I got a TCI Turbo 400 in my Coupe now for 23 years and it's been beat on almost daily and on the drag strip to ... I love it.
Since this thread was awakened from a nap I'm gonna chime in again, about OD yes or no. OD is nice. We're all conditioned to OD now from our trucks n daily drivers. WTF did we do until the late 70s when OD became the thing? We ran axles 3.31 and numerically lower. That 2.48 1st gear in a 400 takes the sin away from "highway gears" in a light car. Big sedans ran 2.78s, some even had taller than that. Take away 2000#. I did say dinosaurs are kool tho so there's that...
While on the subject of TH400, can some members please post how they configured a WOT switch? I've looked at some ideas of how they use ones for NOS systems but my twin Holley 600s have electric chokes so the back barrels throttle shaft idea won't work.
I’m toying with the idea of a momentary switch on the shift lever. Any other ideas? I didn’t really want to muck up my 3 deuce set up. I also don’t want to muck up my shifter either
I made up a home brew switch using a pull/on type motorcycle brake light switch and a cable slider fitting on the carb. With an adjustable stop on the cable I can adjust where I want the switch to activate. I have a spring on the switch that allows for throttle movement after it's been activated.
The stator in the Turbo 400 converter changes that 2.48 to a more performance friendly 5:1..... The Super Hydra-matic came with a 3.97 first gear because it didn't have a torque converter. My all time favorite is the 64-66 Buick Oldsmobile switch Pitch converter.. https://www.pontiacstreetperformance.com/psp/Twisting.html
I thought about that, I'm just concerned I might kick it or something since my pedal pivot is at the firewall instead of on the floor. I attached a picture of one I like, but my carbs have vacuum secondaries and electric chokes. My throttle shafts for the back barrels are somewhat inaccessible with additional hardware.
I also used a pull type switch connected to the carb throttle lever with a spring. It is a NO switch that I mounted in a small box (the black box in the picture) and then filled the box with epoxy to weather proof it. It is on a pedestal that is located by one intake bolt. It is sturdy and works well. However, the engine is a 401 nailhead and it is in a Model A. So far it accelerates quite well in high gear without needing to use the kick-down feature.
That's a option to run taller rear gears, but then we lose some performance off the line, and still cruise at fairly high rpm's at freeway speeds. One of the reasons cars began to get higher mileage before needing rebuilds is the low rpm's cars with an OD trans allowed. And no sacrifice in low end performance. I still run a non overdrive trans in my Austin gasser, just because it's not a long haul highway cruiser, so my 3.73 rear gears are fine for local 55 mph freeways, and around town. But I went OD on my '39 because I take it on long trips, and with 3.73 gears it still cruises at around 2100 rpm's at 65 mph. Makes it a much more useful car to go on long trips with.
Later model GM vehicles with TH400s had a k/d switch under the dash which contacted the accelerator pedal lever. It is (or was) GM #1242101. For the life of me, I don't know why I have that number memorized. https://www.ebay.com/itm/2847011684...1291&msclkid=a42d5dcc4cfb1b67308539faba14778d Depending on your pedal mounting you may have to fab up a bracket to mount it.
When I built my first car (32 Ford Roadster 1980)with a 400 turbo. I didn't use a kick down switch. I just pulled the shift levee down and hit the gas. Didn't know any better, also did something different, just looped the trans cooler line and drove it all over the US with no problems. I must of been lucky??????
@ClayMart , I was going to bring up the pedal mount, but you already did, with a link as well. I probably have that switch in my shop somewhere, but I misplace the tools I'm using now, can't imagine trying to find a switch that is "somewhere" here!
When my dad put the TH400 in my pickup, he used the pedal assy from the Vette. It has the kick down switch mounted on it. Doesn’t have a “vintage look” though. I’d bet bet GM didn’t just use it under the pedal as a Vette only thing.
This is where the Switch Pitch 400 is perfect. It's a poor man's overdrive. And no computer! Now to just find one!
The pedal mounted switch I mentioned above was used on the more common GM TH400 equipped cars as well as trucks, if I remember correctly. Probably thru the 70s and a bit into the 80s. The same switch was also used on some O.T. Z/28 Camaros to open the air flaps on the cold-air induction hoods. Maybe that's why the part# was still stuck in my giant brain.
I read your post, but didn’t realize you were referring to the pedal switch that could be used, I had thought of it as one assy (pedal and switch, etc). Good call.
In my moddel A RPU I run a 425 nailhead with a switch pitch T400 tranny. I have the kick down and the switch pitch wired to a 3 way toggle on my shift leaver. It works quite well.
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