More crankshaft curiosity
 

I have two crankshafts for my '88 7M-GE. They have the same sizes on all bearing surfaces and are almost perectly identical ,except every 3rd counter weight is in a different location. Which one is correct? Here is my poor artistic representation of what's cast into the two cranks.

I think as long as you are sure both are 7m ge , the location of the counterweights is of non importance..since they are placed on the crankshaft in order to balance them and since no 2 crankshafts are balanced the same...it would'nt matter....

I got my camera to cooperate for five seconds ,here's a pic...

It looks like there is more 'mass' on the crank to the right side of photo.

Where did you get 2 cranks??
Which is the one outa your car???

I believe I read somewhere (here, or SM forum) about a crank update in '89, that was for better balance, and less vibration.

Perhaps one of those is an updated version.

The one on the left is out of my engine ('88),the one on the right I bought used (exact year unkown) . All the tolerances are dead on and the working parts seem to be in the correct locations. That'd be nice if it is a lower vibration version.

Well Mr. Nickleye, I got this out of one of your threads in the FAQ's:

And I quote: In 1988 "Toyota began using the "7M" crankshaft mid-year, with dual counterweights to improve smoothness. The extra weight also caused the redline to drop from 6500 to 6250."

"The 86.5 Supra had a new block under the hood, although it used the crankshaft from the JDM MKII's 6M-GE"

So from 86.5-88.5 ALL supras came with cranks from MKII JDM 6M-GE's.

And from 88.5 on they came with true 7M cranks.

The crankshafts actually changed for the 89 model year. Half way through 89 they changed so if your car is an 89 it could have either. There were also different motor mounts half way through the year. Some early 89's also had the green plug harness. I've had 3 89's and all of them had the early version 6m crank shaft with gray plugged harness and square motor mounts. It was a grab bag kind of year.

^^^

That's why the dealer always asks what the production date or VIN is when looking up parts.

Toyota is a company that does not just sit still. It is always improving on things, even in the same model year.

building my engine as we speak, mine is a 88 turbo and my crank says 6M. If i remember it is in the front side (timing belt side) on one of the counter weights

The "new" crank has the 6M stamp on it ,so the junk one musta been a "true" 7m by just a couple months :P Silly toyota. Thank you so much everyone for your input.