Oldtires

Hello to all. I have a 1993 LT1 , One quick question , Has anybody used a 12 volt air pump to pressurize the opti spark ? this way it gets fresh air and keeps all contaminates out . Positive pressure hose to the Opti and Vacuum hose side from the Air filter case. Just have to find a live 12 volt after the switch. ( any suggestions ? ) Thanks Here is a link to the pump i might try. https://www.ebay.com/i/163050831142?chn=ps

Kevova

I haven't tried to put a gen 2 cap on a gen 1 opti. I saw someone modified a gen 1 cap by drilling vent holes and connecting it like a gen 2. After cap is vented I don't know there will be an advantage to the air pump.

Whaleman

The gen 2 vented work just like an air pump using engine vacuum. Gen 1 can be modified and should be. Dan

SJW

Agreed. The actively-vented, Gen 2 units were a big improvement over the Gen 1 units. There's no need to use an air pump, or re-invent the system in order to accomplish what GM already figured out when they used manifold vacuum to purge moisture and corrosive ozone from the Gen 2 opti. Just do as they did, and be sure to do it right. Tap the inlet air from aft of the MAF so that you're not introducing un-metered air into the intake, remember to include a check valve between the manifold and distributor, and route the vacuum lines carefully so that they don't get crushed or abraded by sharp or moving parts. It's really not complicated.

Live well,

SJW

Oldtires

So will go with the 2nd gen. vac design. I guess just make sure to seal the distributor vac tight. I drive everyday rain, sun, snow , bring it on . Thanks

SJW

Be aware that you can't bolt a Gen 2 unit onto your engine. The camshaft drive coupling arrangement is different. You can, however, add the Gen 2 active venting to your Gen 1 distributor. Search the archives here for posts about how that's done.

Live well,

SJW

jvettman

Oldtires

I rebuilt my Opti spark and installed the Vac system , WoW what a difference . much nicer on slow pedal control. The main Question to this post was has anyone done the positive pressure on the Opti. and the Answer is nobody has . Thanks Y'all back to the Shadows i go.

mixalive

https://www.corvetteforum.com/forums...tallation.html
Check out this thread concerned with vacuum checking your optispark for air leaks.

cardo0

Haven't done it but considered using a 12v aquarium pump mainly because I'm suspicious of the vacuum system drawing in contaminates (like water) through the cap and housing seals. A positive pressure system should be cleaner and provide air continuously regardless of engine vacuum.
But I have met a former LT1/opti owner that used a small CO2 cartridge on his Opti. Said it worked great for him but I don't see how a small cartridge could last very long. Well as far as that goes any positive pressure system would be an experiment as air pump life would always be in question.

Good luck and please let us know if you find something that works.

Tom400CFI

All of the air in that system is filtered by the air filter. Only way you're getting contaminates or water in there is if your air filter is removed and you're going deep river fording.

cardo0

Read someone crapped up their Opti with a deluge from the radiator hose. But probably BS as usual.

Tom400CFI

Someone did. What's that got to do with the venting systems that we're discussing in this thread?

More BS as usual is right. YOU said:
"I'm suspicious of the vacuum system drawing in contaminates (like water)"

I replied and said that on the vented system, all the air used for the venting is filtered air. Meaning; how ya gonna get water and contaminates in there?

So now....what are ya doin' Cardo? You're arguing just to argue again. Just like you always do. The type of system you choose for venting's got nothing to do with dumping water on the opti from a blown hose. IDK why you brought that up, other than to argue again. The factory system uses filtered air specifically so it doesn't get contaminates into it. IOW, "engineering" your own fish pump system is pointless for the reasons you listed (contamination) and won't accomplish anything that the factory system doesn't already accomplish.

cardo0

It takes you 4 paragraphs to tell us your butt hurts. And we can read you don't understand how a positive pressure system can work.

Have you found pyschological help yet?

Tom400CFI

Hey Cardoooo, That's OK with the insults. I "get it"....it's what people do when they're wrong, can't admit it and don't have the maturity to handle it better. Best of luck to you and you fish-tank-opti.

