opinion re crankshaft

[robmog]

After splitting my case i found my 2.4 crank has been reground to first undersize (.25).
Should i reuse it or try to get a used STD/STD crank?
i have no info on the regrind but the bearings are dated "82"
any opinions?
bob

[MBruns]

The availability and/or the price of bearings in non std sizes is getting tough, the ground crank is not a big deal for a street engine as long as it was re heat treated.

Mike Bruns

[robmog]

mike,
i don't know if it was rehardend, that's the big question. i know the car was driven for 10 years after the first rebuild and the crank bearing surfaces look good, no scoring and in spec with proper chamfers on the oil holes.
so, i think it was done right but can't be sure. you're right about the bearings though. $450 for a set from our host vs $125 for standard.cranks seem to be in the $5-600 range so for the differance of $150 i get a "virgin crank"
anyone else got an opinion?
bob

[Eagledriver]

If it worked fine for 10 years there is no reason to believe it will not work for 10 more.

-Andy

[MBruns]

I agree if the journals look and measure OK than most likely it was treated, they are soft when ground without, The air cooled parts are going out of site and especially the odd items, I have bought strong std cranks in the 300.-500. range so its kind of a wash, those cranks have had some problems with breaking in two, so if yours looks good and you can find brgs. I would go back with what you have being you know the history.

Mike Bruns JBRacing.com

[robmog]

thanks mike and andy,
bob

[304065]

Rob,

My crank was reground in 1982, .50 under on the rod journals. I don't know why, I assume it was excessive ovality. In any event, I measured the crank to the best of my abilty, and decided to re-use it. My measurements are in this thread: Measurement, Instruments and Metrology

Obviously your measurements will be all different both in terms of the journal diameters and the regrind, but you get the idea. Measure, graph, then sit back and analyze.

Even if you get a "std/std" crank this is a good idea. The fact that a crank has never been reground only means the surface hardening is intact, it could still have wear you deem unacceptable.

I just received my crank back from the local machine shop. I had it magnafluxed first (no sense working on a junk crank) and then micropolished and cleaned, then balanced. The balance was within factory specifications so no metal was removed.

I will measure the bearing clearances just to be certain. In my case, the undersize bearings for the rods were about the same price as standard. Not so for the mains, though.

Good luck!

[robmog]

john,
i checked my rod bearings and they're .5 under too.
so now i'll need .25 U main and .5U rod bearings.
a used standard crank might be the cheaper way to go!
standard main + rod bearings = $270
.25u main + .5u rod bearings = $740!
btw great thread on measuring.
operation overkill lol
i now alternate between rust repair and staring at engine parts.
thanks for your input.
bob

[kucharskimb]

PM