Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: richnlean on July 10, 2014, 05:05:23 PM

Title: Confused about PCV port diameter
Post by: richnlean on July 10, 2014, 05:05:23 PM

Hi all,

I recently obtained this Qjet from a friend (# 7045268  T4  0515) for my 1975 Pontiac 400 (557 casting) block. I've checked the PCV valve, and for several years, they all seem to take the standard 3/8" fuel line, which makes sense. My 78 Firebird has the normal 3/8" PCV line as well. Heck, even Chevrolet used the same PCV diameter for a few decades so I'm puzzled. The diameter appears to be about two sizes up from the choke pull-off vacuum line diameter, give or take. So my question is, did someone switch out the throttle plate with some weird random one that did not originally belong to this carburetor?

I've circled the area in green found below:

(http://i151.photobucket.com/albums/s125/poopubucket/qjet_pcv_zps4343dd58.jpg)

Title: Re: Confused about PCV port diameter
Post by: qjetsrule on July 14, 2014, 10:14:55 PM

the pontiac pcv may still be 3/8" but the fitting is usually in the valley tray underneath the intake manifold. i'm not sure if this is the correct location for a 75, but the earlier models used the valley tray. good luck

Title: Re: Confused about PCV port diameter
Post by: qjetsrule on July 15, 2014, 05:14:43 PM

sorry, my info was incomplete. the pcv valve is in the valley tray and connects to a 3/8" fitting threaded into the intake just fwd of the carb. as i said before this is what i observed on earlier models and pontiac could have changed it by 1975.