gonzo350

1FastBrick

iTrader: (16)

Why would they cut it .040??

gonzo350

1FastBrick

iTrader: (16)

IMO, They should get you another crank.

I personally wouldn't go that much on something being used with forced induction.

Is it only on the rods or the mains too?

Is he aware of your plans for this?

gonzo350

01CamaroSSTx

iTrader: (3)

You requested a polish and most likely that was all it needed. Taking too much off the crankshaft only weakens the crankshaft in my opinion but of course it will still work. How long if your really hard on it would be my concern though. I'd want them to replace it and any reputable machine shop would offer to replace it if the customer chooses not to accept the machined part due to their mistake.

KCS

iTrader: (20)

I would have them replace it or I’d walk away and let them eat the cost of machining it.

R6cowboy

iTrader: (3)

I would opt to have them replace the crank if it were me. I wouldn't care if its still "ok" after their mistake.

pantera_efi

iTrader: (1)

Hi Gonzo, I would be MORE worried with the Bearing Clearance.

The reduction in size equals 6 of the hairs on your head in Radius !

The balance cost of ???.??

What bearings will you fit ?

How does the "fillet" look ?

The ONLY problem you will have is if in a future rebuild the small chance of a >050" quality bearing.

TO BE HONEST, the bearing surface speed will be reduced.
The "smaller" main diameter WILL increase Oil Pressure by a reduction in flow area.

The "smaller" Main Crank will make more HP.

Lance

01CamaroSSTx

iTrader: (3)

That crank could have been machined a few times before reaching 040 but basically now it's one and done!

littlefield

Stresses due to torque and bending will increase about 5%.

pantera_efi

iTrader: (1)

Hi Gonzo, I would like you to post a picture of the Main Fillet area.

The LS OEM crankshaft has a "rolled" Fillet AREA that ADDS much strength to the crankshaft.

I have seen cracks in a crankshaft, often in the ROD fillet area.

THUS if a Machine Shop "destroyed" the Fillet area IT DID in fact damage your crankshaft.

Lance

JoeNova

At what point does bearing thickness start to become an issue?

01CamaroSSTx

iTrader: (3)

Good question! I'm wondering if we're missing something here like the crank was damaged and needed to be machined that much in order to clean everything up? If I handed a machine shop my crank knowing that all it needed was a polishing and was told they took material out I'd be pissed. But I would have measured the journals with a micrometer to see if they are within spec. so I would know prior to the machine shop getting it if there was a problem.

cookseyb

Good Question, I thought the steel shell was thicker and the bearing material remained the same..

pantera_efi

iTrader: (1)

Hi Cook, I agree with you, the steel is stronger/thicker.

AGAIN, the increase in thickness is SIX hairs pulled from your head.

That distance (.020") is not a large change in shell thickness.

The Ford 351-W had a 3" Main with Oil Pressure issues due to bearing area.

I often fit a 351-C main 2.75" crankshaft to cure the pressure problem.

My Lola F-5000 had a SBC with "small" journal Main/Rod sizes

Clevite manufactures THICK main bearings for this COMMON conversion !

The OP stated "balanced" crankshaft, OK what was the BW ?

Lance

RockinWs6

One crankshaft manufacturer tested some shafts that were ground down to .010˝, .020˝, .030” or even .040” undersize and found that there was less than a 4% reduction in the fatigue life of the undersize shafts. Most crankshafts are engineered to be about four times stronger than required, based on mathematical stress and load calculations, so a 4% reduction in fatigue life is virtually meaningless. http://www.enginebuildermag.com/2017...030-field-exp/

pantera_efi

iTrader: (1)

Hi WS6, yes a VERY GOOD READ.

The simple fact of a regrind crankshaft BELIEVED to be weak be some AND the same belief that it is FINE to REPLACE my 60-2 (GM58x) TW with the LOW RES 24ex AND the cost of the DELAY BOX ($350.00) is a FINE METHOD ?

The "twist" difference (a higher amount of crankshaft twist) is much greater with the LOW RES 24ex compared to the 58x Target Wheel.

How Sad.

Lance

YellowToy/A

iTrader: (1)

It is not the overall strength of the crank. They are surface hardened, they have taken all the hardness out of where they have ground. I would not take that crank.

pantera_efi

iTrader: (1)

Hi ALL, the GM OEM 6.0 crankshaft is made out of Cast Iron, by nature it is hard.
The 4.00" forged crankshaft, I ones I have made for my use ARE Forged Steel AND Require a Heat Treat to increase surface hardness.

Lance