72 Cutlass, TH350 to TH400 Question

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Old Dec 21, 2019 | 10:40 PM
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72GoldOlds350's Avatar
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Question 72 Cutlass, TH350 to TH400 Question

As the title states, I have a 1972 Cutlass. The engine is going to be a built SBO 350. Car currently has a TH350 but a TH400 is going in.

I have everything ordered with exception of the wiring harness for the kickdown switch. My builder stated "I researched the kick down switch harness it looks like we will need to make a Chevy one work since on the Olds its part of the main harness."

Is this true?

I should have everything else. I ordered everything via this thread: https://classicoldsmobile.com/forums...-th400-135919/
Old Dec 22, 2019 | 06:21 AM
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There are vendors who sell just the wire with proper molded end. All you need is a series 56 male terminal, some orange wire (16 gauge I’m guessing) and a sealed female 1/4’ female quick disconnect. The service manual will tell you which cavity to insert the 56 terminal.
Old Dec 22, 2019 | 06:26 AM
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There are many aftermarket kickdown switch setups for GM that hook to the carb linkage, find one you like. Then all you need is to hook up keyed power to one side of the switch and from the other side run a wire to the transmission. The one below is simple and not expensive.
An article with additional pictures:
https://www.hotrod.com/articles/hppp...witch-install/


Old Dec 22, 2019 | 06:40 AM
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Originally Posted by 72GoldOlds350
My builder stated "I researched the kick down switch harness it looks like we will need to make a Chevy one work since on the Olds its part of the main harness."

Is this true?
Yes, that is true. The TH400 wire is built into EVERY Cutlass harness in 1972, which means that the harness already installed in your car already has it. Typically it's taped up to the rest of the harness under the hood, and the connector for the switch on the accelerator should already be under the dash. There should be no need to buy anything.

You are aware of the differences in the e-brake cables, right?
Old Dec 22, 2019 | 10:07 AM
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72GoldOlds350's Avatar
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Originally Posted by joe_padavano
Yes, that is true. The TH400 wire is built into EVERY Cutlass harness in 1972, which means that the harness already installed in your car already has it. Typically it's taped up to the rest of the harness under the hood, and the connector for the switch on the accelerator should already be under the dash. There should be no need to buy anything.

You are aware of the differences in the e-brake cables, right?
Yes, I am and have the new e-brake cables ordered. Thank you.
Old Dec 22, 2019 | 10:12 AM
  #6  
72GoldOlds350's Avatar
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Originally Posted by matt69olds
There are vendors who sell just the wire with proper molded end. All you need is a series 56 male terminal, some orange wire (16 gauge I’m guessing) and a sealed female 1/4’ female quick disconnect. The service manual will tell you which cavity to insert the 56 terminal.
Thanks! Any links?
Old Dec 22, 2019 | 07:11 PM
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https://www.summitracing.com/parts/a...CABEgL5TfD_BwE

https://www.autopartsandcollectibles...=113&mode=prod

https://theelectricaldepot.com/weath...als-br-25-pack

Last edited by matt69olds; Dec 22, 2019 at 07:13 PM.
Old Dec 22, 2019 | 07:39 PM
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coppercutlass's Avatar
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How much power what's wrong with the th350. Im running high 11's with a th350 that I bought used that lived behind a 455 that powered a 76 lemans into the mid 11's just curious.
Old Dec 23, 2019 | 07:20 AM
  #9  
72GoldOlds350's Avatar
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Thank you!

Originally Posted by coppercutlass
How much power what's wrong with the th350. Im running high 11's with a th350 that I bought used that lived behind a 455 that powered a 76 lemans into the mid 11's just curious.
530hp/580tq

The stock TH350 is already trashed.
Old Dec 23, 2019 | 08:10 AM
  #10  
coppercutlass's Avatar
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The th350 can be built to handle the power . the th400 although stronger in stock form will need work. The difference is th400 will eat up some HP.
Old Dec 23, 2019 | 07:06 PM
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72GoldOlds350's Avatar
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The TH400 is already built, it isnt stock.
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