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Optispark replacement

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Old 08-11-2018, 08:47 AM
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Optispark replacement

I recently started to replace my optispark and came across an issue. I bought a vented MSD optispark and when i pulled the old one off the splined shaft is still attached to the camshaft behind the timing cover. The back of the MSD has a splined shaft coming out and into the timing cover. I have an idea what i have to do but i could use some advice on this. Every part i look up says 2 types of optis. Splined or pin. Heres a pic. Any help would be awesome.

Front timing cover 93z28

Last edited by importkiller69; 08-11-2018 at 08:50 AM. Reason: Spelling
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Old 08-11-2018, 10:46 AM
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Re: Optispark replacement

Background:

93/94 factory Opti is unvented, and uses the splined shaft drive

http://shbox.com/1/93-94_opti.jpg


95-97 factory Opti is vented and uses the cam dowel pin drive

http://shbox.com/1/opti_back.jpg


All MSD Optis are vented, but drive mechanism has to match the year of the engine in the car.

While there is a “shaft” in the center of a 95-97 Opti, it is not splined. It is a pilot shaft that rests in a chamfered hole in the end of the cam.

When you removed the Opti, the splined shaft should have pulled out with the Opti, but if it’s the original 25-year old Opti, the shaft could be “stuck”. All you need to do is pull the splined shaft out of the cam sprocket.

Two cautions:

- look carefully at Shoebox’s photo of the 93/94 Opti. There is an “odd” tooth that has to be aligned exactly with the matching slot in the cam sprocket splines, or your timing will be off.

- unfortunately, the MSD has a few design problems, and is not reliable. A rebuilt AC Delco or a Delphi would be a better choice. They are getting hard to find. The unit sold by Petris seems to be the most promising replacement at this point..... very popular with Corvette LT1 owners.
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Old 08-11-2018, 11:28 AM
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Re: Optispark replacement

Originally Posted by Injuneer View Post
Background:

93/94 factory Opti is unvented, and uses the splined shaft drive

http://shbox.com/1/93-94_opti.jpg


95-97 factory Opti is vented and uses the cam dowel pin drive

http://shbox.com/1/opti_back.jpg


All MSD Optis are vented, but drive mechanism has to match the year of the engine in the car.

While there is a “shaft” in the center of a 95-97 Opti, it is not splined. It is a pilot shaft that rests in a chamfered hole in the end of the cam.

When you removed the Opti, the splined shaft should have pulled out with the Opti, but if it’s the original 25-year old Opti, the shaft could be “stuck”. All you need to do is pull the splined shaft out of the cam sprocket.

Two cautions:

- look carefully at Shoebox’s photo of the 93/94 Opti. There is an “odd” tooth that has to be aligned exactly with the matching slot in the cam sprocket splines, or your timing will be off.

- unfortunately, the MSD has a few design problems, and is not reliable. A rebuilt AC Delco or a Delphi would be a better choice. They are getting hard to find. The unit sold by Petris seems to be the most promising replacement at this point..... very popular with Corvette LT1 owners.
thank you
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Old 08-11-2018, 12:48 PM
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Re: Optispark replacement

Thank you. So what if i didnt pay attention where the rotor position when i removed the optispark. Since the the msd opti have has no key way. I have seen posts on the incorrect installation on the opti. Is there a past post that you know of that i can reference
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Old 08-11-2018, 04:57 PM
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Re: Optispark replacement

While I don't have any experience with the MSD cap and rotor, it should only go on 1 way. Can you snap some pics?.

When reinstalling the Opti make sure you line up the splined shaft up correctly. It should fit tight to the block without excessive force, or drawing it in with the opti bolts. Take your time with this, as there have been many posts about cars not running right after an opti install. They all start out as "I am 100% positive I lined the opti up correctly" Only to find out through a long trouble shooting process, that they in fact, didn't have it aligned properly.

One more thing to take your time with, is the placement of plug wires, that is another thing people swear they put them back "exactly" as I took them off, only to find out they were installed wrong.

Last edited by Pullngz; 08-12-2018 at 05:00 AM.
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Old 08-11-2018, 10:30 PM
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Re: Optispark replacement

You need to clarify.... does the back of your MSD Opti match Shoebox's photo of the 93/94 unit, or the 95-97 unit?

Your initial post said the MSD has a splined driveshaft. If it has the splines, one of the splines is different than all the others (the one Shoebox calls the “key”). Look at the photo. If your MSD Opti does not have that “different tooth, it is defective. Send it back and get a better Opti.

Look at the corresponding “slot” in the cam gear. The tooth Shoebox calls the “key” has to go into that slot. If you get the key in the slot, that's what matters. You don't have to remember where the rotor was. In theory it will only go together that way. Many people somehow manage to screw that up. I suspect they get it aligned incorrectly, the Opti won't bottom out on the front of the engine, so they torque the bolts down, forcing the splines to mesh incorrectly.

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