What PCV Valve is this?

[David S.]

Hi Guys,

I have this original PCV Valve. Can someone tell me what it belong to.

AC SPARK PLUG
TYPE CV 736C

Thanks,
Dave

[Tom B.]

Re: What PCV Valve is this?

When I worked in Chevrolet parts back in the '70s it seems that nearly every Chevy V8 used a 736. It was the most common with usage over several years. Probably other GM lines used it too.

Tom

[Joe L.]

Re: What PCV Valve is this?

Hi Guys,

I have this original PCV Valve. Can someone tell me what it belong to.

AC SPARK PLUG
TYPE CV 736C

Thanks,
Dave

Dave------


There are so many applications for this PCV valve it would be impractical for me to list them. As far as Corvettes go, it was used for virtually all 1967-73 except L-88, LT-1, and L-82.

[David L.]

Re: What PCV Valve is this?

I have 8 CV736C PCV valves (3 NOS in boxes dated 1971, 1972, and 1984) and 5 used (1969, 1971, and ????).
Seven of them measure 1.62" long and one measures 1.68" long. Most have 4 "punch marks" (1969-1972) and one has 9 "punch marks" (1984). I believe the oldest one is the one that measures 1.68" long (1967 vintage?).

Dave

[David L.]

Re: What PCV Valve is this?

Pictured are 3 different CV736 PCV valves:

Left:
"early" version, O.L.= 1.68"
stamped "AC SPARK PLUG", "TYPE CV 736C"
4 punch marks


Center:
Orig. 1969 Chevrolet, O.L. = 1.62"
stamped "AC SPARK PLUG", "TYPE CV-736C"
4 punch marks
"D" on bottom
The NOS valves in 1971 & 1972 boxes are the same.
The original valve from 1971 Chevelle is the same.

Right:
NOS in 1984 box, O.L. = 1.62"
stamped "AC SPARK PLUG", " TYPE CV 736 C"
9 punch marks
"M" on bottom

Basically I have 3 different styles of the CV736C valve.
The "early" version is totally different.

Dave

[Ronald L.]

Re: What PCV Valve is this?

The earliest version is completely different from any of the pictures posted

[Paul L.]

Re: What PCV Valve is this?

Along the same lines, what is the application(s) for CV 774 C?

[David L.]

Re: What PCV Valve is this?

Ron,

As I stated the "early" version is totally different. Even though the total length is only 0.06" longer (1.68"-1.62") the bottom section (3/4" dia. section) is about 1.00" long while the others are about 0.78" or 0.79" long. I believe that the "early" version was used in 1967 and possibly even 1968.

Dave

[David L.]

Re: What PCV Valve is this?

Along the same lines, what is the application(s) for CV 774 C?

CV774C is not listed in my 1970 AC Wholesaler's and Dealer's Catalog for Positive Crankcase Ventilation. The highest number listed is CV756C. I really do not have the time to check through my other 55 different vintage Chevrolet parts catalogs.

[Joe L.]

Re: What PCV Valve is this?

Along the same lines, what is the application(s) for CV 774 C?

Paul------


As far as Corvettes go, the CV 774C is applicable to all 1974-81 Corvettes except L-82. There are MANY other non-Corvette applications of the valve over about that same period.

[Paul L.]

Re: What PCV Valve is this?

Paul------


As far as Corvettes go, the CV 774C is applicable to all 1974-81 Corvettes except L-82. There are MANY other non-Corvette applications of the valve over about that same period.

Thank you, Joe. My 1974 is an L-48 so it looks like all is well!

[Joe L.]

Re: What PCV Valve is this?

Thank you, Joe. My 1974 is an L-48 so it looks like all is well!

Paul-----


Functionally, any CV 774C will work for you. However, like most other PCV valves, the configuration likely changed slightly over the years. So, one you buy today likely won't appear exactly like one purchased in 1974.

[Timothy B.]

Re: What PCV Valve is this?

Does anyone have an opinion on what the #'s, (726-774 etc) on the PCV valve mean. Are they some sort of flow number?

[Ronald L.]

Re: What PCV Valve is this?

Tim,
Those are AC SP model numbers and refer to the design level, not sure one could say flow completely since the design varies take the 726 for 327 and 736 for SP Hi PERF 427 for example.

One could measure flow to know the difference in spring tension though. Its my estimation that this will be the difference we see in the 691 and 736 valves.

Dave,
In you picture you show 3 valves - all stamped construction. I am referring to the machined solid steel version of our threads from last year.

IMHO - the 736 was introduce mid model year 1966 for the 427 - 425 HP, check the prior threads and the 66 AIM. SP HI PERF meant just that in 1966 SHP=425HP, not the 390 HP engine.

[David L.]

Re: What PCV Valve is this?

Dave,
In you picture you show 3 valves - all stamped construction. I am referring to the machined solid steel version of our threads from last year.

IMHO - the 736 was introduce mid model year 1966 for the 427 - 425 HP, check the prior threads and the 66 AIM. SP HI PERF meant just that in 1966 SHP=425HP, not the 390 HP engine.

Ron,

I believe that you are correct about the CV736C PCV valve starting sometime during the 1966 production but I do not have any documentation to prove that. The 1966 AIM shows GM # 6423438 as the PCV valve (replaced by the 6421271 on 11-19-65 as per the revision record) for the L72 engine (427 SHP).

I firmly believe that GM # 6421271 = AC # CV691 (or CV691C).

According to my 1970 AC PCV valve catalog CV691 or CV691C is not listed because it was discontinued.
However, GM # 6421272 = CV692C. Wouldn't it be logical that GM # 6421271 = CV691C (or CV691)?

Also in this 1970 AC PCV valve catalog GM # 6423428 and GM # 6424251 are not listed because they were discontinued. I believe the following MIGHT be true:
CV736C "1st version" = GM # 6423438 (1966 & 1967 AIM)
CV736C "2nd version" = GM # 6424251 (1968 & 1969 AIM)
CV736C "3rd version" = GM # 6484541 (as shown in 1970 PCV valve catalog)

NOTE: The GM parts numbers in the Chevrolet parts catalogs are TOTALLY DIFFERENT than the AIM part numbers.

I don't really remember but was the "1st version" CV736C PCV valve the solid steel type?

BTW, I just started a thread about AC PCV valve conversion numbers late last night based on my 1970 AC PCV valve catalog.

Dave