383 to 727 help - 66 Charger

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ClarkDart70

ClarkDart70

Street Machines Limited
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Ok let me clear the air by stating this isn't my car. My friend just picked up a pretty raw 66 charger project that someone did everything to about 80% and moved on to something else. The biggest and first thing is connecting the TF727 to the 383, so we can get it running.
This appears to have once been a 318 car with a TF727 (My buddy ran the numbers and this is what he says, I don't know for sure). The last owner swapped in a 383 and the flex plate holes do not line up to the flywheel holes to mate the two.
So my question is, does my friend need a flex plate or a flywheel?
I am guessing a flywheel because the flex plate would be specific to the 383 while the 727 flywheel is currently for the old 318 small block and it will need swapped out to mate to the big block set up.

Anyone agree or disagree?
 
...............1st off the flex plate is used 4 an auto trans, is bolted to the engine...the converter has the ring gear made on it for the mopars.........there is 2 different flex plate bolt patterns as well as 2 converter patterns....as well the converters are different diameters.....which do u have on ur engine and which on the converter..........prolly easier to get a flex plater to match the converter, but u can do it either way.............kim..........
 
Also note the flexplate to converter pattern is not symmetrical. There is only one way to get all four holes to line up.
 
currently none of the holes line up. I have only looked into the problem at a 5 minute glance and its in the car currently. I think he would rather buy the flex plate beucase of pricing. We'll have to dig in more.
 
A flywheel is used on an 833 manual, a flexplate is used on the 727 automatic. I would say that if you can't get the asymmetrical bolts to line up that you need a new flexplate. Mind you, the 318 has an internally balanced converter and a 383 does not. You may need to change the converter as well, or maybe just the converter.
 
...............A 383 converter is internally balanced.....none were external,not even the cast crank 71 engines....kim..........
 
The 318 tranny will not mate up to the 383.You need a big block tranny,flexplate,and converter ...
 
You may have a 904 trans/ converter and a 727 flexplate, or vice versa
 
So a couple things for you and your friend to verify;

What was the original auto trans? 904 or 727 and was the flex plate used from the original small block crank? The flex plate from a small block will most likely (there are a few exceptions)bolt up to the big block crank regardless of the auto trans however the 904 flex plate is smaller and will not bolt up to the 727 stock converter. If the original auto trans was a 727 then the flex plate should bolt up to the 727 converter but as others have noted the bolt holes will only line up when clocked to the correct possition (you have a 1 in 4 chance of getting it right the first time!)

Verify the 727 to ensure the bell bolt pattern is correct as they are different for small block and big block (no stock 904's with big block pattern)

Verify that the 727 convertor is neutral balanced - no extra large weights welded to it (there may be small ones to balance)

The above not verified necisarily in that order lol

There may be other differences but I think these are the major ones for the typical years and assuming we know the engines in question are in fact 318 and 383 internaly balanced (I cannot recall if the 1971 383 cast crank engine is externally balanced or not)
 
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