400sbc to powerglide - Impala Tech
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post #1 of 6 (permalink) Old 08-27-2017, 01:48 PM Thread Starter
Join Date: Aug 2017
Posts: 6
400sbc to powerglide

Hello all, thinking about setting some time aside this winter for my 64 impala conv that has been waiting patiently while other projects took priority. I have built a mild 400sbc with camel hump heads, demon carb, and a mild crower cam and full length hedmans. I would like to bolt this engine to the freshened 2spd glide in the car. What I need to know is what size flexplate and converter will bolt up for this project, I will be purchasing both of these new. Thinking around a 2200 stall should be sufficient. This car is sentimental, and will not be sold as long as I am alive so not concerned with value or keeping it original. Thanks for any tips in advance.
BcSBC64 is offline  
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post #2 of 6 (permalink) Old 08-27-2017, 02:59 PM
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Welcome to the Team!

PowerGlide out of a base V8/six cylinder will not survive behind a big block. You have to think of your SBC 400 as a big block because it is already bigger than a 396. You need a TH400 or a PG built to handle your engines torque. The PG trannies you see in dragsters are a PowerGlide in name only: there are no Chevrolet parts inside the Super Bell heavy duty case. Many people think because they are used in drag racing that they are a strong tranny which is not the case. They can be built to be strong, but not with stock parts. PG's are used in drag racing because they only have two gears and when you are covering a quarter mile in just over six seconds that is all the time you have to get tires spinning and the car rolling. Most shift out of low in the first 100 feet off the line.

For the street you want more gears, even with a big inch small block. A TH400 or a BUILT 200R4 is the ideal choice.

But to answer your question you need an externally balanced 168 tooth (14" inch in diameter) flex plate for your 400; unless it has a forged internally balanced crankshaft in which case any flex plate you can find will work. That big of a diameter will not fit in a PG case for a SBC or a six that had a 153 tooth flex plate. You could saw off your stock bell housing with a hack saw blade and bolt on a Super Bell to your PG's front pump bolts to clear the bigger flex plate. Just remember the SBC 400 used the high torque stater off of the BBC (168 tooth starter ring) so your stock 283-327 starter won't work either.

Big Dave
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post #3 of 6 (permalink) Old 08-27-2017, 06:08 PM Thread Starter
Join Date: Aug 2017
Posts: 6
Thanks Dave. I don't really plan on rodding this thing around but possibly a th400 might be a better plan, just sucks doing driveshaft, linkage, mounts and whatever else may be hiding in there.
BcSBC64 is offline  
post #4 of 6 (permalink) Old 08-27-2017, 09:50 PM
Join Date: Jun 2017
Posts: 25
The Poweglide will work fine in your application. The manufacturer of whatever torque converter you choose will tell you what flexplate you need to mate with that converter. Make sure that you communicate clearly that you have a 400ci SBC. The 400 takes an externally balanced flexplate that is different from a 283/307/327/350 flexplate.
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post #5 of 6 (permalink) Old 08-31-2017, 12:58 AM Thread Starter
Join Date: Aug 2017
Posts: 6
Thanks Mike. I think the wife will drive this car more than I will. I have a 79 Malibu with an angry small block that is more for adrenalin ?
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post #6 of 6 (permalink) Old 09-01-2017, 06:22 AM
Join Date: Jul 2016
Posts: 84
If you don't pound on it too hard the PG will be fine. Agree totally with Mike.
rbwinston is offline  
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