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Thread: Optispark

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    Default Optispark

    Can anybody recommend a good lower cost Optispark for a 96 LT4?

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    I am seeking a reliable Optispark for my 96 LT4 Corvette. Can anyone recommend one of the lower-cost units as being reliable ?

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    Moving out of the Site Help and Feedback forum and into the correct C4 Tech forum....


    Rob Loszewski, Owner & Site Administrator
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    Default Ted's Opti Experience C4 '95

    Quote Originally Posted by Scubaman View Post
    I am seeking a reliable Optispark for my 96 LT4 Corvette. Can anyone recommend one of the lower-cost units as being reliable ?
    I just replaced the opti on my 95 C4. I don't have the mfg. right now but my bro, an ANSI mechanic who owns his own shop, will get me that info today and I will let you know. In the meantime, here are some comments based on the 4 opti's I have either used with success, or tried to use without success.

    1. When changing out opti, CHANGE THE WATER PUMP, even if it's only a couple of years old.
    2. Unless you have done so in the last 5-10 years, also change out the water pump and opti drive seals (located in the timing chain cover; the water pump shaft-to-timing cover seal gets tricky, and if you roll the seal you will end up with a nasty oil leak. Change the leals cause after many years these will have turned hard and will be worn to the point of oil leakage/seepage.
    3. Test the opti before install to make sure it pulls a vacuum. If it does not send it back! If you do not know the reason for this vacuum, or you want to know how to test, then respond back.
    4. If you buy an MSD (not a bad opti, but pricey) make sure the mounting surface is IDENTICAL to the mounting surface of your old opti. Compare very carefully. I tried two diff. MSD's for my '95 and neither would fit due to the way the rear of the opti was designed. I even sent MSD a photo of what the offending object was on their opti that prevented it from sitting flush on my timing chain cover and they were truly stumped. PN was verified as correct by them.
    5. GM opti's, as you prob. know, are pricey but they seem to work as well as any other mfg. I've tried, but I have been through 4 of them in 67,000 miles now, but you can tell my C4 does not get a lot of road miles so that may cause the opti seals to degrade faster than if they are constantly in use (ie-lubricated).
    6. Once installed, you may want to check the weep hole on your water pump at least a few times per year to make sure it is not leaking. Pump leaks will kill your opti faster than anything I know. Yes, even faster than an engine pressure wash, because antifreeze is not kind to internal components of the opti, given the heat and tremendous normal transfer of 40k volts, or more, between the rotor and the spark plug take-offs.
    7. IMHO, opti repair kits are worthless because they do not include a new rotor seal, which are main culprits for oil intrusion and vaporization inside the opti, but if you go this route make sure to use locking goop on the screws that attach the rotor to its base.

    Hope this helps for now. PS- I added my own title above so I can easily find my post to respond to any other questions you might have.
    Ted

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    Thank you so much! Could you plz explain how to pretest the opti to be sure it pulls vacuum? Much appreciated!!

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    Also, do you see any issue in pressure washing the engine before I install the new opti? Itís quite a mess in the front part of the engine. Tks!

