Opti-Spark?
 

How can you tell if your Opti-Spark needs to be replaced on the LT-1? Did all years have that problem and does the LT-4 Engine have the same system? Thanks

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RE: Opti-Spark?
 

Well for starters it will throw codes. Why are you asking?Yes the LT4 has the same system. My 92 has 140000 miles on the original opti. Don't be too quick to condemn the opti. Usually the car will stall and won't restart when it fails.

The OptiSpark (Opti) was introduced in 1991, with the LT1 as part of the 1992 model year.

The Opti is made up of two sides, one side, the side against the engine, is an optical pickup. The pickup is made by Mitsubishi, and is a very reliable component. The optical system reads a disc that has marks in it. On the outer edge are 360 marks, inside that, are four marks. The outer marks create the so called "High Resolution" signal to control timing, the inner marks, or "Low Resolution" are used to signal fuel delivery.

A common shaft joins the optical side with the high voltage side. The high voltage side is similar to any distributor, except it is much thinner. The unique part, the sides of the cap are sequenced, so all the odds are on one side, evens on the other!

In 1995, the second generation of the Opti was released. It has a venting hose and is better constructed.

Codes can present themselves if an Opti is failing. These codes very by year, but for the earlier versions, codes 16 and 36 are bad(Note: these codes only apply to 1992 - 1995, 1996 uses ODBII and has different codes). This means the optical portion has a problem. Most likely, the error is caused not so much a failure in the optical portion, but the bearings having worn out, causing a wobble in the drive shaft.

A common problem is when coolant from a bad waterpump leaks in. Coolant will eat the grease inside the sealed bearings. This causes the common shaft to wobble.

If there is a wondering idle or a high RPM miss, you can blame a bad cap/rotor. The cap/rotor fails due to carbon tracing, caused by moisture getting into the Opti.
New Optis are available from the dealer. Also available is the Venting Hose Kit, that can be retrofitted to the original cap design.

You can also update an earlier engine to the later Opti, by changing the timing cover and various internal parts related to the timing gear.

I cannot advise a cap/rotor change. The labour is the same... and there is no guarentee that a rotor change will result in a long term repair.

If your car is a 1995 or newer, then a cap/rotor change might just be worth investigating.

Regardless of the vintage, removing the cap and sealing with RTV is a good idea. It might not be a bad idea to install a drain hose on the waterpump, to direct the weap holes output to the side, instead of on the Opti.

I do not recommend the Ecklers or Mid-America cap venting system. It is a single hose, and as such does not create positive pressure. It might suck some stuff out, but I just don't see how it can without creating a complete loop.

Aftermarket Options

There are now a few options available:

[ul][*]Dyna-Tech - This is a totally reengineered version of the Opti. A good idea for those who wish to maintain a stock look.[/ul]
[ul][*]LTCC - This uses eight LS1 coils, and the Opti to read the data needed to fire the coils.[/ul]
[ul][*]DelTeq - This is similar to the LTCC, but uses a Northstar coil pack.[/ul]

Generic replacement Optis are not recommended. They don't include the cap/rotor and are of questionable reliability.

RE: Opti-Spark?
 

Lee, Is it possible to replace the cap and rotor on a 95 Opti without draining the coolant and removing the water pump? I have all the tune up parts but really don't look forward to draining all that coolant again if I don't have to. Thanks

RE: Opti-Spark?
 

You have to remove the water pump. [:o]

RE: Opti-Spark?
 

Mech is correct.....as usual.:D

RE: Opti-Spark?
 

Copy that Mech, Kinda sucks because I just did the whole coolant thing last summer. Thanks.

RE: Opti-Spark?
 

Does any one know where I can find an article describing this operation? Like everything needed, time it should take, tools needed, etc. Thanks again

RE: Opti-Spark?
 

Here is an article, pertains to 92-94 but the idea is the same for cap and rotor replacement, you just don't need to makeany modifications to the opti-spark unit. http://www.corvettefever.com/howto/16758/

RE: Opti-Spark?
 

Get a Factory Service Manual, and follow the procedure it lays out.

Here are a few tips. This is from a friend and I believe this is pretty complete. I am sorry there are no pics to go along with this.

Drain the cooling system.

Disconnect the MAF sensor and remove the air intake duct with the MAF.

Disconnect the ECT sensor and remove it from the water pump.

Remove the serpentine belt and tensioner.

Unbolt the coil/ICM bracket from the right cylinder head.

Unbolt (but don't remove) the power steering pump. This will help you to sneak the new plug wires in/out behind the pump, but may also be somewhat helpful when working on the water pump/Opti.

