1966 JG question - PCV valve label for 427

[David L.]

Re: 1966 JG question - PCV valve label for 427

Not to be picky but the 6421981 is a CV691C not a CV691.
Hope this helps,Bob

Bob,

It doesn't help at all. I hate to be picky but both the "CV691" and "CV691C PCV" valves had the SAME PART NUMBER, GM # 6421981. I once owned a "CV691" PCV valve that I removed from a 1965 Chevrolet convertible w/original 396 engine back about 1979 or 1980 when I first started collecting parts for my 1966 Corvette. The "CV691" PCV valve was entirely constructed of "solid" steel (as opposed to "stamped" steel). My 1966 Chevrolet Parts Catalog (Oct. 1965) describes GM # 6421981 as "VALVE ASSY., vent (CV-691)". It is my belief that the "CV691" PCV valves were used on 1965 Chevrolets (396) and POSSIBLY "early" 1966 Chevrolets (396), 1966 Corvette(427). I sold the "CV691" back about 1990 or so for BIG $.

I also have owned several NOS "CV691C" PCV valves in boxes that that had date codes printed on the boxes, "8-67-5" and "1-68-6" (Aug. 1967 & Jan. 1968). The NOS "CV691C" PCV valves are partly "stamped" steel (large diameter end) and partly "solid" steel (small diameter end).

The "C" designates CONSTANT ACTION.

GM # 6421981 was replaced with GM # 6423695 (CV-736C) in July 1969 as per Chevrolet Parts History. The CV-736C PCV valves are entirely "stamped" steel.

Dave

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

Dave,

Are we expecting the 736 C valve for mid to late 66 cars?

[David L.]

Re: 1966 JG question - PCV valve label for 427

Dave,

Are we expecting the 736 C valve for mid to late 66 cars?

Ron,

I would think so.

The part number change from 6421271 to 6423438 (assembly manual part numbers, not service part numbers) theoretically changed on 11/19/65 but we all know that they used up the supply of parts on hand until these parts were gone. Who really knows when the physical change took place.

If the service part number 6421981 is the same for CV691 and CV691C I would think that 6421271 is the assembly manual part number for these 2 PCV valves.

My 1967 Camaro assembly manual shows 6423438 as the PCV valve part number for the 396 engine (L78).

Enclosed is a page from my 1967 Chevrolet parts catalog (page revised Dec. 1966), left photo.
Right photo is from 1967 Corvair-Chevy II-Chevelle-Camaro parts catalog (Oct. 1966). Note the 1st & 2nd design PCV valves used the 1966 El Camino (396).

Dave

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

David, 736C, as the detail you have shared shows, it has to be.

Thank you for the clarification.
Ron

[Bob J.]

Re: 1966 JG question - PCV valve label for 427

Bob,

It doesn't help at all. I hate to be picky but both the "CV691" and "CV691C PCV" valves had the SAME PART NUMBER, GM # 6421981. I once owned a "CV691" PCV valve that I removed from a 1965 Chevrolet convertible w/original 396 engine back about 1979 or 1980 when I first started collecting parts for my 1966 Corvette. The "CV691" PCV valve was entirely constructed of "solid" steel (as opposed to "stamped" steel). My 1966 Chevrolet Parts Catalog (Oct. 1965) describes GM # 6421981 as "VALVE ASSY., vent (CV-691)". It is my belief that the "CV691" PCV valves were used on 1965 Chevrolets (396) and POSSIBLY "early" 1966 Chevrolets (396), 1966 Corvette(427). I sold the "CV691" back about 1990 or so for BIG $.

I also have owned several NOS "CV691C" PCV valves in boxes that that had date codes printed on the boxes, "8-67-5" and "1-68-6" (Aug. 1967 & Jan. 1968). The NOS "CV691C" PCV valves are partly "stamped" steel (large diameter end) and partly "solid" steel (small diameter end).

The "C" designates CONSTANT ACTION.

GM # 6421981 was replaced with GM # 6423695 (CV-736C) in July 1969 as per Chevrolet Parts History. The CV-736C PCV valves are entirely "stamped" steel.

Dave

Your first post said its a 691 and I have a box thats a 691C.

[David L.]

Re: 1966 JG question - PCV valve label for 427

Your first post said its a 691 and I have a box thats a 691C.

Bob,

I don't really understand your comment.

The "CV691" PCV valves made in 1965 were actually stamped "CV691" on the PCV valve itself and were made from a "solid" piece of steel. I assume that if you bought one over the counter in 1965 the box would have CV691 on it as well as the GM part number 6421981.

If you bought a 6421981 in August 1967 (or even earler) it would come in a box labeled "CV691C" along with the same GM part number 6421981. I once owned several of them with 1967 and 1968 date codes on the boxes. This PCV valve was stamped "CV691C" and was made of "stamped" steel as well as "solid" steel.

