How much can you turn a crank?

[mkmskm]

How much can you take off a crankshaft? The one I pulled out of this old motor is about 0.020" under on the bearing and journal surfaces. The journals have surface rust and the bearing portion is still shiny but has some light scratching so I'm guessing it will need another 0.030" taken at least.

[BRENT in 10-uh-C]

I am hearing of .040 under off the rod & main journal pins. Makes for a "spindely" crank but as long as everything is balanced again, and the engine is not pushed into severe harmonics, it will probably be OK.

[Merc Cruzer]

Your biggest problem is where are you going to get bearings that size? You might want to locate the bearing fist in the size your are thinking about before you cut it….not saying to buy them just locate them.

[mkmskm]

The journal's aren't as bad, the are about 1.48x but with the surface rust I'll bet they will have to be taken down another 0.010 but the mains are 1.61x. I wasn't going to put inserts in.

[Kurt in NJ]

Inserts are available to .040, with Babbitt it can be any size because it is machined to match the crank.
Babbitt rods are mostly done in normal undersizes (010, 020,030), but could be made any size.

A cranks were hardened, not as hard at .040 as they are at std size --but not many cranks of the era were hardened at all.

[mkmskm]

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OK, I'll swing it by the local shop and see what they think it will be size wise if they turned it and then decide if it can be used.

[John S]

Originally Posted by Kurt in NJ

Inserts are available to .040, with Babbitt it can be any size because it is machined to match the crank.
Babbitt rods are mostly done in normal undersizes (010, 020,030), but could be made any size.

A cranks were hardened, not as hard at .040 as they are at std size --but not many cranks of the era were hardened at all.

That's a good point about being hardened. I always thought that the hardening process didn't extend below about .008-.010? That's what I understood about the SBC steel cranks we used to use, at least. Did Ford use a different method to go deeper?

[Tom Wesenberg]

Shops can also POLISH a crank, which removes almost no metal. If you have just light surface rust, I'd go that route. If it's grooved or out of round, then it will need to be turned.

[James Rogers]

I did an inserted motor last spring at the customers request at .060 on the rods and mains. These were AER inserts. No warranty.

[Jim Boehmke]

Stock Model A Crankshaft, Perfectly ground to my rigid specs. Indexing is perfect. Mains -30, rods -20, not bent, not cracked. $371 invested, Price: $371, FREE SHIPPING! Guarantee satisfaction.

[mkmskm]

Jim - I sent a message to your inbox on this.

[Jim Boehmke]

don't know about this In Box.
You can call me in Calif. 925-447-6670 or
Cell 925-918-1523
Jim