If you want more room to work, you can remove the radiator, but it isn't strictly necessary.

The FSM will tell you that you need a special Kent-Moore puller to remove the crank pulley/damper. You don't. Here's how to get it off:

1. Raise the front of the vehicle enough that you can get under the car (it's also helpful to have it at a more comfortable height while you're working from above).

2. Remove the three bolts that secure the pulley/damper to the hub.

3. Mark the damper and hub so that you can easily see how to realign them to each other later.

4. Slide under the car with a long pry bar or hardwood dowel (I use a jumbo Snap-On screwdriver that's around two feet long) and a mallet.

5. Place the tip of the pry bar against the rear face of the damper, as close to the hub as possible (Ideally rest the tip alongside of the hub).

6 Give the pry bar a few whacks with the mallet, and with any luck the damper will pop off without too much of a fight.

You may find it helpful to apply a few whacks, then rotate the crankshaft in 120* increments, whacking it a few times at each interval (I haven't needed to do this).

It's also helpful to, if possible, shoot a bit of penetrating oil where the damper meets the hub, a day or more in advance of doing the job.

After you get the damper off, clean the damper/hub mating surfaces to remove all corrosion, etc, and apply a very thin coating of anti-sieze compound to these surfaces before you reassmble the damper to the hub. This should make it a lot easier to get the damper off next time.

Once the damper is removed, rotate the crankshaft so that one wing of the damper hub is at the six-o'clock position. This will position the other two wings at around the ten- and two-o'clock positions. In this orientation, the Opti will clear the hub as it is being removed/installed.

The Opti basically unbolts and pulls off as you'd expect, once you have the water pump and damper out of the way.

Once the Opti is out of the way, inspect the shaft seals for the Opti, water pump, and crankshaft. If they show any signs of leakage, replace them now.

When you install the new Opti, be sure to align it correctly with the cam gear, and don't force it into place against the timing cover (do NOT use the bolts to draw it into place). At most, give it a gentle bump with the heel of your hand to encourage it to pop into place.

When you're installing the new water pump, if it doesn't slip right into place against the front of the engine block, the splined drive shaft is probably not perfectly aligned with the splined input of the water pump. If this happens, pull the pump back off and turn the input shaft in the pump a few degrees, and try it again. Repeat as necessary until it slips cleanly and easily into place.

Follow the cooling system refill procedure in the FSM carefully, and you'll have no problems with this. In particular, be sure to bleed the air out of the system as it's being refilled.

Plugs & Wires:

Changing the plug wires on an LT1 is not a lot of fun, but it can be done. Here are a few tips:

1. Raise the front end of the vehicle to a more comfortable working height.

2. Remove the inner fenderwell center panel on the driver's side. This will allow you to both see and do the job much more easily on the driver's side. You may also find it helpful to remove the wheel.

3. Unbolt the ASR bracketry from the frame, so that you can slide the ASR unit around to get it out of your way.

4. Unbolt the power steering pump so that you can move it forward around a half inch. This will make it much easier to sneak the plug wires in/out behind the pump.

5. Remove the serpentine belt and tensioner.

6. Use dielectric grease in the boots at both ends of the wires. Be sure to "burp" the air out of the boots after you get each of them pushed firmly into place, so that the trapped air doesn't try to push the wires off later.

Some guys report that they've had decent success accessing the Opti-end of the plug wires from underneath of the car. I haven't tried this, so I can't comment.

Take your time, work with care, and pay attention to what you're doing. The OEM replacement plug wires from your Chevy dealer are high quality parts, and will route (and fit into the wire looms) correctly. Run the new wires properly, and make sure they stay away from anything that moves, is sharp, or gets hot.

The passenger's side is not such a bad job. The driver's side is a Queen Royal Beyotch. With plenty of patience, beer and Band-Aids, you'll get it done.

The spark plugs on the driver's side aren't so bad, when you've got things apart to do the wires. The passenger's side, however, is not so easy. The number 8 plug in particular can be a real headache, but with good tools and enough patience, you can get it done. I use a spark plug socket that has a hex head on it so that it can be turned with an open end or box end wrench. It's useful to have more than one plug socket to choose from, as some will work better than others due to differences in length, wall thickness, etc.

Be sure to apply a small amount of anti-sieze compound to the threads of the new plugs before you install them. Just make sure none of the compound gets onto the electrodes or insulator of the plugs.

RE: Opti-Spark?
 

Lee thanks a mill buddy, Thats exactly the guidance I needed, I'm half way through the job now. Just checked in to see if I could find out how to get that front hub off. Thanks again! Back to the garage, Oh is there any type of timing I have to line up on the new cap? I'll check back later for a response Thanks.