MatthewMiller

A vented opti with vacuum drawing in fresh air is never under significant negative pressure inside the cap. The point is to move fresh air through the system, not to pull a vacuum (i.e. pressure differential) on it. The opti internals are wide open to the atmosphere via the fresh-air supply tube that connects to the intake snorkel. Therefore, the vacuum moves air through the system but never puts significant pressure differential on the system. It won't "draw in moisture" through the cap and seals. By the same token, trying to move air through the system with positive pressure via the outlet of a fish tank pump is going to move air but not create a pressure differential. The system will be equally (in)vulnerable to water as with the OE vacuum system.

BTW, the reason the vented opti is important isn't because of moisture. It's because it helps prevent ozone buildup in the cap, which otherwise will cause corrosion and poor distributor performance. If your seals are good on the cap, water isn't getting in. If they are bad, water can get in regardless of venting or not.

cardo0

Ha, ha, ha. Vacuum moves air but doesn't never puts significant differential pressure on the system? More imagination engineering again. My car pulls nearly 18"Hg vacuum which is close to 9psi. The dynamic force of air moving at 100mph is only about 0.5psi. You are just full crap again. I wouldn't bother to even respond other than to warn others.

As usual I get 2 trolls on one thread. I think they're linked together - some type of bonding. :-

MatthewMiller

Yes, 18" of vacuum inside the manifold, which is caused by the pistons pulling intake suction against the throttle blade when it's nearly closed. There is pressure differential there, when there is minimal airflow. But open the throttle blade to WOT and what happens to all those inches of vacuum? That's right, the manifold vacuum goes to nearly 0", aka almost equal to ambient, because there is almost no restriction upstream of the manifold at that point (assuming the TB isn't massively undersized, the air filter and intake tubing are adequately sized, etc.).

It's the same story for the opti: it has a fresh-air opening that's the same size as the suction port. Ergo, there's nearly no restriction against which the vacuum port can exert any force (negative pressure, aka vacuum). So it moves air instead, which is the whole point of the vent system on the later optis. This isn't exactly rocket science here, cardo. But if you don't believe me, prove me wrong:

• Take an opti that's out of the car and rig up vacuum gauge. It won't be hard: just attach a T fitting to some vacuum tubing off the fresh-air intake side, and attach the gauge to the extra branch.
• Now put some tubing on the suction nipple and attach that to a vacuum source: a/c vacuum pump, fish tank pump, Mity Vac, whatever.
• Now with the non-gauge end of the T on the intake open, see how much vacuum you can actually pull.

To be sure, if you block the open intake end with your finger or a screw you'll be able to pull however much vacuum your suction source can muster and you will move no air. But with it open - you know, the way it is actually set up in the car - you'll pull no significant vacuum and you'll move lots of air instead.

cardo0

Ha, ha, I don't drive at WOT. At normal road speeds I have at least 12" of vacuum. And I know this because I have a manifold vacuum gauge mounted on my dash. And I recall it's tee'd into the same port the opti uses as my opti is a conversion from early non-vacuum vent to late vacuum vented opti as I run a late model opti and timing cover on my early model opti car.

So you want measure vacuum on the fresh air side side? How stupid! Of course it will near atmospheric or it should unless the intake duct has restriction. You don't even know how your intake works in front of and behind the throttle blades! Your ignorance is proven here. Yet I'm sure you will continue to run your mouth until it becomes another topic like formula engines.

Shut up and go away!

MatthewMiller

Yes, 12" in the manifold. How much vacuum is in your opti? You don't know, because you don't understand the system.

Guess what? The entire opti is the fresh air side, dumbass! There's no restriction anywhere in the airflow through the opti itself. You can put the gauge anywhere in the setup I described above. If it makes you happier, put the T on the suction side, with the vacuum pump on one leg, the opti on another, and the gauge on the third. That way the gauge can be between the pump and the opti, and you won't even need a hose on the fresh air intake nipple of the opti. You're still going to get negligible vacuum that way, unless you cover the fresh air intake with your finger. Like I said, this is easily proven, so prove me wrong.

Oh, you mean like in that thread where you got proven wrong and shut down by an acknowledged expert in the field? Yeah, I'd say this thread is headed in that direction.