C = Commercial?

[G B.]

Thanks to everyone who responded to my post below about 1963-4 PCV valve use (#590 vs. #590C). It appears that no one can identify the exact introduction date or specific assembly line application for the machined 590C version. Duke, I do understand that your 340hp '63 was originally equipped with a silver 590C.

In my late 1966 P&A Catalog, there are many ventilator valve (PCV) assemblies listed in Group 1.745. The only listing for '63-4 Corvettes is the 590. The 590C is not listed for any application. However, there are several other "C" suffix valves shown for trucks and taxis. Is it possible that the C stands for "commercial" use?

[Duke W.]

Re: C = Commercial?

Maybe my mind is playing tricks on me again. I recall that my original
valve was bright metal, but I can't swear that is was a 590 or 590C.

As I said in my previous post, all but a handful of of the part
numbers in my Delco catalog PCV valve number master list have a "C" suffix, and the handful that did not were something other than conventional PCV valves. The index page has a list of abbreviations and a "CV" prefix means "PCV valve" while a "C" suffix means "air filter element". Go figure! I guess if you take broad view a PCV valve has something to do with filtering air.

My '63 ownwer's manual does not have a part number for the valve, but does have
photos, and the valve in the photo looks to be threaded together, not crimped
I suspect the photos are of prototype parts.

Duke

[Robert Jorjorian]

Re: C = Commercial?

Jerry, I do not think Chevrolet P&A catalogs ever listed a 63-64 Corvette crankcase valve as a 590C.From 1962 through 1980 every Chevy parts book I have only lists it as 590 even though when the number changed to a 6421934 the part was stamped with a "C".

Part number 5649689 was the only GM part number listed in every Chevy P&A parts book for the 1963 Corvette aplication during ALL of 1962 and 1963(including the following dated P&A books 10/62,3/63,5/63,7/63).As I stated in the earlier post a NOS 5649689 in a 5/63 AC box does not have a letter "C" after the 590 on the box or the part.That same number was the only valve listed even in my July 64 P&A parts book.

If you want an exact date for change by running the 5649689 number thru a parts history book the 5649689 valve is replaced by a 6421934 valve on 1/66. That 6421934 number is the 590C valve that was available until recently. Everyone I ordered thru Chevy came through zinc or cad plated with a 590C stamped on the side.Without exception everyone I ran across on old dealership shelves were also stamped 590C. None were ever the short machined style like the earlier part number listed through 63.Though parts the 590C showed up AFTER 1965.

Regarding the letter "C".... RUMOR has it that during 1965 the 590 valves were changed in design to be self cleaning.....possibly the C pertains to that.

Yesterday I incorrectly stated by memory what the circular tag inside a NOS 590 box dated 5/63 read.Today I looked and the tag reads "AC" on top and "CV-590" on the bottom side.

[G B.]

Ah... I finally get it.

I appreciate all your research, Bob.

Then a 590C valve must be a replacement when found on a '63-4 Corvette, regardless of it's appearance (machined or crimped, silver or black, etc.).

[Robert Jorjorian]

Re: Ah... I finally get it.

Yes Jerry that is correct!

[Mike McKown]

A little late for this but,

I looked in my '63 dated TRUCK parts book. There are NO PCV's listed with a "C" suffix.