OK...I just picked up a 400 crank today that came with the harmonic balancer. Can anyone tell me specifically what the difference is between internal & external balance?? I did notice there is a partial "groove" in the harm. balancer.
Thanks!
Chris

That's the difference.

Internal balance means all the weight compensation for the rods & pistons is done by way of the counterweights on the crank inside the engine. External balance means that some of the counter-balancing needs to be done by way of weights on the balancer and/or flexplate on the outside of the engine (400 uses both). This is usually becuase there simply isn't enough room inside the engine to fit counterweights that are big enough and in the right place to properly balance the rotating assembly so they need to start sticking them on the outside parts that spin with the crank.

OK....I thought it was much more extreme than that (picture the counterweight from a Mazda rotary engine). So it looks like I need to find the correct flex plate, too.
Thanks!
Chris

A 400 has a raised area part way around it's balancer whereas a 454 has a knot up inside it's balancer on the back side that you can feel for to verify it is a stock balanced 454 motor..

I have gotten down on my back and slid under the front of the car and reached up and fingered for the knot.... Between the pan and balancer sorta deal....

I have asked but as of yet haven't gotten an answer as to how to visually tell the difference between a STOCK 400 and 454 flywheel?????

I have all three large flywheels, but my 454 is an inexpensive aftermarket jobber whereas my 350 and 400 are both stockers...

pdq67

[This message has been edited by pdq67 (edited June 03, 2005).]