Converter lock-up

[Sal Lubrano]

Just finished getting the converter to lock up on a friends car. But we ran in to another problem. The car has a carburetor with no computer. We ran a 12 volt power to the brake switch and then to the converter solenoid then from the solenoid to the 4th gear pressure switch. The lock up comes on when the trans goes in to 4th. Here is the problem. If cruising at about 40 mph the converter locks and if you want to accelerate the engine is bogging down like driving a manual transmission and going to a too high of a gear too soon. Also on the highway you want to accelerate and you push the gas and get nothing until the downshift, then all of a sudden too much acceleration. I guess my only option now would be to install a part throttle switch somewhere on the carburetor linkage to unlock the converter when an acceleration is needed. Does anyone know of a way to do this? I know the wiring but to build the switch and design has me stumped. Maybe there is a company which has something for this already. He has an edelbrock 4 barrel. Thanks for the help.

 

[mikestertwo]

Hook an adjustable vacuum switch in series with the 4th gear switch. When the vacuum drops to a preset level the converter will unlock.

 

[Sal Lubrano]

mikestertwo Thank You. Much better idea than I had. Where would I find a switch like that?

 

[mikestertwo]

Where would I find a switch like that?

I can't remember where I bought mine. I'll check into it. The switch I use is a Hobbs (Honeywell) Part# 77343. You can also use part# 77345. The only difference is the type of wire terminal. The 343 has a screw termimal, the 345 has a blade terminal for push on connectors. The switch is adjustable from 1"hg to 22"hg and has contacts rated 8A@12V. Has a 1/8 NPT fitting to screw into the intake manifold.

 

[mikestertwo]

I just remembered where I bought my switch I ordered it from DIGI-KEY. It cost about $23

 

[Sal Lubrano]

Thank you very much. I am going to order it now. One last question. The factory brake switch was designed for the torque converter lock-up. From the factory was it operating a relay or was it direct power to the solenoid? I am guessing the lock-up solenoid can't be more than an amp?

 

[Sal Lubrano]

Just searched that part number and it brought up the correct part but the it was not adjustable. It brought up 3 different ones with the same number but with different ratings. 2, 4, 9" HG. ? I will probally call them. That part looks perfect.

 

[Sal Lubrano]

Just ordered it. They come from the factory preset to those settings but they are fully adjustable. Thanks again.
Sal

 

[mikestertwo]

The factory brake switch was designed for the torque converter lock-up. From the factory was it operating a relay or was it direct power to the solenoid?

It's wired direct. No relay.

 

[Sal Lubrano]

You mention screwing it in to the intake but using a nc switch it would need ported vacuum from the carburetor? If I used a no switch hooked up to manifold vacuum it would close under vacuum until the manifold dropped enough to open the switch? Could you explain how yours is done please.

 

[charlief1]

Cool info. Thanks guys.

 

[mikestertwo]

You mention screwing it in to the intake but using a nc switch it would need ported vacuum from the carburetor? If I used a no switch hooked up to manifold vacuum it would close under vacuum until the manifold dropped enough to open the switch? Could you explain how yours is done please.

I think I gave you the wrong part# for your application:redface: On my setup I was going through a DPDT relay. I was using the N.C. contacts on the relay for the converter. Sorry I wasn't thinking. For your application it would be simpler to use the N.O. version part#77342