Re: CV 746 C PCV valve differences
 

I saw a survivior 1969 Z/28 at MCACN a few years ago with the heavier, spun steel PCV valve. Steve Shauger and Johnny K. might remember that car too. I also believe that the purple valves were 1970 and up over the counter. I personally never saw a purple PCV valve on an assembly line car but its tough remembering back that far for sure. I worked at a Sunoco and also a Hess gas station from around 67-68 to about 1971.I have seen survivor, one owner sb cars 307, 350 etc. with the heavier spun PCV valve but not sure if they were just in the early 69 model year or not. Also saw some 350 2 barrel 69 chevelles in the yards with the spun steel valves. Maybe John Karvonen and Dave Valentin can chime in here.

Re: CV 746 C PCV valve differences
 

https://www.yenko.net/ubbthreads/pics...65-photo_1.jpg

I've been using these - same style with no shoulder.

Re: CV 746 C PCV valve differences
 

The 691's are easier to find then the 746's it seem Bruce.
Cheaper too!

Re: CV 746 C PCV valve differences
 

Great topic and interesting thread. I believe like you Chris, that the flat top /spun type was 1969 production. Also I have seen the stamped raise on two late Oct 69 survivors but they may have been changed. The middle machined /raised is one I've not seen or am familiar with, but there may have been a transition period. I'll check some pictures I've take of cats built in that time period.

Re: CV 746 C PCV valve differences
 

use caution when buying ones that looks original. some on ebay have been questionable in my opinion. you can buy blue chem dye that machinists use to see lines scribed on metal. It can be had in a color very close to the factory purple dye.