Vortec swapped -88 with Edelbrock ProFlo4: No converter lock-up

[2JHead]

Hi

I have a -88 C1500 with a L31 crate in it with Edelbrocks ProFlo4 system. Stainless headers and single 3.5" ss exhaust. I built it last winter and have been enjoying it alot over this summer.

One loose end though: lock-up don't work.

When I installed the engine i basically cut off all of the TBI sensor wiring from the old engine back to the firewall - figured I didn't need any of it with the new injection system.

I suspect that the old computer controlled the lock up? Can I make do that again? what does it need? MAP?

JT

 

[b454rat]

Being it’s a 700r4, don’t need a computer. Could use a toggle switch, turn it on/off when you want, or could get a kit that does it automatically.

 

[PlayingWithTBI]

Could use a toggle switch, turn it on/off when you want

^^^X2 - I would wire in a relay with a momentary push button (and light) wired through your brake pedal so, if you have to make a panic stop or forget to turn it off, it'll release automatically.

 

[Dropped88]

They also make a kit for the lock up to work hydraulically and you can get rid of the electrical part permanently

https://www.oregonperformancetransmission.com/product/TRG-700-LU.html

 

[Erik the Awful]

I switched to a Holley Sniper, and I've been looking into this as well. You need a pressure switch, a vacuum switch, and a relay.

You can buy a kit:
https://www.speedwaymotors.com/TCI-Automotive-376600-Lockup-Wiring-Kit-2004R-700R4,334135.html

Or you can buy two switches and a relay and wire it up yourself.
Vacuum Switch
https://www.summitracing.com/parts/tci-cmp3766b
Pressure Switch
https://www.summitracing.com/parts/ado-8643710?rrec=true

IIRC the pressure switch goes in the 3-4 pressure port, which may or may not be tapped on your transmission. It's normally open enables lockup when it gets third or fourth gear pressure. The vacuum switch is normally open, and it enables lockup whenever you have high vacuum (i.e. part-throttle cruise).

Note that I haven't done this yet on my truck.