TBI Question

[1980_Cj7]

Anybody know what the fitting on the bottom left of this setup hooks up to?

What you are looking at is a GM big block throttle body with the factory adapter that mates it up to a Quadrajet spread bore intake manifold. I believe that fitting is in a passage that is tied into the Idle Air Control Valve just above it, but unfortunately I don't have it in front of me. It's at a machine shop having an adapter made to mate it to our square bore intake. The machinist is asking me if he needs to incorporate that connection into the new adapter. I didn't pull it from the vehicle that it originally came on, so didn't get a chance to see what it was connected to.

I don't believe the adapters that are commercially available have anything like that fitting.

https://home.comcast.net/~rwsr50/ComcastOnlineStorage/TBI%20001.jpg

[cjmike67]

Looks to me like the TPS Throttle position sensor!And yes you need that !! :sa:

[76-cj7]

may be some sort of vac. port ???

[1980_Cj7]

The electrical connector on the right is the Throttle Position Sensor. The electrical connector on the left, the one that is broken, is the Idle Air Control Valve.

What I'm trying to pin down is what the treaded connection on the lower left connects to. (I know the big threaded connection on the rear center is to pipe coolant thru the adapter.)

[ironman_gq]

probably the connector for the brake booster. on the Qjets it is screwed into the back of the carb into a fitting like that one.

[tsanchez]

^^Correct it is for the booster. You don't even need the coolant ports just a plate.

[1980_Cj7]

Thanks guys, that's good to know. I wasn't planning on running coolant thru the new adapter like there is in the factory one, and since we have hydroboost, we don't need to worry about the brake vacuum line either.

With a small block TB, it would be real easy to make an adapter. It could be just a plate like tsanchez said. With the big block TB, it's a little more difficult though since the overall width of the throttle plates is wider than the opening in the intake. Need to make the adapter a little thicker and funnel shaped.

I was wondering though if I could just sit the TB on cockeyed/cornered so that the butterflies fit within the intake opening. I don't think it would create any problems linkage-wise since we are using a Lokar cable. I'll have to check and see if any of the linkage on the TB would end up hitting anything.