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My kid (16yr old)has a 1996 Camaro SS and we think the opti spark went out. He pulled it apart and I’m trying to help him put it back together.
Is there a descent opti he can get on a budget?
Do we want to keep the Mitsubishi optic to put in the new opti spark?
The crank has a key way and the harmonic balancer does not. I know it presses on, but does the orientation matter?
Not a “balancer”. It's a harmonic “damper”, to smooth out crank vibrations/whip caused by the cylinders firing. It's the mass of the outer iron ring that is important. Not the position on the crankshaft.
Did you remove the hub? You didn’t need to. Only need to unbolt the damper from the hub, with the hub arms in the right position.
When the hub needs to be pulled (e.g. cam install) some people rotate the engine to put the arrow on the damper/pulley at 12:00 TDC, then reinstall the hub so it results in the position the damper arrow pointing up. Aftermarket dampers (e.g. ATI) include a key. People running belt driven S/C's have the stock hub keyed to prevent the hub from slipping.
The damper only bolts back on the hub one way, because the three arms are not equally spaced.
Just curious….. did you do any diagnostics before deciding to replace the Opti? Codes? Watching the tach needle - if needle moves up ~200 RPM with engine cranking, good indication the PCM is getting the required low resolution signal from the Opti.
Petris Enterprises seems to sell the most reliable Opti. Not “budget”. I've seen one report of a failure here a few years ago, and recently another on Firebird Nation. Petris replaced both units under warranty. Seemingly better results than any other available units (mostly from China - often bad right out of the box),
Not a “balancer”. It's a harmonic “damper”, to smooth out crank vibrations/whip caused by the cylinders firing. It's the mass of the outer iron ring that is important. Not the position on the crankshaft.
Did you remove the hub? You didn’t need to. Only need to unbolt the damper from the hub, with the hub arms in the right position.
When the hub needs to be pulled (e.g. cam install) some people rotate the engine to put the arrow on the damper/pulley at 12:00 TDC, then reinstall the hub so it results in the position the damper arrow pointing up. Aftermarket dampers (e.g. ATI) include a key. People running belt driven S/C's have the stock hub keyed to prevent the hub from slipping.
The damper only bolts back on the hub one way, because the three arms are not equally spaced.
Just curious….. did you do any diagnostics before deciding to replace the Opti? Codes? Watching the tach needle - if needle moves up ~200 RPM with engine cranking, good indication the PCM is getting the required low resolution signal from the Opti.
Petris Enterprises seems to sell the most reliable Opti. Not “budget”. I've seen one report of a failure here a few years ago, and recently another on Firebird Nation. Petris replaced both units under warranty. Seemingly better results than any other available units (mostly from China - often bad right out of the box),
The car basically sat for 2 years needing a clutch until a month ago when we got it. We put almost 1,000 miles on it since and got the codes for oxygen sensors.
I replaced all 4 oxygen sensors and had the codes for them reset. On the way home the car died and wouldn’t start. It cranked over and smelled flooded. I let it sit about 5 minutes and it started after several attempts, struggled to idle and kept dying, and eventually seemed to cleared up and run ok. I stopped at the parts house and they pulled the below codes. It started normally and drove home fine. The next day it started normally but didn’t make it out of the driveway. That was the last time we got it to run.
The week prior it would sporadically idle up to 1200 and down to about 700 at different times, and occasionally felt like it lost all power (like the spark shut off) for a second and then would recover.
If you don’t think it’s the opti spark please let me know. We didn’t do much trouble shooting as it seemed like an obvious opti spark from what I read.
P0372- Timing Reference High Resolution Signal 'A' Too Few Pulses
P1371- loss of PCM communication/ loss of low resolution pulse from optical cam position sensor
P0140- rear 02 again (just replaced it)
I pulled the whole hub off. I didn’t think I could get the opti off without doing it that way. Just to confirm, it doesn’t matter the orientation that I put the hub back on the crank as long as I press it all the way on??
Last edited by shipsandefur; Mar 14, 2025 at 02:28 AM.
The need to align the hub is debated. Some feel the little balancer weights in the holes on the pulley/damper were installed to balance the pulley/damper. Others feel they were put there to fine tune the engine crank balance. The only time I changed the hub was when I installed an early version of an aftermarket system that deleted the Opti - Electromotive SDI/Opti Eliminator. The system required adding a 60-tooth crank wheel on the face of the pulley/damper. Added a timing marker, allowed initial timing to be set with a timing light. I bought a keyed hub, because that system had to be prevented from slipping. PS: The Electromotive was a dud.
I would play it safe and follow the factory service manual. You can download a free copy here:
On page 6A3A-13 it recommends a method to reinstall the hub if no reference marks were made before it was pulled.
The crankshaft hub can be installed by a different procedure if the engine should accidentally be cranked over after match marking the hub and engine front cover. A. Set number 1 piston to top dead center. B. Install crankshaft hub with cast arrow on hub in the 12 o'clock position.
I would recommend you look at the brief hub install advice on Shoebox's site (25 years as the top source of LT1 info).
You're probably OK on the Opti being the problem. I would recommend a quick check of the harness connectors - both the grey connector on the bracket on the passenger side of the intake manifold, and the connector at the Opti (if not an aftermarket direct wired unit). The connector at the Opti can grow some white/green corrosion.
The part dealing with the "Optispark Harness" checks the PCM side of the system, to make sure the PCM is supplying 12 volts to power the Optical module, a ground, and the two 5 volt reference voltage that the high and low resolution pulse signals ride on.
