Stop Replacing Opti's!!!!
10-30-2014, 01:26 AM
#1
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Thread Starter
Stop Replacing Opti's!!!! O.k. I'm starting this thread in the hopes that we can get all us LT1 guys to understand what the Optispark does and when to replace it.
Too often the Optispark is replaced when it's not the problem. This leads to a lot of negativity about it and people replacing a good Optispark and not solving their issue.
Please correct any information that follows if it is incorrect. And please feel free to add anything relevant. Like details about the 6AL and it's effects on the Optispark...
The Optispark is the LT1's Camshaft and Crankshaft Position sensor AND it's distributor. It is mounted to the front of the cam and spins 1:1 with it. The Optical sensor sends pulse signals to the PCM and tells it when each cylinder is in a certain position. The PCM then takes that signal and sends out the pulses to the ICM for spark timing and the injectors for injector timing. Clarification, the PCM controls spark timing and sends the signal to the ICM.
This is important to note. The LT1 is a equipped, from the factory, with a fuel injection system (batch injection 92-93, sequential multi port injection 94+; this means that the injectors are timed to inject fuel only during the intake stroke of each cylinder).
If the actual Optispark fails the injectors AND the spark will not work because the PCM doesn't know at what position the crank is at and therefore cannot time either event. They both use the same sensor to time their events.
So next time you have a spark issue, check your injectors BEFORE you replace the Optispark assembly. If they are still pulsing then your issue is likely somewhere else.
The best way to test the Optispark is with an Oscilloscope. But, many of us don't have one and probably never will.
That being said, if the injectors are pulsing it doesn't mean that they are pulsing when they should. It only means the Optical sensor is still working. Many times, if the timing is off, it's because the sensor is dirty (typically from a leaking seal) and all that is required is a good cleaning, resealing, and re-installation of the same unit. USE LOCTITE or RTV!
One of the most common things I've noticed is people replacing the whole unit when all they need is the Cap and Rotor. Because the Optispark is a distributor too the cap and rotor require periodic replacement (like any other distributor system).
When replacing the Cap and Rotor it would be a good time to replace the timing cover seals and clean the Optical sensor too. Don't forget to seal the unit up too- very important. Also check to see if it's got the Mitsubishi sensor, if so and if it was working, keep it. Don't replace the whole unit just because it is old. Many times the newer unit has parts that are of far less quality; especially the none Delco/Delphi units from the local parts store.
Another issue is people mounting aftermarket stuff to the Optispark system. Because the distributor is part of the Optical sensor housing it causes ozone in the unit (this is why GM revised the unit to be vented). The ozone is very not good for the Optical sensor. The stronger the spark going through the distributor the more damage it does to the Optical sensor with every pulse sent. It's best to use the stock coil with the Optispark distributor and ensure the venting system is properly maintained. Many people have gone 200+K miles using the stock GM set up, others have gone into the 9's. It's a very capable system.
Too often the Optispark is replaced when it's not the problem. This leads to a lot of negativity about it and people replacing a good Optispark and not solving their issue.
Please correct any information that follows if it is incorrect. And please feel free to add anything relevant. Like details about the 6AL and it's effects on the Optispark...
The Optispark is the LT1's Camshaft and Crankshaft Position sensor AND it's distributor. It is mounted to the front of the cam and spins 1:1 with it. The Optical sensor sends pulse signals to the PCM and tells it when each cylinder is in a certain position. The PCM then takes that signal and sends out the pulses to the ICM for spark timing and the injectors for injector timing. Clarification, the PCM controls spark timing and sends the signal to the ICM.
This is important to note. The LT1 is a equipped, from the factory, with a fuel injection system (batch injection 92-93, sequential multi port injection 94+; this means that the injectors are timed to inject fuel only during the intake stroke of each cylinder).
If the actual Optispark fails the injectors AND the spark will not work because the PCM doesn't know at what position the crank is at and therefore cannot time either event. They both use the same sensor to time their events.
So next time you have a spark issue, check your injectors BEFORE you replace the Optispark assembly. If they are still pulsing then your issue is likely somewhere else.
The best way to test the Optispark is with an Oscilloscope. But, many of us don't have one and probably never will.
