But isn't your '68 exempt? Even in California smog tests are not required '75 and earlier. For cars earlier than that, and this would include your '68, any pollution control equipment original to the car needs to be maintained but no inspection pre '76 models. 1968 was a watershed year both for safety and emission control. I also have a '67 Jag XKE that I restored, I love it no polution control except a crankcase breather, no headrests, toggle switches on the dash, covered headlights. 1967 was a great year for cars, maybe the best imo.

It is now, but it wasn't in 1984.

Anyway - PM me if you decide to toss that DIverter valve. If I can open it up, install a fabricated diaphragm, and reseal it...it would be good to know.

I won't toss it and for sure I'll keep you in mind. Once I get it off the car I'll post some detailed photos, looking at it now I have no idea how it might come apart but maybe some clue will show up when it is off the air pump.

Ok so Dr. Rebuild doesn't have one and Bill Hodel has a good used one for $200. I just bought this NOS one on Ebay for about $175:

https://www.ebay.com/itm/1977-78-Cor...53.m2749.l2649

For now I'm going to pull the whole AIR system off the car and continue tuning, just realized that it is probably F-ing up my air/fuel readings.

Thanks again for all the help with the part numbers!

Good enough. I'd be willing to try and install a diaphragm and send it back to you. I'm only interested to see if it can be done with minimal tools. To see if the diaphragm housing can be opened up, or opened up with a dremel, fabricate a diaphragm, and then reseal with adhesives and/or some sort of clamping device????

Not to send this off on some weird direction, but I get ideas from post like this where he cut up a wiper door actuator.... pretty cool: https://www.corvetteforum.com/forums...-actuator.html

Attempting to fix it is something I might try but I probably wouldn't go to the lengths that you describe. Here are the photos, if you like a challenge then go for it. PM me your address and I'll send it to you. I shouldn't need it back, the NOS one arrives in a few of days but I'll wait until that happens before I send you this one just to be sure. One other thing, the guy at my local Corvette parts place said he thinks the diverters with the inline outputs were used on big block engines. You can probably trace the number, I tried but I could not get that wiki site to load.

PM sent.
Wiki page is working again today. It's where I got this image:

I received the NOS diverter valve today, it does not hold vacuum and from what I now understand, I don't think it's supposed to. Also, I might have found the cause of my high idle - premature centrifugal timing advance of my aftermarket MSD distributor. If true then my old diverter valve may not be bad after all. I still have a lot of work to do to sort all this out but at least I'm making progress although I may have just bought a $175 part that I don't need.

Well it's only money, right?

Not returnable? What is the test for diverter valves?

It's probably returnable, I'll decide whether to do that once I have everything sorted. Not sure I should inconvenience the Ebay seller for my mistake, and $175 is a fair price for one of these, especilly NOS so I can probaby sell it for what I paid. The test is on the car, with everything hooked up except an open AIR hose, rev the engine and then let it drop down. The resulting high vacuum should release a puff of air that you can feel through the open hose.

Keep in mind, the function of the diverter valve is to prevent backfiring in the exhaust on decelleration. Every time you back off on the gas, the diverter valve stops the air injection into the exhaust manifolds that would otherwise cause the popping backfire sound. If you can disable the diverter valve by plugging the signal hose (stop the vacuum leak) and do not have backfiring on decell, you don't really have a problem. You should
pass a sniffer test because the air injection is still pumping all the time.

So then I have it backwards in my last post which is entirely possible. That means air flow through the hoses would stop when the engine is slowing down and it would exit the vent holes in the housing. That might be a little harder to feel, maybe I can disconnect a hose at the diverter valve and peer into it looking for the piston to move.

The diverter cuts off the air to the exhaust manifolds on a spike in intake manifold vacuum such as snapping the throttle closed. You can pull the fat hose off the check valve at the end of the trees and feel the breeze at about 1500 RPM out of the pump then snap the throttle closed to see if the air stops while the intake vacuum is high. If the air flow stops while the vacuum is high, the diverter valve is functioning. The flow will come back during normal manifold vacuum.

If it seems to be working I would do a drive test to see if it backfires when you rev it up and quickly back off the gas. No "bang" means you can just go home and have a beer.

Jim__H
Ok, I actually got out my electric vacuum pump (Harbor Freight special - glad I have it for testing vacuum actuated systems and doing a/c evacuations) and tested my diverter valve.
At about 10-12" of vacuum (a/c gauge manifold not the most accurate monitoring system) the plunger actuates to divert flow, from going to exhaust manifolds, and redirects that flow to the muffler vent path.
I have an mp4 of it moving but I have to figure out how to load that. The internal assembly does NOT move very much, but you can see it move. While blowing throw the smog pump outlet you can feel the change (diversion), and since I had sprayed gumout within, I actually so the gumout come out of the muffler vents on the diverter valve when it moved..... anyway, a couple of pics....not much movement, but you can kinda/sorta see that it moved here....note that there is a slightly larger gap between the bottom of moving plug and the valve body (right side pic).
I'll go look around and see how to load and MP4 little video.....
Hope this helps someone.

That is some good work and very helpful, thanks.

You're right the piston inside sure does not move much. I don't know if I will get around to testing mine today, the used distributor that I tried yesterday did not work for me, I feel like I am chasing my tail on my high idle problem.

Does anyone know if it is possible to have a high idle (1100-1200) caused by a vacuum leak but with an air/fuel ratio slightly rich in the upper 13s? Assume that the carb is not the problem.