Another converter lock-up question

[Sal Lubrano]

I am getting closer and closer to a finished product but not there yet. I am trying to get the lock-up to work properly in a non-computer car (carburetor). It is wired properly 12 volts ignition to the brake switch then to the 4th pressure switch and lastly to the solenoid. The converter lock up like a champ in 4th but it locks cruising at 40mph so when you try to accelerate the motor knocks until you put your foot in to it for a downshift to 3rd. So, I installed a vacuum switch n.o. 9" in series and it got much better but I have another problem now. The converter locks and unlocks great but there is a sweet spot when cruising at about 40 mph. The converter locks in 4th with high vacuum then I try cruising or very light acceleration. As soon as vacuum is low enough it unlocks but engine vacuum increases when it unlocks to higher than 9'' locking back again. And this will happen back and forth. Locking and unlocking. At this sweet spot. Is there anyway to fix this. I put a delay valve on but it does not cure the problem but tames it down.

 

[SSedan64]

One of the adjustable vacuum switches may be needed.
Look at the bottom of this page, there're several listed, 71V2 from PATC adjusts from 6-22".
Automatic Overdrive Transmission Swap

 

[77 cruiser]

That's why I lock mine manually, could never figure out the auto LU in 4th, unless you just get out on the hiway & go, I guess the it would be OK.

 

[Sal Lubrano]

so. how did gm get it to work correctly in the 80's. was lock up always computer controled from the start?

 

[overkillphil]

Sal, we use the good B&M lockup kit with most of our 200-4R conversions. Not the elcheapo one with the manual switch.

The one we use has a speed sensor that is installed between the speedo cable and the trans. Screws right in and has a control dial and mounting bracket so that you can adjust the speed that the convertor locks up between @20-90 mph, right from the driver seat. We wire it through a later brake pedal switch so that the converter unlocks when the pedal is tapped just like the later cars.

This is the best system we have found on the older carb cars so far. No problems and you can adjust it while driving if you want. I don't like the vacuum switches or the 4th gear pressure switch. We used that years ago and unfortunately the vacuum switches never seem to do what we want, when we want. The 4th gear switch locks the converter in OD whether you want it or not. Some cams really aggravate the lockup when it is at too low of an rpm. FWIW

 

[SSedan64]

Sometimes you can find them on Ebay cheap. I bought one several months back new for $40.

B&M Converter Lockup Controls
B&M, Torque Converter Lock up Kits - summitracing.com