Brake switch for a 57 with an Lt1

[57kansastruck]

I installed an LT1 with 4L60E in my 57 Chevy 3100 short bed. I started it last week and I'm buttoning up the loose ends before I paint it . The computer raises the idle slightly if the transmission is in gear. Or if the brake is pushed. The stand alone wiring includes a brake switch lead. It requires positive power to the computer, until the brake pedal is depressed. This let's the computer adjust the idle if the brake is applied. The instructions ask that you tie the lead to the brake switch, sending positive power to the computer until you push the brake pedal. This is opposite of the way the switch works. The instructions say that older vehicles may need a different brake switch to work. I'm using a new four wheel disc brake master cylinder, under the firewall with the shortened stem stock pedal. Anyone out there ever done this? Any idea what switch I could use? Thanks in advance. Jason

[ricott]

General motors makes a "two" way brake light switch for cars with this type of tranny. I used a Brake switch from a 2000 camaro for a project I did like this. The switch is almost the same as early switches, and should screw in where your current switch is. Good luck.

[57kansastruck]

Thanks! I looked into that switch. I may try it. But my factory switch screws to the engine side of the firewall. The Camaro switch is completely different. Any other ideas out there?

[57kansastruck]

I think I may have found a way to wire in a relay to retain the factory brake switch. Lt1swap.com. I'll try it. Well if it warms up again this week. Jason

[mr48chev]

Cool, I was going to suggest rigging up a totally separate switch for the computer under the dash much like the later models have. Let the original switch work the brake lights and let the add on switch work the computer. The relay might be a lot simpler though.

[upon1]

I used the factory switch on my 55 with a relay and it works good and looks original.

[57kansastruck]

Thank you! I'll try this. I picked up a relay today and ordered a new switch to replace the crusty old one. Jason

[_Ogre]

i needed the same thing for my cruise control, i wired a relay into the brake circuit.
wired this way terminal 30 is hot, 87a is NC (normally closed) so it will be hot too.
when the brakes are applied, the relay energizes and opens 87a

[57kansastruck]

Ogre is exactly what I had in mind. I greatly appreciate it. One question: the diagram shows the hot lead to the relay before the switch. Does it matter that this lead is constant on and not hot with the key? I think the brake lead is hot all the time? The diagram I found online shows this as a hot lead with the key. Thanks! I'll copy this and use it.