I do not know when the actual change was made from the "CV691" PCV valve to the "CV691C" PCV valve but my guess is the Fall of 1965 or the Spring of 1966 but who really knows.

Dave

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

David,

I just found this today - does this meet the criteria for the mid to late 66 & 67 427 PCV valve for the 390HP?

See picture...


and then - to confirm the thread, the 736C label is Orange with white lettering, correct?

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

Note the prior picture has Delco Rochester.

This part appears to be a " NEW" current Delco version...

notice logo is different.

[David L.]

Re: 1966 JG question - PCV valve label for 427

David,

I just found this today - does this meet the criteria for the mid to late 66 & 67 427 PCV valve for the 390HP?

See picture...


and then - to confirm the thread, the 736C label is Orange with white lettering, correct?

Ron,

I really do not know. Aren't the CV736C PCV valves all the same? Is there a date code on the box? I never really studied these PCV valves because they are so common. I have an orginal CV-736C valve from a 1970 Chevrolet that I am saving for my 1970 Camaro SS350 project.

I have 2 NOS CV736C PCV valves. One box is dated "71" and one is dated "6 84". They are not exactly the same but very close.

I also have 6 used CV736C valves from various 1969, 1970, 1971, and 1972 Chevrolet models. I will have to clean them so I can compare them, maybe tomorrow evening. I do not have any of these valves from cars earlier than 1969.

I do have one used CV736C valve (source unknown) that is slightly longer, about 1.69" long. The other 8 CV736C valves that I have measure about 1.62" to 1.65" long.

Dave

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

David,

The NOS piece has a box date in the late 80's or early 90's - I assume that is the two digit number in the flap area. This piece has the ticks of upset metal that would seem to serve as retention aids. I can get measurements on this tomorrow.

The new piece has the new Delco logo, FWIW this measures 1 5/8"

[David L.]

Re: 1966 JG question - PCV valve label for 427

Rod,
In my collection of 8 CV736C PCV valves I have basically 3 diifferent versions.

1. The used CV736C valves that I obtained from 1969-1971 Chevrolets and my NOS CV736C valve in a box dated "71" are very similar. The lengths vary from 1.61" to 1.63" (1 5/8"). The "AC SPARKPLUG" AND THE "TYPE CV-736C" stampings have a space between them that measures about 0.07". There are 4 "punch marks" around the bottom perimeter equally spaced.
The 1970-1971 valves have a "D" on the bottom end. The 1969 (from Nov. 1968 engine) valve does NOT have any letter on the bottom end.

2. The used CV736C valve (O.L. = 1.61" with "D" on bottom end) that I obtained from a 1972 Chevelle Malibu S.W. and my NOS CV736C valve (O.L. = 1.64" with "M" on bottom end) in a box dated 1984 are very similar. There are 9 "punch marks" around the bottom perimeter equally spaced). The spacing between the 2 stamped lines it further apart and measures about 0.20"

3. The 3rd different CV736C valve that I have which I found in a 1970's (or maybe 1960's) GM vehicle (but not a Chevrolet) is much longer (O.L. = 1.68" or 1 11/16"). There are 4 "punch marks" around the bottom perimeter equally spaced. The spacing between the 2 stamped lines measures about 0.07" just like my 1969-1971 versions. There are ALSO 2 vertical line segments stamped on each side of the stamped lettering. This valve does NOT have a letter on the bottom end. I suspect this version might be an EARLIER VERSION than the 1969 valve since it is noticable longer (about 0.05" to 0.06" or 1/16") and there is no letter on the bottom end. Maybe this is the 1966-1967 version even though I found it on a 1970's (or maybe it was 1960's) GM (but not Chevrolet) vehicle. This valve is the one in the upper left in both pictures. I think it makes sense that the length of the CV736C was shorter in later years. Also note that the "collar" (0.87" dia.) is at the top of the 0.73" dia. section on this valve where this collar is located about 0.25" lower than the top section of the 0.73" dia. section on the other valves.

By the "bottom end" I mean the movable part inside the valve.

Enclosed are pictures.

Dave

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

David,
I know these had a letter underneath and I can get that. They also have the 9 dimples or dots.

What is interesting here is that the ones I saw had AC Rochester.

In the GM history of AC Delco Rochester, etc. What combination let to AC Rochester versus AC Delco? Could these be earlier? I think a few months ago I posted the history here - now I have to find that.

[Ronald L.]

Re: 1966 JG question - PCV valve label for 427

From this article it would seem the AC Rochester version of this valve was 1988 - 1994...

