Exhaust popping fix explained

[Gary S.]

First of all, thank you all who posted. My moderate+ exhaust popping during deceleration, going downhill, and shifting was indeed the AIR diverter valve failure. I talked with Bill Hodel and the fix is:
1. replace at $500 (not in the cards right now)
2. replace with similar or look alike at $300
3. Neuter the air pump $100. This is John Hinckley's solution and is fully reversible. Remove the vanes of the air pump, block the signal hose to the pump and block the exhaust gases at the AIR manifold tree.

I chose door #3 and, although not as easy as welding the tube closed at the exhaust manifold as was suggested in my first post. In addition, I checked my carb and it was properly adjusted. The car runs amazingly well. At cruise, the car never ran poorly but at partial throttle and low speed acceleration it wasn't a pretty ride. Now it is just as one would expect with a beautiful sound, peppy acceleration and great low speed, partial throttle acceleration.

Thank you all.

Gary

[Mark E.]

Re: Exhaust popping fix explained

I like your route of "neutering" the pump rather than closing the tubes in the manifold. Doesn't neutering eliminate most of the parasitic power loss, while closing the tubes might actually increase pump pressure, and hence, power loss?

Your results explain why so many of these systems were simply removed back in the day. Not to mention a cleaner looking engine bay...

Does a diverter valve really cost $300 - 500?

[Gary S.]

Re: Exhaust popping fix explained

Actually, I got the term and the idea from John Hinckley and I recall that he said that there is no longer anything in the pump to create drag and it is essentially a pulley. I will be sending my pump out in a week or two.

Diverter valve at $500? Yes, for a correct part. I was quoted that for an exchange or a rebuild of mine. For a couple of hours of work both from the top of the engine bay and underneath it, I think this was the way to go, imo. Of course, as I get older my aches and pains become major after this kind of work. In the end, it was worth it because the car runs so much better.

Gary

[Edward B.]

Re: Exhaust popping fix explained

Gary, you can do the job yourself. It's dirt simple. All you need are some standard tools. I did this on my L36 a year or so ago.

Here are a few sites that show you how:

http://broachbuster.com/id50.htm

http://www.superchevy.com/how-to/additional-tech/1504-how-to-de-vein-or-rebuild-your-gm-smog-pump/

Ed

[Gary S.]

Re: Exhaust popping fix explained

Interesting Ed. But a hammer and chisel to break the vanes apart? Did you really do that or did you try and remove them intact? It looks easy except for the hammer/chisel part.

[Edward B.]

Re: Exhaust popping fix explained

Nope. just chisel them out. It was very easy and here's the result.

(NOTE: The picture attached is NOT my original 1969 L36 AIR pump, but one I happened to have laying around in my garage.)

However, if you have a rare pump, or numbers matching and don't feel comfortable doing this yourself, by all means send it out. Or, get a cheap one on ebay to practice with!

Ed

[Mark E.]

Re: Exhaust popping fix explained

If neutering involves a hammer and chisel, is it really "fully reversible"? (For some reason, I winced while typing that.)

If not, maybe save your original AIR pump for shows and neuter another for the street.

[Gary S.]

Re: Exhaust popping fix explained

"Fully reversible" is Bill Hodels description. Hammer and chisel seems most definitely non-reversible unless there is a rebuild in store.

[Edward B.]

Re: Exhaust popping fix explained

I have no idea what Bill's procedure is, but my way is definitely NOT reversible!

(Unless I can get my wayback machine working)

Ed

[Gary S.]

Re: Exhaust popping fix explained

Pretty soon those of us who know about the "way back machine" will have to start splainin to the others

[Edward B.]

Re: Exhaust popping fix explained

I guess it's actually WABAC MACHINE!

Ed

[Gary S.]

Re: Exhaust popping fix explained

Exactly. Now I don't know your age but I watched this. Can I use it to back to 1963 and order up a Corvette?

I am a stickler for searching on the various websites (and I DID search and read here) I visit before I pose a question. The thing I learned here was that there are very few surprises and even fewer new malfunctions on these old cars. I posed my original question with the clear understanding that this was carb or ignition related, not emissions. Of course, I was wrong. I had read numerous exhaust popping questions and many of you suggested the diverter valve to the poster, a few suggested timing, valves, rich/lean carb settings, etc. Because of the strong fuel smell when parked in the garage, I felt certain it wasn't the diverter valve. After fixing my problem, I went back and re-read the searches I had done and the solution was as plain as day.

Thanks to all and now all I have to do is go back under the car and install some ignition shielding and the drive this car.