I have a 94 corvette that needs an opti spark but there are so many brands I dont no which is better and I want one that will last. Any suggestion?

 

I would personally look for a GM Delphi replacement. I have seen cheapo auto zone ones run fine for many miles also. Its like playing Russian Roulette.
Change the water pump while you are at it.

 

Tried a new Delphi unit. Cost $395 and only lasted a year. Did get my money back though.

Unless you can find a real genuine AC Delco NOS unit, I would personally go with the one SaccityCorvette sells, or a vented Petris unit (which is the route I went). These two optis seem to be the best available right now, and they both seem to use the same components. Both company's claim to have a "Mitsubishi Grade Optical Sensor". None of the other manufacturers, as far as I know, even mention that.

It's really a crap shoot these days. Such nice cars, but no real high quality parts available.

Your only other real choice is to upgrade your timing cover to a 95/96 and use the later pin drive opti which is vented from the factory. I believe the 95/96 NOS AC/Delco units are still readily available and are a little more affordable than a 92'-94' unit.


More knowledgeable people will chime in I am sure. PAGING DIZWIZ!!

 

I went with the GM Delphi got it from summit for about $360 after tons of research what ever you do don't buy a cheap one.

 

I've heard that even the newer Delphi units are now using 'off shore' electronic sensors inside just like most of the other cheaper offerings.
I bought an AIP Opti for a little over $100 and it has a very good electronic sensor said to be built to Mitsubishi specs. The case is as good as most other off brands I guess (not great but good enough). I sealed it up around the wire input hole with "The Right Stuff" gasket sealer just to make it as water tight as I could. It is a vented style so hopefully it will stay dry & clean inside. It's gone almost 3 years so far and been on many multi-tank length cruises with no problems.
Previously I had gone with a very expensive MSD unit that never did run correctly and eventually failed completely. I chased that problem looking at every other system, believing it couldn't possibly be that brand new expensive piece, but it was!
The one on there now is cheap enough to replace with another if it should ever crap out and I'm still hundreds of $$ ahead of an expensive one. I don't like repeating a repair, but like said above, it's kind of a crap shoot for quality anyway so why spend more than you have to.

 

I have a '94 coupe and just did mine last year.

They're kind of pricy, but I had my mechanic install an MSD unit as they seemed to be one of the least troublesome. A good optical sensor is important.

I would suggest doing what I had done and create a forced air ventilation system to prevent moisture build up and corrosive gasses formed by the high voltage. This was a big problem in the early LT-1 Opti-Spark units.

Ozone generation occurs when oxygen molecules react in the presence of electrical discharges. Ozone combined with nitrogen and moisture in the air forms nitric acid which reacts with metal surfaces causing corrosion and failure, and cause conductive paths in the distributor resulting in miss-fires and cross-fires.

Since ozone is heavier than air it settles in the bottom of the distributor. The Opti-Spark has a passive ventilation system consisting of small hole(s) at the bottom. This passisve system worked, but a forced air system works much better.

A small diameter fresh air inlet was installed from the rubber intake plenum right after the MAF sensor to the Opti-spark and then to the intake manifold to draw clean air through the distributor and prevent corrosion causing ozone/nitric acid build up.

I didn't have this step done but I would also suggest having a small air filter installed on the hose right before it goes into the intake to prevent gases from entering the engine. Also a one-way check valve somewhere on the hose right after exiting the distributor to prevent back flow into the distributor.

This is how the later Opt-Spark units were done.

P.S.
If you install this forced air system, make sure the air inlet line is never pinched or plugged. If it ever is, it will draw a vacuum on the distributor causing a miss-fire. If vacuum is strong enough it can pull the distributor cap down and contact the rotor.