1967 Big Block PVC valve

[Gary J.]

In the 1967 Judging Manual it mentions the 691C and 736 C PVC valve for the big blocks. In the 1966 Judging Manual it mentions the 691 C for the big blocks. So which would be correct for a September built 1967? 691 C or 736 C?

[Danny P.]

Re: 1967 Big Block PVC valve

In the 1967 Judging Manual it mentions the 691C and 736 C PVC valve for the big blocks. In the 1966 Judging Manual it mentions the 691 C for the big blocks. So which would be correct for a September built 1967? 691 C or 736 C?

For 67 691C or 736c can be used they were both used in 67 , hard to find13 Original PCV valve AC 691C.jpg

[Joe L.]

Re: 1967 Big Block PVC valve

In the 1967 Judging Manual it mentions the 691C and 736 C PVC valve for the big blocks. In the 1966 Judging Manual it mentions the 691 C for the big blocks. So which would be correct for a September built 1967? 691 C or 736 C?

Gary------


I would say almost certainly a CV-736C. I believe the CV-736C came into use in later 1966. Keep in mind, though, that there are at least several different configuration of the CV-736C. The earliest version had a cast top section.

[Gary J.]

Re: 1967 Big Block PVC valve

Gary------


I would say almost certainly a CV-736C. I believe the CV-736C came into use in later 1966. Keep in mind, though, that there are at least several different configuration of the CV-736C. The earliest version had a cast top section.

[Joe L.]

Re: 1967 Big Block PVC valve

Joe the 5th edition 1966 Judging Manual references the 691 C only. My ‘67 was built on September 20, 1966 so that why I was wondering about the 691 C. since it was built early in production.

Gary------

If the 1966 JG says that the 691C valve was used through-out 1966, then I think the JG is incorrect. I believe the 736C came into use sometime during the 1966 model year, probably about mid model year. Consequently, I don't see how any 1967 could have used that valve. If the 691C had been used throughout the 1966 model year, then I could see how an early 1967 could possibly have used that valve.

The 691C is one of these "treasure hunt" items. Once found and purchased for a king's ransom, 1966 L-72 owners want to believe their car came with it. I'll bet there are later 1966 L-72's out there that have 691C valves that never originally had one.

[Danny P.]

Re: 1967 Big Block PVC valve

1966 year they all used 691C then late 66 and into 67 691C and 736C were used, like Joe said the 736C came in different shapes, earliest version 736C came with a flat top look like the 691C earliest version and later years 736C came in Cap top shape , in your case Gary late 66 CV-736 were being used along with the earliest version CV-691C

[Joe L.]

Re: 1967 Big Block PVC valve

1966 year they all used 691C then late 66 and into 67 691C and 736C were used,

Danny-------


Not according to GM. GM states that the CV-691C, PRODUCTION part number 6421271, was replaced on 11/18/65 by the GM #736C, PRODUCTION part number 6423438. Of course, it could have taken several months for this to actually enter PRODUCTION but I would expect it would have occurred no later than mid model year.

[Danny P.]

Re: 1967 Big Block PVC valve

Danny-------


Not according to GM. GM states that the CV-691C, PRODUCTION part number 6421271, was replaced on 11/18/65 by the GM #736C, PRODUCTION part number 6423438. Of course, it could have taken several months for this to actually enter PRODUCTION but I would expect it would have occurred no later than mid model year.

That right Joe , CV-691C was the earliest version used back in 65 and 66 and eventually faded out in early mid 66 until it was replace by CV-736C earliest version of the flat top CV-736C into late 66 into 67.

[Gary J.]

Re: 1967 Big Block PVC valve

5E007910-CFDE-48EF-8D46-D13C61C6761E.jpeg B5C3F152-8505-4E17-807F-C6D91394CDF9.jpeg

[Tim G.]

Re: 1967 Big Block PVC valve

The 736C is hard to find, I've searched for one for two years for my '67.

[Danny P.]

Re: 1967 Big Block PVC valve

[ATTACH=CONFIG]101697[/ATTACH] [ATTACH=CONFIG]101698[/ATTACH]
The first picture is from the 1966 Judging manual, the second picture is from the 1967 Judging Manual. Looks like they both need to changed. It would be interesting to do a survey. Joe, do you have any pictures of the types used, of course I know they are “Not for Sale!”

Here the three PCV used 65 and thur 68 and on ,CV-691C used 1965 to mid 66, CV-736C flat top used mid 66 to 67, CV-736C with cap on top used in later years. Nos-Ac-Flat-Top-Cv691C-Pcv-Valve.jpgimages.jpgs-l300.jpg

[Ronald L.]

Re: 1967 Big Block PVC valve

If you look back about 8 - 10 years or so, you will find some part number research David L. and others, Decemebr 65 there was a change.

SHP got a new part number and that corresponded to the 736 valve. Very clear in the AIM, and service parts, in addition back then (2008-11 when all this was being discussed) I actually talked to the son who worked in that department with his father who was the manager at AC Spark Plug - of the PCV Valve department, about all of this including how to test these valves.

Another side note - At the 2011 National NCRS event there was a white haired gentleman that as we were discussing this topic walked by and said they (solid lifter higher reving SHP engines) were sucking oil...hence the new valve.

Yes they are hard to find in their correct configuration identical in appearance to the 691, appearance only - the inside was different!

Now to address the 691 - that stayed in production on the Low HP 390 400 HP versions until at least 1968. You can see the formed sheet metal versions of these valves for sale on-line with 1968 dates on the boxes and yep, probably have one or two.

The first (1966 and 1967) 736 valves were machined two piece housing construction.

They were followed by the solid top with stamped thin metal lower later in 1967, where later means 1967 calendar year.

Again more of these details are in the forum.

[Joe L.]

Re: 1967 Big Block PVC valve

The 736C is hard to find, I've searched for one for two years for my '67.

Tim------

The first design 736C is much more difficult to find than the early 691C.

[Joe L.]

Re: 1967 Big Block PVC valve

[ATTACH=CONFIG]101697[/ATTACH] [ATTACH=CONFIG]101698[/ATTACH]
The first picture is from the 1966 Judging manual, the second picture is from the 1967 Judging Manual. Looks like they both need to changed. It would be interesting to do a survey. Joe, do you have any pictures of the types used, of course I know they are “Not for Sale!”

Gary------


I have a few but they're so buried in Group 1 tote boxes that my back is telling me I'm not up to trying to "dig them out".

[Tim G.]

Re: 1967 Big Block PVC valve

Sometimes it's better to be lucky than smart, I found this in my "trinket" box with original radiator caps, oil caps and wing nuts. I had no idea I had one.