Come on out there,Firebird folks...someone has to have a 67 326 HO car that could help me out,right? Any input would be appreciated! Hello out there-I have a 67 326/2bbl car that I'm installing a factory 4bbl.intake&Carter AFB combo that was supposedly from a '67 326 H.O. motor. There is no part number I can find on the AFB...Is there a difference between a manual trans carb and an automatic carb? My car is a 4 speed car. I'm guessing that an auto trans carb would have a vaccuum secondary and a 4 spd. carb would be mechanical? Also, on the front of the intake where it meets the water pump, there is a threaded area where it looks like a bolt should go to help seal this area. The old intake did not have a bolt there,but there was a decent amount of gasket maker smeared around it which perhaps kept it from leaking? The water pump housing is also "notched" at this area-again,indicating that a bolt perhaps goes from water pump housing to intake? Any insight would be great! Thanks-Jeremy jck7512@ptd.net

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Jeremy
'67 326/4spd ragtop

well i would be of no help on the carb question, but i can help with the intake one

yes there is a bolt the goes from the water pump housing to the front of the manifold under the thermostat
you should put all the bolts in loosely, then tighten this front bolt to get a good seal there, then tighten all the other manifold bolts

Sorry for the delay. Check the AMA section of this site for P/N on the Carter AFB for 326 HO.

http://firstgenfirebird.org/firebird/1967/ama/10.pdf

Here's pictures of the Carter on my automatic-equipped original 326 HO. It has vacuum secondaries - I'd be surprised if the manual had mechanical. I can send hi-res directly if you wish.

Very few Carter AFB carburetors have a vacuum secondary. Some of the very first AFB's (1957, and 1958) used by Ford and Chrysler were vacuum secondary units.

Very few Carter AFB carburetors are true "mechanical secondary" carburetors. Without going through the 505 different AFB's, I remember a couple of Chrysler applications, and a couple of marine applications.

Like the later Q-Jets and TQ's, most Carter AFB's are a mechanical secondary WITH an auxiliary airvalve. Some refer to these as "vacuum secondary" but this is an incorrect usage of the term.

The 1967 carburetors which I have seen are stamped with the identification number on the edge of the mounting flange. Assuming the carburetor is mounted on the engine; one may observe the number by leaning over the radiator and looking at the front edge of the flange to one's left. The number will be 4 digits, followed by the letter "S" (as in Sam). A 2 or 3 character date code may also be present.

The general rules for migrating a carburetor to a setup with a different transmission, but same engine make, size, and degree of tune:

(1) A carburetor originally designed for use with an automatic, may be used on a vehicle with a standard transmission, albeit at slightly less fuel economy than the correct carburetor.

(2) Attempting to use a carburetor originally designed for a standard transmission on a vehicle with an automatic transmission WILL result in idle issues, and MAY OR MAY NOT result in leanness throughout the entire RPM range, unless modifications are done.

Getting back to the definition of "vacuum secondary". Those carburetors that are truly vacuum secondary have a large (normally external) vacuum diaphragm which is connected to the secondary throttle shaft. Vacuum applied to this diaphragm controls the operation of the secondary side of the carburetor. Both Holley and Carter used the large external diaphragms; the Autolite 4100 uses an internal diaphragm (on the end of the carb). Wish I had a nickel for every reference I have heard about an "Autolite double pumper".

Many of the early 1960's Pontiac AFB carburetors did NOT have the stamped number, and were identified by the number on the tag.

This reference http://www.thecarburetorshop.com/Carburetor_ID.htm will aid in locating identification numbers on carburetors.

Jon.

When I look down the secondaries and pull the throttle (engine not running), the secondary blades appear to stay shut. I had always equated that with 'vacuum secondaries'.

My trusty '67 Pontiac Service Manual shows that there are actually two sets of valves in the secondaries. At 42 degrees of primary opening, the lower secondaries start to open - they reach full open when the primaries do. The auxiliary valve, located above the secondary, doesn't open until air flow pushes it open. That's why I couldn't see the secondaries moving with the throttle.

Fascinatin'. Thanks for the info, Jon.

Good info.Thanks Jon!

Jeremy