Rochester Products Division was a division of General Motors that manufactured carburetors, and related components including emissions control devices and cruise control systems in Rochester, New York. It began as North East Electric Company in the 1800s. The 2G (later 2GC and 2GV), commonly called DualJet, was introduced in 1955, and continued to be used on GM V8s until at least 1969.[1] In all, it was used in at least 125 applications, including the Brockway's inline six.[2]
The company is best known for their highly regarded Quadrajet carburetor, which was originally designed in the 1960s and continued to meet emissions standards into the 1980s. The Quadrajet became computer controlled in 1980 in California and in 1981 in the rest of the states; its last application was on the 1990 Cadillac Brougham and 1990 full size GM station wagons with the Olds 307 engine. Its longevity is a testament to the expert engineering achieved at Rochester Products Division and GM, even to this day, as RPD was a pioneer in fuel injection systems in road cars in the 1980s when they became the standard fuel induction system. In addition to carburetors, Rochester also made various emissions control equipment such as charcoal canisters, which found use in GM vehicles as well as those from other makes. The last major carburetor design by Rochester was the Varajet II, essentially a Quadrajet halved lengthwise, and was one of the few successful 2-barrel carb with a "secondary". It was installed on 4- and 6- cylinder engines from 1979 to 1986 when all GM V6s went to Electronic Fuel Injection. Rochester is now part of Delphi and continues to manufacture fuel injection systems in Rochester, NY.
In 1981, Rochester Products and Diesel Equipment Division merged. The headquarters remained in Rochester. DED had plants in Grand Rapids, Michigan. [3]
In 1988, Rochester Products and AC Spark Plug merged. [4] The diesel fuel injection business was sold to Penske.
In 1994, the Grand Rapids operations of AC Rochester were spun off.[5] (132nd Page of 162)

[David L.]

Re: 1966 JG question - PCV valve label for 427

David,
I know these had a letter underneath and I can get that. They also have the 9 dimples or dots.

What is interesting here is that the ones I saw had AC Rochester.

In the GM history of AC Delco Rochester, etc. What combination let to AC Rochester versus AC Delco? Could these be earlier? I think a few months ago I posted the history here - now I have to find that.

Ron,

Based on my very recent research (just this evening) this is what I think about CV736C PCV valves at this point in time (obviously subject to change):

1. 1969 and older CV736C PCV valves do not have a letter on the bottom.

2. 1970 to ???? (and before 1984) CV736C valves have the letter "D".

3. 1984+/- CV736C valves have the letter "M".

4. 1971 and older CV736C valves have 4 "dimples" (or "punch marks").

5. 1972 and newer CV736C valves have 9 "dimples".

6. 1966-1967+/- (and maybe 1968) CV736C valves MIGHT be slightly longer (1.68" or 1 11/16") with the "collar" located at the top of the large diameter section making the length of the large diameter section 1.00" long. This length measures about 0.75" on 1969 and newer CV736C valves.

7. It would be nice it other Corvette owners that have their original CV736C PCV valves would join in a survey.

8. If there is no interest on this subject I will put the 1.68" long CV736C PCV valve mentioned in comment #6 above on Ebay to see what the rest of the world thinks.

Dave

[David L.]

Re: 1966 JG question - PCV valve label for 427

Update:

I have found some additional information about the 1967 Corvette 427 PCV valves in one of my notebooks. In 1993 I sold a NOS CV-691C PCV valve to someone on the east coast that owned a "very very original 67 435 HP 6500 mile coupe". After he received the NOS valve he wrote me back commenting about the CV-736C PCV valve that was in his 67 Corvette 427 stating the following:
"it appears to be solid steel - the length is the same as the NOS 691C you sent me. However - The bottom of mine is not flat but exhibits a slight chamfer. In addition the letters + numbers are as follows: AC SPARK PLUG TYPE CV-736C one line encompassing the circumference."
He also wrote the following:
"There is no doubt that the 1967 435 HP (Sp Hi Per) motor came with the 736C - Your thoughts?".

After studying these CV-736C PCV valve for the last few days it now appears to me that CV-736C version of the PCV valve used on the 66-67 Corvettes w/427 was "solid" steel, 1.68" in length, slightly chamferred bottom section (45 degree beveled bottom edge), and with the "AC SPARK PLUG TYPE CV-736C" stamping all in a single line (not 2 lines like the CV-736C valve made in 1969 and later years).

According to my 1967 Corvair-Chevy II-Chevelle-Camaro parts catalog (effective Oct. 1966) the CV-736C valve was also used on the 66 CHEVELLE (S.S.)w/Sp. H/Per., H/Per.)(396) and the 66 EL CAMINO w/(Sp.H/Per.)(396)(2nd Design). I would assume these models used the same version CV-736C valve as the 66-67 Corvettes(427).

Is there anyone out there in Corvetteland, Chevelleland, or El Caminoland that has one of these "solid" steel CV-736C PCV valves in their 66 or 67 Corvette 427? I have never seen this version of the CV-736C PCV valve. I just know of one from a very reliable source.