I sold a customer an MSD 83811 opti (95+) which he installed himself on a 383. He says he started the car and it ran fine for about 5 minutes, then started backfiring out the exhaust and acting like plug wires were on the wrong plugs. (He is running a Delteq ignition) He brought it in to the shop, and the first thing I did was bypass the Delteq to take that out of the equation. Same thing. I removed the opti and pulled the cap to find that the rotor had been rubbing the cap and eaten it up pretty bad. The opti wheel had broken in a spot, and eaten the pickup from where it had been passing through it. Upon further inspection, the bolt that holds the main shaft in the opti (where the optical wheel mounts) was extremely loose, and you could move the opti drive shaft back and forth a great deal. I put another MSD opti on the car, and it ran great for about 2 minutes before displaying the same symptoms. I pulled the opti back off and when you turn the drive shaft, you can hear the opti wheel contacting the pickup every 180 degrees as if the wheel is warped. That one will be going back as well while I put a Delco unit on to try and narrow down the issue. The dowel length is not an issue. It is around .600" and nowhere close to bottoming out in the hole. Anyone experienced this problem? Thanks

 

I know there were some initial MSD optis that had problems, if that is what you mean. So, does it run fine with the GM opti?

 

There was a case of an early MSD having the rotor rub on the isolator that separates the cap section from the optical section. But if the rotor is being forced into the cap, and recognizing that it is a stroker motor (meaning a cam change), you might ask him if he checked the cam dowel pin length.

 

I'll be trying the GM opti tomorrow to see if it does any better. This unit should be a fairly recent piece, as I ordered it in the latest batch from MSD. I'll keep you posted on how the GM piece does.

In my initial post I said the dowel pin length was .600" which is close enough to spec. (on the short side)