sprink94

So in fooling around with my issue I looked at the Opti very closely and took these pics.



I think this is what I have:https://documents.holley.com/83811.pdf
There is a vacuum line that exits the bottom of the distributor at about 6 o clock...snakes up thru and behind the alternator bracket. It continues beneath the driver's side Injector cover and has what appears to be a check valve inline on it's way to a connection on the rear of the intake manifold.

I'm thinking the screw at the top allows for timing adjustment.

Understanding this, does anyone on this forum have experience with this Opti? The vacuum line looks "Factory" to me. I have had one "Old School" Mechanic tell me that on the 1994 LT1 Corvettes the factory made a mid year change to use the vented Opti. He is going to take a look at my car Thursday.. My car left the factory in January 1994 so it may have had this revision.

rklessdriver

The only 1994's that got the pin drive Optispark from GM are B Bodys... Impalas, Caprices, Buicks and Caddys. Corvette and Camaro/Firebird didn't change until 1995.

I can verify from your pics that you do have an aftermarket MSD Optispark, which came with a retrofit vacuum harness.
Will

sprink94

Thanks for your reply. I suspected that it may have been an original vacuum instal due to the OEM look of the vacuum harness. I understand that the vacuum harness is a unit part with no serviceable elements. I'm thinking that the PO may have retrofitted a vacuum hose set up for a '95/'96 with an over the counter purchase from a GM dealer at some point.

Interesting GM/Buick Service video I found on Youtube with an excellent description of the ABITS (Opti) distributer and the troubleshooting procedures for it.: .

I learned quite a bit watching it.