Quadrajet Ports: Manifild or Ported Vacuum?

[G_RIDE_81]

Good day! So, I have a Q-jet #17085204 (emissions carb) on an '84 Monte Carlo. Original equipment to the best of my knowledge. I'm in process to swap in an MSD Atomic TBI in the smog-legal set-up. The Atomic has 1 ported vacuum and 4 manifold vacuum ports. My question is:

Per the Q-jet carb vacuum diagram, which ports are manifold and which are ported vacuum?

N
J
B
L
 M
T - N/A (fuel bowl vapor, will no longer be use and will be capped at the canister control valve)

Thanks in advance.

 

[G_RIDE_81]

Per the Q-jet carb vacuum diagram, which ports are manifold and which are ported vacuum?

So, I've researched a little via other forums. Some people say that M is the only ported vacuum port. Is this correct?

Also, some people say that some of the front ports are "metered manifold vacuum." What does that mean and how does that work?

The new Atomic only has full manifold vacuum ports. What problems could I encounter without "metered manifold vacuum" port options? Would using a check valve of sorts help?

 

[jcelk]

before you pull the carb check the vacuum ports the manifold vacuum ones will have vacuum at idle the timmed or ported ones won;t have vacuum at idle they only have vacuum at higher rpm

 

[Clone TIE Pilot]

Ditch the TBI and stay with the Qjet. The stock low emission systems in your car are designed for carburetors, not TBI. You would need a low emission setup from a TBI engine. Even then there are legality issues in Frankensteining various different low emission packages together.

 

[G_RIDE_81]

before you pull the carb check the vacuum ports the manifold vacuum ones will have vacuum at idle the timmed or ported ones won;t have vacuum at idle they only have vacuum at higher rpm

Too late. I'm on the middle of the swap. Already pulled the carb, remove and blocked off the mechanical fuel pump.

 

[ELCAM]

J, T and M are ported vacuum.

 

[Clone TIE Pilot]

Keep in mind that E-Qjets and TBIs use different styles of charcoal cans.

 

[G_RIDE_81]

You would need a low emission setup from a TBI engine. Even then there are legality issues in Frankensteining various different low emission packages together.

Oh wow, interesting. I hope this not the actual case. And agreed, Frankensteining is a headache I don't want. Thanks for your input.

ELCAM provided a good update. Fingers crossed.

 

[G_RIDE_81]

Keep in mind that E-Qjets and TBIs use different styles of charcoal cans.

The way the Atomic is marketed this shouldn't be the case. I need to look into this. Thanks for letting me know.

 

[G_RIDE_81]

J, T and M are ported vacuum.

Every resource agrees on M being ported, game!!

J and T are the ports that someone described as "bleed off manifold vacuum." Them being ported vacuum makes more sense, right?!