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Discussion Starter · #1 ·
I have read quite a lot about problems with water getting inside the LT1 distributor and of course, wiping out all the internals. GM even modified it later to add a vacuum hose to "suck" out any moisture. I'm not the smartest but why hasn't someone tried sealing the outer case with silicone, rtv, etc., to prevent water or moisture from getting in? I presume the little O-ring supplied with the cover doesn't work very well or there would not be a problem with moisture. Seems to me if the case were properly sealed, then you could put the distributor in a bucket of water and not worry about the internals getting ruined. Has anyone experimented with this problem with any success? I am installing an LT1 in my '55 Belair which will be a daily driver and would appreciate any help with this issue as I just love to wash the engine to keep it clean. Thanks, :)
 

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I don't know how water resistant the 95 up Optispark units are, but from what I understand, if the shaft seal on the water pump goes, and eventually it will, the Opti is a dead player or soon will be too. I think the vacuum setup just keeps humidity from being a problem, not liquid water or coolant.

So the usual recommendation is if you pull the pump and replace the Opti unit, you replace the pump too. Likewise if the pump starts leaking, just replace both or you'll be back in there doing it again.

A bad Opti unit is the most likely reason for an LT1 engine to run badly.

I've never heard of a home shop procedure that would seal up one of these sufficiently to call it water resistant (nothing is "waterproof"). I'm of the opinion you're wasting your time.

And if you're doing a swap, water pump seals are notorious for going away while sitting dry. So unless you get your donor and get it running quickly, the best advice is to just replace the Opti and the water pump as part of the swap. That's what I'm doing.

Also, there is supposed to be a huge difference between the genuine GM replacements and the "rebuilt" replacements you can get at the auto supply. MSD came out with new units a few years back and they were junk, I don't know if they made them better since then or not. List price on an Optispark from a dealer will make you faint. Definitely shop around. I picked up a new 95 up Opti off Ebay from a Chevy dealer for less than 50% of list. Prices vary a lot.
 

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Discussion Starter · #3 ·
I guess not too many people know about these distributors. By the way, anything can be made totally waterproof with the right tools. How did they ever make underwater cameras? Why didn't GM design a decent O-ring or something to prevent water from getting inside the distributor especially when it sits under the water pump? They knew the pump would eventually leak. Maybe that's why they sell so many aftermarket parts. :eek:
 

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Trust me, I make my living at designing and building things that are used underwater, and there is no such thing as waterproof. Just degrees of water resistant.

The trouble with completely sealing a distributor cap is that operation produces ionized gases which are conductive. This will cause crossfire in the cap. A static vent wasn't enough for the Opti cap, so they went to the flow through design with the hoses connected to it to carry the ionized gases away.

So they had contradicting problems. Solve one, make the other worse.

These same ionized gases are why you see all the corrosion on the weights and springs on an HEI unit.

The best design solution for the LT1 would have been to put the distributor somewhere else, or do what they did on the LS1 - go to a distributorless system.
 

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An LSX type ign is available...NOT CHEAP!
 

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You're right, I can buy several GM Opti units and water pumps and not spend as much.

And to my way of thinking there's nothing wrong with a fresh Opti - even though there's nothing worse than a malfunctioning one.
 

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Had to replace the Opticrap on my wifes 96 T/A. Not fun. and the water pump was also replaced while I was there. I researched it quite extensively beforehand. Ended up adding a MSD 6AL, adapter harness and MSD coil which made it run much better.

If I was to do it all over again,,I wouldn't. A few folks out there have adapted a jesel belt drive dist to LT1's.
 

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I put a carb intake on my LT1, and put a regular dis in it and welded a 1/4" plate where the original one went.. works wonderful.
 
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