First Generation Firebird-L Mailing List ......................................................................... Danny,
On a Quadrajet, the lower port on the front driver's side the hookup for "ported vacuum", and it commonly goes straight to the distributor only. This ported vacuum lies above the throttle blades, therefore, at idle, this port has no vacuum, since the throttle blades are closed; and hence it does NOT pull your vacuum advance ahead. But, when you press on the accelerator, the blades open up, vacuum is then present at this port, and then your distributor kicks in the vacuum advance. The port on the back of the carb at the base is "manifold vacuum". This is always on. This gets hooked up to your brake booster, or any other device in the car that always needs vacuum. The hard line to your trans should be for your TH-400 tranny vacuum modulator. The other port at the back should go to your secondaries choke pull-off. Read this thread for more info: http://www.chevytalk.org/fusionbb/showtopic.php?tid/214605/ Not to say we can't help you, but there is a WEALTH of information at your fingertips on the Internet. Utilize Google or any search engine to look for info, which is how I found the article above. Search "quadrajet ported vs manifold vacuum." Remember, lots of these GM cars have similar parts, so you don't necessarily need a Firebird manual. Ciao, Thomas -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of D Dutch Sent: Tuesday, September 01, 2009 11:10 PM To: [email protected] Subject: [FGF] Vacuum Madness First Generation Firebird-L Mailing List ......................................................................... Alright, here's my first conundrum. - Anyone have any idea why (and I'm no expert at all, learning about vacuum as I go) someone would connect a vacuum line from the vacuum port on the front of the carb (original 1968 Rochester 4-bbl) straight to the advance port on the distributor? - looking from the hood the carb port I am referring to is on the lower driver side front of the carb. The rest of my current vacuum mess is as follows: - All the TVS ports are capped (I know 4 and 5 should be from service bulletin 68-T-2) - Port on front of carb (upper passenger side) has hard line going down to trans. - Port on side of carb (passenger side) is capped (OK per service bulletin 68-T-2) - I had a problem where all four barrels weren't opening and discovered that there was an open vacuum port on the back of the carb that was open - it is now capped and all 4 barrells open but I don't know where it should go. Any and all help is greatly appreciated as i try to sort this out. I've been reading here (http://firstgenfirebird.org/FAQ/engine/carburetor.html) but am still unsure where the port on the back of the carb should be connected and why someone made the connection they did to the distributor adcance port. -Danny -- 1968 Firebird 400 Conv. ------------------------------------------------------------------------ Submissions to Firebird-L: <[email protected]> Unsubscribe from Firebird-L: <[email protected]> Help: <http://FirstGenFirebird.org/firebird/Firebird-L.html> Classifieds: <http://FirstGenFirebird.org/ubb/> Owner Pictures: <http://FirstGenFirebird.org/show/> ------------------------------------------------------------------------ Submissions to Firebird-L: <[email protected]> Unsubscribe from Firebird-L: <[email protected]> Help: <http://FirstGenFirebird.org/firebird/Firebird-L.html> Classifieds: <http://FirstGenFirebird.org/ubb/> Owner Pictures: <http://FirstGenFirebird.org/show/>
