1973 Formula 400 Quadjet Connections - Second Generation Pontiac Firebird (1970 - 1981) - Firebird Nation

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1973 Formula 400 Quadjet Connections


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3 replies to this topic

#1 CBJoe

CBJoe

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  • Gender:Male
  • First Name:Joseph
  • City:Indianapolis (MARION)
  • State or Province:IN
  • Country:USA
  • Year: 1973
  • Make: Pontiac
  • Model: Firebird
  • Engine: 400
  • Transmission: TH400

Posted 2 weeks ago

Long story short I picked up a 73 Firebird Formula 400 that had a damaged Buick Quadrajet Carb on it.  All the vacuum lines are wonky and not standard...so I have no baseline.  I sourced a year correct Hot Air Choke Pontiac Quadrajet and am in process of installing.  I need some help ensuring I connect the Vacuum hoses correctly.

 

All EGR and Emissions have been removed by the time I picked up the car.  They just aren't there....

 

Only Vacuum Connections I "think" need to be connected are the following:

 

- Brake Booster (Currently connected to lower rear of Qjet)

- Line to firewall...which I assume is for HVAC (Currently Connected to top rear of QJet)

- Vacuum Advance on Pertronix HEI distributor (Currently connected on the lower front right of QJet)

- Vacuum Line to TH400 Transmission (????? - I planned to connect to same direct intake vacuum port use for brake booster w/ splitter)

 

I'll post pics tomorrow, but if anyone has quick feedback it would be appreciated.

 

Cheers, Joe

 

 

 

 



#2 JoePeek

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  • Year: 1971
  • Make: Pontiac
  • Model: Trans Am
  • Engine: 455 HO
  • Transmission: 4 speed

Posted 2 weeks ago

Everything looks OK, except maybe the line going to the HVAC. If it is high up on the carb, it is most likely ported vacuum. I don't have AC in my 71 TA, but I'm thinking if it needs vacuum to move something, it should be able to function at idle .....which means using direct manifold vacuum. As far as vacuum going to the distributor, some engines like direct vacuum, some do better with ported. To be sure if the connection is direct or ported, you should get a vacuum gauge to verify. That big connection going to the brake booster is for sure direct, and the transmission needs direct vacuum as well. If you get good vacuum at idle off a connection, it is direct. If you have to rev the engine to get vacuum, it is ported.



#3 CBJoe

CBJoe

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  • Gender:Male
  • First Name:Joseph
  • City:Indianapolis (MARION)
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  • Year: 1973
  • Make: Pontiac
  • Model: Firebird
  • Engine: 400
  • Transmission: TH400

Posted 2 weeks ago

Excellent...Thanks Joe.  I do have a vacuum gauge...so I'll verify where everything goes.  I actually have a Dual port connector on order that splits the rear connection and i'll run one to the transmission and one to the brake booster.  

 

Gonna try and get it all started up and checked this afternoon.

 

JoeS



#4 CBJoe

CBJoe

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  • Gender:Male
  • First Name:Joseph
  • City:Indianapolis (MARION)
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  • Country:USA
  • Year: 1973
  • Make: Pontiac
  • Model: Firebird
  • Engine: 400
  • Transmission: TH400

Posted 2 weeks ago

All Seems well. I read around 18-20" Vacuum at idle on the full vacuum ports.  I did find out that the Pertronix Digial Distributor I have requires metered vacuum. I verified the port is indeed metered where I have it plugged in.  So AC/Trannsmission/Booster are on full vacuum and the Distributor advance is on metered.  

 

So thats done...now on to figure out whats funky in my dashboard electrics...I think I may have a bad ground.  as I operate the different turn signals, headlights, and flashers, the gauge needles all fluxuate and drop in and out.

 

Cheers, Joe






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