suggesting that in addition to the rust problem with the optical sensor, there was something else going on with the high voltage portion.

My first set of plugs burned badly and lost the platinum pucks (although the wear and tear was aided and abetted by the use of nitrous), and my second set lost 1/2 of the pucks in the next 30K miles (no nitrous use).... so badly that the 0.100" gaps and the MSD-6A box were causing the Taylor 8mm wires to cross-fire to the point where several of them burned right through the carbon conductors.

I'd be more suspect of the excessive gaps in the poor quality stock plugs than I would of the use of a multiple spark box.

 

I'll throw in an addition to my previous post of not noting excessive wear on the cap and rotor: I have not had a problem with plug gaps opening up.

 

what kind of plug should you run with msd 6al and coil have not had any promblem with my opti just that the plug go every so many passes

 

You might wanna try some Bosch Platinum +4's. They come from the factory pre-gapped.

 

You really shouldn't use any platinum plugs with hot ignitions. Platinum is a softer metal and will wear faster with a hot ignition. My factory platinums were blown to bits after my first 25k miles with a 6al and hotter coil. Never ran them since. By the way, i've run the same 6al for the last 11 years with no issues to the MSD or OPTI. My first opti went 60k and ran and idled like a champ with no issues. The only reason i changed it then is cause I was doing the heads and figured since I was in there that far that i might as well put an opti on.

Ken R.