PCV valve or fixed orifice? - Moparts Forums

Register Log In Moparts Forums Moparts Question and Answer PCV valve or fixed orifice?

Print Thread

PCV valve or fixed orifice? #2760163 04/04/20 09:04 PM 04/04/20 09:04 PM
Joined: Apr 2006 Posts: 4,220 West Plains, MO DrCharles OP master
DrCharles OP master Joined: Apr 2006 Posts: 4,220 West Plains, MO	I've been having an interesting time trying to tune my idle and light throttle AFR (Holley 4780-2 DP converted to adjustable orifices and 4-corner idle). Due to the 451's big cam (272@.050) the idle vacuum is 8" at 1200 rpm, and about 14" at a 3000 rpm cruise. It likes around 13:1 on the wideband at idle. I still need bypass air (four 1/16" holes in the air cleaner stud) to have the correct throttle butterfly position. I had not given much thought to the PCV system, other than to find a valve that would fit my valve cover grommet and hook it up (through a small oil separator) to the big port on the back of the carb. So now I'm wondering if I should have a specific part number of PCV valve since my idle vacuum is significantly less than my cruise vacuum? Or use a fixed orifice that gives me the right idle rpm? Any thoughts? thanks.

Re: PCV valve or fixed orifice? [Re: DrCharles] #2760169 04/04/20 09:18 PM 04/04/20 09:18 PM
Joined: Jan 2003 Posts: 30,989 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,989 Oregon	I'd experiment with a fixed orifice size and see how it goes. Start out small, maybe 1/16th and see how that works. I wouldn't think you would need much more than that, maybe 3/32 at the largest.

Re: PCV valve or fixed orifice? [Re: DrCharles] #2760324 04/05/20 11:09 AM 04/05/20 11:09 AM
Joined: Jan 2003 Posts: 1,908 Nebraska 4 4406bbl top fuel
4406bbl top fuel 4 Joined: Jan 2003 Posts: 1,908 Nebraska	Originally Posted by DrCharles I've been having an interesting time trying to tune my idle and light throttle AFR (Holley 4780-2 DP converted to adjustable orifices and 4-corner idle). Due to the 451's big cam (272@.050) the idle vacuum is 8" at 1200 rpm, and about 14" at a 3000 rpm cruise. It likes around 13:1 on the wideband at idle. I still need bypass air (four 1/16" holes in the air cleaner stud) to have the correct throttle butterfly position. I had not given much thought to the PCV system, other than to find a valve that would fit my valve cover grommet and hook it up (through a small oil separator) to the big port on the back of the carb. So now I'm wondering if I should have a specific part number of PCV valve since my idle vacuum is significantly less than my cruise vacuum? Or use a fixed orifice that gives me the right idle rpm? Any thoughts? thanks. Check out Wagner dual flow adjustable pcv valve. There was a group buy here a while back.

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1