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    Quote Originally Posted by Scubaman View Post
    Also, do you see any issue in pressure washing the engine before I install the new opti? Itís quite a mess in the front part of the engine. Tks!
    1. Regarding vacuum testing the opti, you will notice two orifices on the opti, other than the 8 spark plug terminals. One of the orifices should be brass or aluminum and the other is molded plastic as part of the opti mold. The brass orifice is used to draw vacuum through the attached hose, through a small blue/white one-way check valve disk then through a larger blue/white filtering disk and finally to a vacuum fitting protruding out of the front of the intake manifold. The other molded-in, larger orifice has a tube attached that runs directly to an L-fitting on the ribbed, neoprene intake tube in which the MAF sensor is located. The fitting on the intake manifold draws air through the opti. The intake air to the opti comes from the filtered air just aft of the MAF via that small L-fitting. This action effectively draws fresh air into the opti and into the intake manifold to keep the opti internals nice and dry. If this vacuum draw is compromised through a leak in one of the fittings, one of the hoses, or through one of the opti seals, then moisture will not be removed. It is especially important that air is continuously drawn through the opti, in case of water intrusion or antifreeze intrusion from a leaking water pump rear seal. TO TEST THE OPTI OFF THE CAR: Simply cover one of the two orifices with your finger, while applying suction with your mouth to the other orifice. See if you reach a point, fairly quickly, where you can no longer suck air. If so then your opti is well-sealed. Of course you can always use a hand-held mechanical vacuum pump to do the same test. If you keep sucking air then the opti has crappy seals and should not be used. 2 out of 3 opti's I tested including a cheap Chinese eBay opti and even the MSD opti (regardless of it not even fitting correctly) were leaky. TO TEST THE OPTI ON THE CAR (engine off): Simply remove the L-fitting hose from the MAP intake hose. Pinch off the hose coming from the intake manifold. Apply vacuum with mouth or with vacuum pump. If opti seals are not leaking you should see a few pounds of vacuum slowly build up and hold on the gauge. If by mouth, then very quickly you will be prevented from applying further vacuum.
    2. To answer your other question, several C4 owners swear that lightly power washing the C4 engines with optis does no harm, providing you go easy around alternator, opti, and any other old electrical connections. You do run a slight chance, however, of getting water into older, dried out neoprene gaskets protecting your electrical connections, thereby taking you hours and maybe days of waiting for that water to evaporate so your engine systems will operate as intended. Your engine may not even start if components in your ignition system get wet. At worse case, one of your many terminals may short out, leaving you a huge headache trying to find out what all this short-circuit ruined. Me? I just use a cleaner spray like 409, Goo Gone, Simple Green, etc., followed by judicious use of many small rags and perhaps a shot or two from my air compressor for those hard to reach areas.

    PS- I am still waiting for my bro to call me with the Opti mfg. that I last used. I do have his receipt for $149 (wholesale), including tax, but not the mfg. Still working on that. Keep in mind however that the opti is the heart of your ignition system and you really should not skimp on quality here. Really, you can't go wrong with a new or factory reman. GM opti, but you are going to pay for that peace of mind. Watch often for weeping antifreeze from the water pump and correct as necessary and your opti should last for many thousands of miles.

    Good luck with this. If you attempt a DIY water pump and opti replacement I'll be around to lend you some advice.
    Ted

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    Spectra Premium Industries is where my brother got my reasonably inexpensive opti. High quality for the price. I'd be interested in knowing how this works out for you.

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    My understanding was that the 96 Opti was finally vented effectively and was supposed to correct reliability issues? Of coarse if the seals are old/dried or worn that means nothing...

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    Quote Originally Posted by LT4 View Post
    My understanding was that the 96 Opti was finally vented effectively and was supposed to correct reliability issues? Of coarse if the seals are old/dried or worn that means nothing...
    Actually that effective venting began in 94-95 and carried over to the last C4 production in 96. Someone correct me if you know otherwise.
    Ted

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    Thank you very much Ted for all your advice & assistance! Iím about to contact Spectra Premium Re: Optiówondering if your brotherís is still working ok? Thanks again!

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    Quote Originally Posted by Scubaman View Post
    Thank you very much Ted for all your advice & assistance! Iím about to contact Spectra Premium Re: Optiówondering if your brotherís is still working ok? Thanks again!
    My wife and I just completed a 2000 mile round trip in the C4 and the optispark was absolutely flawless. It is also still drawing a good vacuum as many others I tried did not, as you know.
    Ted

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    Great! Thatís the one Iím going to order.

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    Hi Ted; I ordered the new Spectra Opti, should have it by Friday. As well as vacuum testing it, do you suggest I test the electrical output on it it by plugging it into the carís electrical, also hooking up a spark plug to a plug wire, turning the carís ignition to on, and then spinning the new opti with a drill, grounding the plug to cast manifold, & watching the sort of spark the new opti produces before going to all the work of installing it on the car only to find out itís defective?

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