IDing a vacuum/mechanical secondary

[fireplug]

I'm absolutely carb illiterate! I have a Q Jet well two actually. How do I identify between the two? Also is there a way to ensure the cfm? I'll assume an electric choke will have a wire going to it?

Yeah I know starts with N ends with oob

 

[Bent77]

Most Q jets are mechanical on the manifold w/ the vacuum controloing thr top when the metering rods are attached. The vac controlled ones should have 2 vac bells where a standard only has one.

Your best bet is to go to the library and rent a book by Doug Roe called "Rochester Carburetors" the theory is the same for the Carter built models.

 

[Blue85]

Q-Jets are kind of "variable cfm". That's why you can run an 800cfm Q-Jet on a 350 with no problems while a Holley or Carter 800 would be way too big.

Typically the throttle blades are all controlled mechanically. The linkage makes the primaries open a lot before the secondaries start. Then the airflow through the secondaries pulls the big flaps on top of the carb open. This also moves the secondary metering rods for enrichment. You should be able to easily flap these open by hand, work the throttle linkage and see the secondaries open at the bottom. You will probably have to open the choke by hand because most Q-Jets lock out the secondaries when the engine is cold.