Cliff Harris

The parts book shows only one orifice tube for all years of C4s, 3033879, AC Delco 15-5151. I have heard that orifice tubes with smaller holes will work better at idle. Some research showed this:

Ford fixed orifice tubes:
Blue .067"
Red .062"
Orange .057"
Green .052"
Brown .047"

GM fixed orifice tubes:
White .072"
Black/White .072"

I also found this information on VOV (Variable Orifice Valves):

http://www.acsource.com/onsalesmartv...atormount.aspx

I have seen several recommendations to change to the Ford blue orifice tube to get better AC performance at idle. The VOV seems like the ideal fix. Does anybody have any experience with the VOV?

PcolaPaul

I use the Ford blue orifice tube for R12 to 134A conversions. Never used the variable type but have herd they can stick closed after time.

93VettePilot

I used a parts store stock replacement on my r134 conversion on my 93 Corvette about 4 years ago. Its still blowing cold and going strong. I would stay away from the VOV's for reliability purposes.