Internally or Externally balanced?

[Dave22443]

Okay, let me be up front about this.  I have a non-numbers matching '68 Charger with a 318 in it that I am building into an R/T Clone.  I have reason to believe that the car may have been raced at one time *many* years ago before I bought it.  For example, there is evidence of it once having a drive shaft loop installed, the rear gears appear to be "sure grip" and of a very low ratio (3300 RPM's @ 55 MPH) and accourding to the VIN tag, it was originally a 383 HP 4-bbl car.  (There is also an extra unused bracket underneith which appears to have been for a clutch pedal, although the VIN says Automatic)

I have purchased a 1969 Plymouth 383 Super Commando with automatic transmission that I am getting ready to transplant into it and I have a few questions. At this point, no, I don't really care about numbers matching - I'm a poor man who just loves owning a classic Mopar! 

1) When considering a new Torque Converter, would I say that this engine is internally, or externally balanced?

2) Are all big block mopar transmissions 727?  If not, how can I tell what I have?  If it helps, I found some numbers on the bell housing that are about 2 inches tall.  They are 176-3

3) When pulling a small block out of a B-Body and switching to this big block engine, what kinds of problems will I run into with the drive shaft?  For example, are the yokes a different size?  What about length?  (hint: I don't know what my small block tranny is either.  It's number is 764-5)

4) What do you guys think about the fluid filled harmonic balancers they have out there?  And what would having one do for me?

5) Given my 3300 RPM's (measured from a cheap after market tach) @ 55 PMH (measured with a hand held GPS), what would you guess my rear gear ratio is?  (tires are P235/60R-15)

  Thanks!  Here's what the car currently looks like.  I spent all last winter fixing it up and painting it.  This winter is upgrading the mechanicals.  I converted to front disk brakes last week and pulled the 318 out yesterday.  Now I'm detailing the engine compartment before putting the 383 in.

[Blown70]

You need to know what motor you are using.  The tranny will not matter internal or external....  Flex plate will matter.

CUDA ken will help with the Gears.... I would have to spin the drive shaft and count the tires.

TOM

[Dave22443]

The motor is a 383 Super Commando pulled from a 1969 Plymouth.  Its bone stock.

[Blown70]

I am sure those are internal......However I do not know 383 at all.  Sorry.  However we do have some RESIDENT experts for you they will post for you.

Tom

[Charger_Fan]

4) What do you guys think about the fluid filled harmonic balancers they have out there?   And what would having one do for me?

I have heard a few times that harmonic balancers like "Fluidampr" & "The Rattler" , etc. aren't as good as they claim...something to do with the dampening weight not staying in one spot all the time. So as a result, I haven't used one.

[Khyron]

Only motor I know of being externally balanced is a 360....

and of course, I would have that…. Damnit

[firefighter3931]

The motor is a 383 Super Commando pulled from a 1969 Plymouth.   Its bone stock.

Dave, that engine is internally balanced. You want a neutral balance converter for this combo if you decide to swap it out for something with more stall. Summit Racing carries a line of balancers that are excellent quality and cheap. Yours might be fine. Stock balancers can also be rebuilt.

Ron

[71440se]

i would say  you have around a 430 rear gear in there. go on ebay and check out the imported balancers they are starting around 65$.

[694spdRT]

Only motor I know of being externally balanced is a 360....

and of course, I would have that…. Damnit

The later cast crank 400's and 440's are also.

[Chryco Psycho]

1[ I agree the engine is internally balanced
2] all big block autos are 727 trannys
3] if the small block 727 is in the car now the driveshaft will be identical , if it has a 904 now the driveshaft will need a larger yolk & 4" approx cut off
4] Fluid Dampers have less inertia initailly & allow the engine to rev faster really though they are a race piece & are overkill on a street engine
5] if your tire is approx 26" dia I make the gear ratio to be 4.56
good looking Car !!

[Dave22443]

Thanks ChrycoPsycho, that helps a lot!

After pulling the 318, I test fit the old yoke into the new tranny and it doesn't fit.  I assume then that the old tranny is a 904, which is what I suspected anyway.  I also noted that my drive shaft has two different sized universals in it, suggesting to me that someone already modified this drive shaft to fit the small block.

I do have a big block drive shaft that I saved out of a wrecked 1965 Newport.  Its yoke does fit and it's the same length as my current drive shaft, but from what you say, it sounds like it may be too long.  Looks like I'll be looking for a good welder to make one good from two bad.

Thanks for all the info guys.  You've been a great help!