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Crankshaft confusion


TylerB46

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Hey guys, I recently just got my 230 back from the machine shop, and they turned my crankshaft. Mains are now .030 and connecting rods are .020. The rod journals on the crank are 2.062, mains are 2.499. I just found out that bearing clearances on these are supposed to be .001- .0015. Does my crank journals seem too big to achieve that?

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4 minutes ago, Plymouthy Adams said:

you are quoting stock dimension, not undercut values....was the crank actually turned and undercut the .030 and the .020 as you state...…..?    I suggest you get you micrometer out and recheck these values...….

I don’t have a micrometer, but I did check with a caliper and the rods were roughly 2.030 and the mains were 2.479. It’s not the same crank I sent the engine with, it had a crack, but my old one was also .020 rods and .030 mains so I measured it too and it’s rods were 2.034 and mains were 2.465.

Edited by TylerB46
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how accurate is you caliper......you are about .002 more than .030 on the rods....the mains look to be within .001 for a .020 undercut value...did you do this measurement every 60 degrees and do the average....if you can borrow another mic of some sort to compare with.....if all else...return to the shop for them to demonstrate the actual values.  In the end, assembly with plasti-gauge is your final moment of truth...

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9 minutes ago, Plymouthy Adams said:

how accurate is you caliper......you are about .002 more than .030 on the rods....the mains look to be within .001 for a .020 undercut value...did you do this measurement every 60 degrees and do the average....if you can borrow another mic of some sort to compare with.....if all else...return to the shop for them to demonstrate the actual values.  In the end, assembly with plasti-gauge is your final moment of truth...

The rods are .020 and the mains are .030. I’m sure all that’s correct, I think I’m just confused on the bearing clearances thing, but I’ll try with the plasti-gauge and make sure of things.

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never leave a bearing fit to guess....always check using the plasti-gauge....some of the cheapest insurance you will invest into...you got this, regardless of the undercut, the matching thicker bearing shells are supposed to put you within factory specs.....and if you get that..you be golden for fit..

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5 minutes ago, Plymouthy Adams said:

never leave a bearing fit to guess....always check using the plasti-gauge....some of the cheapest insurance you will invest into...you got this, regardless of the undercut, the matching thicker bearing shells are supposed to put you within factory specs.....and if you get that..you be golden for fit..

Thank you for your help, I’ll check everything 

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Definitely recheck the dimensions.  Your OP indicated 30 mains and 20 rods and your caliper readings indicated 20 mains and 30 rods for the crank.  Most times your crank grinder will supply the bearings but double check they (or you), didn't  transpose numbers and get you the wrong ones.  Bearing shells usually have the thousandths stamped on the back side.

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27 minutes ago, Dave72dt said:

Definitely recheck the dimensions.  Your OP indicated 30 mains and 20 rods and your caliper readings indicated 20 mains and 30 rods for the crank.  Most times your crank grinder will supply the bearings but double check they (or you), didn't  transpose numbers and get you the wrong ones.  Bearing shells usually have the thousandths stamped on the back side.

I asked them what they were and they said rods .020 and mains .030, and that’s what it says on the tag they game me, but someone wrote rods .030 and mains .030, so idk what they are really 

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2 hours ago, TylerB46 said:

I asked them what they were and they said rods .020 and mains .030, and that’s what it says on the tag they game me, but someone wrote rods .030 and mains .030, so idk what they are really 

again, if you are in doubt, return to the shop that did the work and show them the data is expressed two different ways coming from them to you......or trust your own measurements, bounce against the stock, order your shell and install with use of plasti-gage...if you come up short on the gauge, your shop is going to owe you some work or one heck of an excuse for inability to meet specs.....expect the excuse...dance if you get the straight skinny

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when building an engine -- the block crank bearings rods should make the journey together and the master shop person should do the math and measuring for u Charlie Stephenson

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Always re check engine rebuild dimensions...

Rod bore/crank pin diameter 

Main bores, main journals

Crank end play

Piston diameter

Piston bore diameter/taper

Measure it all!

Be safe...double check your and his work!

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