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Discussion Starter · #1 ·
I'm trying to connect or plug off the vacuum ports on my 1405 Edelbrock, but I'm confused about how they need to be connected...

I know one connects to the distributor but I don't know whether or not to plug off the second vacuum port or connect it to the transmission...
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A guy told me if the transmission has a lock up torque converter, then the vacuum port gets connected to the transmission, but if the transmission has a non lock up torque converter, I can plug the vacuum port up.

I have a TH350 transmission. I read that prior to 1980, these transmissions didn't have a lock up torque converter and after 1980 these transmissions came with lock up torque converters, and this could be identified by the TCC plug and wired connector on the drivers side of the transmission, prior to 1980 these transmissions didn't have this plug or wiring.
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Discussion Starter · #2 ·
Bought the car like this...

It shifts fine... So if it needs that plug and it's missing and I'm still able to drive it on the highway, what's going on here ?

Replaced the lock up torque converter with a non lock up and ripped away the connector and wires ?
 

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Your t350 or t350C needs manifold vacuum for the vacuum modulator. The need for vacuum has nothing to do with lock up convertor.
Your trans will work fine without the lockup hooked up. I bought an 84 c10 and drove it for a year like that.
The vac ports on the carb front are for the vac advance on the distributor. Either can be used. Depends what your motor likes. Put a cap on the one you don’t use.
The vac for the modulator normally comes from a vacuum tree behind the carb. The tree screws into the intake runner.
 

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Just some info to add....on swapping parts and converter between TH-350 and 350C variants. No go.

You can't use a standard input shaft, front pump, case, valvebody, or converter with a lock-up converter model, and vice versa. Major parts don't interchange and can't be swapped either. Only some of the internal parts are the same, along with common rebuild serviced parts have a lot of interchange....but the larger parts don't.
With that said about swapping parts out of the way....

You can run a lock-up converter TH-350C forever with the lock-up disconnected....it just never locks up for that last 1-2 miles per gallon of fuel mileage you could have been having.... but it won't hurt anything.

If you do decide to use it, it can be wired back up to factory spec, or it can be set-up with a manual 3-position toggle switch for the driver to activate and wired through a 3 post brake light switch to trip it back out of lock-up when you come to a stop.
(They stall the motor if you don't trip them out when using a manual toggle switch.)
 
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