That being said, if the injectors are pulsing it doesn't mean that they are pulsing when they should. It only means the Optical sensor is still working. Many times, if the timing is off, it's because the sensor is dirty (typically from a leaking seal) and all that is required is a good cleaning, resealing, and re-installation of the same unit. USE LOCTITE or RTV!
One of the most common things I've noticed is people replacing the whole unit when all they need is the Cap and Rotor. Because the Optispark is a distributor too the cap and rotor require periodic replacement (like any other distributor system).
When replacing the Cap and Rotor it would be a good time to replace the timing cover seals and clean the Optical sensor too. Don't forget to seal the unit up too- very important. Also check to see if it's got the Mitsubishi sensor, if so and if it was working, keep it. Don't replace the whole unit just because it is old. Many times the newer unit has parts that are of far less quality; especially the none Delco/Delphi units from the local parts store.
Another issue is people mounting aftermarket stuff to the Optispark system. Because the distributor is part of the Optical sensor housing it causes ozone in the unit (this is why GM revised the unit to be vented). The ozone is very not good for the Optical sensor. The stronger the spark going through the distributor the more damage it does to the Optical sensor with every pulse sent. It's best to use the stock coil with the Optispark distributor and ensure the venting system is properly maintained. Many people have gone 200+K miles using the stock GM set up, others have gone into the 9's. It's a very capable system.
Last edited by hrcslam; 11-06-2014 at 09:04 AM.
11-02-2014, 02:08 AM
#4
TECH Addict
Thread Starter
Recently my machinist told me that the cheap Opti's have been pressed together wrong causing the timing disc to be more than a few degrees off from where they should be. This recently caused havoc on one of his customers 383 (3 cheap Cardone Opti's in a row!). They bought a Delphi and problems were solved.
11-02-2014, 03:15 AM
#7
TECH Addict
Thread Starter
Off topic: Did you build your 8.8? Do you have a build thread? I'd like to see how you trued the axle tubes before welding.
Blinkers blinking to fast, Opti!
Low Coolant light it on, Opti!
Wipers don't work, Opti!
Cruise Control inop. Opti!
Window regulators failed, Opti!
The light at the intersection turned Yellow, Opti!
Now the light is red, Opti!
Flat tire? It's the Opti!
ARGHH!!ADHGRHAGDHSHA!!!!!
/Rant.
Last edited by hrcslam; 11-27-2014 at 10:19 AM.
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11-02-2014, 03:57 AM
#9
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Thread Starter
11-02-2014, 08:22 AM
#10
TECH Veteran
Diagnostic/operation info for the opti has been out there a long time. People just choose to ignore it (and they will continue to do so). Regardless of your intentions with this thread, you'll still see more opti threads. I guess it does not hurt to try, though.
11-02-2014, 08:25 AM
#11
As time marches on and less parts providers care to cater to the LT1 crowd, replacement opti units will become worse. In time, the only viable opti unit will be the MSD unit.
11-02-2014, 08:36 AM
#12
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Please elaborate on the MSD limiting factors... Im curious. When I sent mine in to be rebuilt, they said it was tested to 7000 rpm. What part of the MSD opti design is limiting?
11-03-2014, 08:11 AM
#16
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This guys at about 400rwhp at 3K rpms (I thinks he's E85 and 14:1 or something along those lines), he's had a lot of issues with his MSD Opti. He finally went 24x.
11-03-2014, 09:22 AM
#17
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Thread Starter
This is good information. I know with a Delphi/Delco unit it's a one time big purchase. MSD is almost as reliable (if not just as) and they are rebuildable, making them cost less in the long run.
11-03-2014, 11:06 AM
#20
While that video was painful to watch, it was informational.
24X is a cure to the opti issues...if it in fact opti is the issue or if you spin the motor to the moon. BUT at the price for a 24x conversion, I'll pass since I have no need to spin my car past OEM redline along with my opti is not giving me issues.
24X is a cure to the opti issues...if it in fact opti is the issue or if you spin the motor to the moon. BUT at the price for a 24x conversion, I'll pass since I have no need to spin my car past OEM redline along with my opti is not giving me issues.