Opti-Spark upkeep?

[Kev70]

Hello everyone. I am a newb when it comes to LT1 engines. I just traded my Stealth for a 94 Form Firebird. I am really worried about my opti spark deal going out on me. I read about some kind of vaccum line that has to be kept clean. Can anyone help me out with this? Is there anything else that is prone to fail and be expensive? How much is labor for the install?

[Rob B (shoebox)]

There is a vent system on 1995-1997 LT1's. Your 1994 optispark does not have this. You might just start putting a little money away for when you might need to replace it. The 1993-94 optis are ~$300 if you get them at wholesale price from a dealer. There is no real way to predict failure. Some have lasted 100k+ miles. Don't worry about it until you need to.

If you were to take it to a dealer, you could expect to pay $600 on up for replacement.

[Kev70]

Would it be better if I went to an HEI conversion? To do that would I have to do a carb conversion as well? More importantly, if the thing goes out, will the car just leave me stranded or will it give some sort of warning?

[Injuneer]

There is virtually no room under the hood or the cowl for a "carb conversion" and a switch to a "conventional" distributor. In general, the only carb/distributor conversions are done on all out race applications, where they do not mind deleting the windshield wipers, hacking up the cowl, and adding a 4" high cowl hood.

There is no "HEI" substitute for the Opti. There is a reportedly upgraded billet case unit that is available as a replacement, for approx. $600. The jury is still out on whether this is a worthwhile replacement.

There is also an available add-on box that allows you to remove the high voltage function (cap/rotor spark distribution) from the Opti case, and use the stock PCM to drive 8 LS1-style coils in direct fire mode. The system requires that the Opti still supply the high and low resolution pulse patterns that define the crank and cam position.

The Opti has two distinct parts, either of which can fail. The cap/rotor section is susceptible to the same problems as any mechanical distributor, with burnt contacts, carbon tracking, deterioration from moisture, etc. And like any distributor, there may be a gradual deterioration of the engine performance, with stumbling, surging and misfires. Or, the rotor could disintegrate and everything stop instantaneously. There is no "trouble code" warning via the OBD-I diagnostics for problems in the high voltage sections.

The back section of the Opti is the optical cam and (psuedo) crank position sensor. That can cause problems as the optical sensor gets dirty. That can set OBD-I diagnostic codes for loss of high res (DTC 36) and low res (DTC 16) pulses. If you lose the high resolution pulse, the PCM will default to the low res pulse for ignition timing. The engine will continue to run. If you lose the low res pulse, the PCM can no longer identify the the true cam postion, and can not fire the injectors in the correct sequence, or fire the correct spark plug. So the PCM shuts down the fuel system - pump and injectors - and the engine will not start.

All of the problems can be exacerbated by the presence of moisture, so it is important not to get anything wet.... watch for water seeping out of the weep holes in the water pump, do not "wash" the engine, avoid super deep puddles, and some people even avoid car washes.