68 smog 427/435 C_3

[Michael Ketterer]

I checked the archives, two post on this but I need more info.
need the numbers that will work for elbow and adapter for diverter valve off the pump.
I have the pump correct for 68/69. Have the correct big block 68 brackets. I have the adapter for 69 427/435 they say, it has no numbers but is an offset two way that moves the elbow to a differant mounting position. I have a elbow Y1 3951346 but do not think its correct?
If some one could put me in the right direction, I would be most grateful
Thank you
Michael
Ps I do not own an AIM but wish I did, also I would like to make the smog system non working and any info on that would be great!

[Mark D.]

Re: 68 smog 427/435 C_3

Michael,

The best answer I can give you is to call Bill Hodel. Not only is he the most knowledgeable, he is also one of the nicest fellows you could possibly ever know. I know he would be more than happy to discuss your system with you.

His number is 330-832-0871.

Regards,

Mark

[Michael Ketterer]

Re: 68 smog 427/435 C_3

Mark
Thank you for the info!
I will call him.
Best Wishes for a Great Holiday!

[Joe L.]

Re: 68 smog 427/435 C_3

Michael------

The 1968 L36, L-68, and L-71 AIR system did not use either an adapter plate or an elbow between the pump and the valve. The valve bolted directly to the pump with only a gasket between them. For this to work, though, you do need the correct 1968 style pump (has relief valve on aluminum pump case) and the correct 1968 big block diverter valve. This valve is GM #7028296 and is stamped "28296". The pump is relatively easy to come by; the diverter valve is not.

The adapter plate, GM #3955222, was used for 1969 L-68/L-71 only and it was used with a different diverter valve than 1968. No diverter valve elbow was used for any 66-72 Corvette big block AIR system. An elbow was used for 1973-74 Corvette big block AIR systems and it's the 3951346 that you presently have.

Systems can be made dis-functional by removing the vanes from the pump, plugging the vacuum line from the carb to the diverter valve, and ensuring that the 2 check valves are in perfect working order. However, I absolutely DO NOT recommend doing this for a variety of reasons.

[Michael Ketterer]

Re: 68 smog 427/435 C_3

Joe Thanks
all the numbers!!!!
What knowlage,
Joe would you please tell me the diverter valve for the adapter 69 3955222
and are the 68 and 69 pumps not the same? With relief valve on top?
and I have a 29295 diverter valve, whats it to?
Thanks for a load of information already!
Hoping your Holiday Seasons the Best
Michael

[Joe L.]

Re: 68 smog 427/435 C_3

Michael-----

The diverter valve used with adapter 3955222 was GM #7029298, stamped "29298". This is a 1969 big block (except L-88/ZL-1) and 1971 LS-6 valve. The only application of the adapter plate for this valve, though, was 1969 with L-68 or L-71.

The 1968 and 1969 pumps are NOT the same EXCEPT that 1968 and 1969 L-88/ZL-1 are the same. The relief valve seen on the 1968 (and 1969 L-88/ZL-1) pumps is as shown in the below photo. The 1969 pump is exactly the same except without the relief valve (just an un-machined aluminum boss where the valve is for 1968).

The "29295" ID number is that used for the GM #7029295 valve. It was used for many 1969 manual trans equipped Chevelles, Chevy II, and Camaro with 302 and 350 cid small blocks. It is not configured properly for any 68-71 big block application, though.

[Michael Ketterer]

Re: 68 smog 427/435 C_3

Wow!
I just want to thank you for time and knowlage, Thank You very much.
I'm sure others are writing numbers down about this subject should they read it.
the pump the parts store tried to give me tonight was the 69 but my order ticket said 68 and when they pulled the picture up its just like yours.
And the mount point for the diverter is on the back of the pump, just like your picture.
so now how do you mount the diverter to the back of the pump to come out on top and parallel to the pump? as I have seen on L-71 (but never close up).See in Pictures.
Is the correct diverter valve elbowed itself? I never saw a pump with the diverter mount on the top side of a pump.
Thanks again Michael

[Joe L.]

Re: 68 smog 427/435 C_3

Michael------

The correct diverter valve does not have an integral elbow. I have some NOS examples of it around here [none for sale] but they're too hard for me to get at right now so I can't post a photo of one. If I get ambitious later, I might.

The 1968 (and 1969 L-88/ZL-1) pump with external relief valve can be used on ANY 1968-75 Corvette. However, the 1969 (except L-88/ZL-1) pump without external diverter valve CANNOT be used on any 1968 Corvette, UNLESS a 1969 or later diverter valve is also used. The 1968 diverter valves have no integral relief valve. All 1969 and later diverter valves (except 1969 L-88/ZL-1) do have an integral relief valve. So, if one uses a 1968 style pump on a 1969+ application with diverter valve with integral relief valve, you end up with two relief valves. Two relief valves is fine; NO relief valves is NOT fine.

The 1976-78 pumps which also have no integral relief valve can also be used for any 1969-75 Corvette (except 1969 L-88/ZL-1). However, their case configuration is slightly different and easily detectable by a knowledgeable individual. They're 100% functional, though.

[Michael Ketterer]

Re: 68 smog 427/435 C_3

Joe
You dont have to dig one out.
You have given me enough home work to do.
Thanks for all the numbers and info on the L-71 and other applications.
No wonder some of the diverter valves are hard to come by,
but mabey a later as you pointed out.
My only question still is
are the ports out of the top of the back plate of pump housing or are they out the back? for 68 L-71
Thanks so much
and really Best Wishes this Holiday season
Michael

[Joe L.]

Re: 68 smog 427/435 C_3

Michael-----

Well, I just happened to see one of the 7028296 valves when I went out to put another part away. You're lucky that my tote bins are "see through" type and I just happened to see the box. Anyway, here are some photos of the 7028296 valve.

Among other things, you will note that the muffler assembly is retained to the valve assembly using a spring clip. This is a feature unique to all 1968 valves as well as 1969 L-88/ZL-1. All other 1969 and later valves use a muffler that's crimped to the valve.

[Joe L.]

Additional Photo

Here's another view:

[Joe L.]

Another Photo

And, another:

[Joe L.]

And a Final Photo

The last photo:

[Michael Ketterer]

Re: 68 smog 427/435 C_3

I'm drooling.............................
ok how much?
My first born!
just kidding, I know ya said no sale.
and that one just bolts to the back of pump with the diverter kinda looking up at the sky from the pump?
Thanks for the picture I'm sure its the only one I'll see.
You have been very kind.
Thank you!

[Joe L.]

Re: 68 smog 427/435 C_3

Michael-----

I came across this NOS 1968 pump when I was putting the diverter valve away. Strange how one thing leads to another. This particular pump was actually manufactured in September, 1968. It's correct for all 1968 applications as well as 1969 L-88/ZL-1. You will note the configuration of the outlet. This is the same configuration as used for all 1968-78 pumps.

Pumps which have 2 or 3 ROUND outlets off of the backing plate of the pump are those used for 1966-67 passenger cars with K-19. Pumps with "plugged off" or unmachined bosses on the backing plate but with a "T" outlet coming off of the bottom of the pump's aluminum body are 66-67 Corvette with K-19 AIR pumps.