Safe Crankshaft journal sizes.

[mpbiv]

I have a cast crank from a "remanufactured" 88 TI engine that I am trying to use for my new engine buildup. I don't know who remanufactured it but it does have a "reman" tag with a serial number on the block above the water pump housing. Its a pretty clean engine, and is in good condition but everything has pretty much been machined to the max. I found out recently that the cylinders were bored .040" over (and it has cast pistons of unknown manufacture).

Well today I took the crank out, and mic'ed the main and rod journals. It measured 1.9399" on the rod journals and 2.3319" on the main journals both with spot on repeatability over 4 measurements. The standard specs I have are 1.969" and 2.362" for the rod and main journals respectively. Maybe someone can verify that these are the correct standard numbers.

Assuming I am thinking correctly that means both rod and main journals were machined .030" undersized. So I would need .030" oversize bearings. I checked FWD Performance and they only carry up to .020" oversize bearings which threw up a red flag in my mind.

If I could find .030" oversize Clevites somewhere else should I use this crank? Or should I be looking for another crank? Experienced opinions appreciated.

Thanks,
Maurice

PS-I am building a 2.2 shortblock using an 88 TII block, TII rods w/ARP bolts, Mahle .020" TII pistons. I want this shortblock to handle 250-275hp without having to worry if the crank will be a weak link.

[mopar2ya]

Im running a R/T with a 40/40 forged crank at a bit over 400 h.p. .040 was as big a bering as FWD could get. SO far so good.

[mpbiv]

Thanks for your input Wallace

My boss (I work in a college machine shop) also brought up a few other concerns. Are these cranks nitride treated from the factory? From what he told me nitride treating only penetrates .020" into the material so turning a journal further than that would require re treating. The nitride treating is supposed to harden the crank journals and protect against wear from what I understand.

Another concern I have is how my 30/30 cast crank compares to your 40/40 forged crank.

Lastly my boss brought up that since the oiling holes are drilled at an angle that removing material causes the oiling holes in the journal to move offset of the center. I am guessing this is not a major issue for our engines if you are producing 400+ hp without bearing problems but its something to think about.

Any thoughts?

Thanks again,
Maurice

[mopar2ya]

Nitriding a crank can be done to go deeper than .020, If your concerned with it, you can have it nitrided again. But I havent had any trouble yet. WHen you shop does the crank have them chamfer the oil holes in the crank and you'll be fine.

[igotaneed4speed]

a decent shop should be able to re-weld th emass abck on the journals and then machine them to stock spec and re nitrate the surface...... price i dunno how much but the though that counts....



derrick

[mpbiv]

Thanks Derrick

I don't think I would bother having that much work done to a 30/30 crank just to make it stock. If for some reason I wanted to decrease stroke or switch to a rod from some other type of engine that would make sense, but in this case finding a good stock crank should be cheaper.