I think it's machine time

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Feb 5, 2022 | 03:42 PM

#11

Mountainkowboy

Thread Starter

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Joined: Jan 2006

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From: Anywhere we stop

Quote:

Originally Posted by 98hotrodfatboy

What do your pistons measure 1 " from the bottom oil ring on the skirts and are they cast or forged?

I believe it was 3.587. I can't work on her anyhow, the "community" site inspections are next week, so my shed is stuffed full of items that are none of their business. One of the MANY reasons we bought in Idaho..

Quote:

Originally Posted by carlgrover

How close is your repeatability with calipers? Do you get closer than 1/2 a thousandth measurement to measurement?

carl

Hence why I measured them so many times.

Quote:

Originally Posted by Dehammer

I am a machinist. ID measurement with calipers is not applicable for the clearances you are trying to realize. Even a premium quality Mitutoyo caliper has limits. Telescoping bore gauges are problematic as well, even so they should be measured by a micrometer after a gauge block qualification. I do not work with cylinders but I would guess without a torque plate you would get irrelevant readings anyway.

A shop that specializes in doing this work should have the proper bore measuring tool and/or CMM to get you set up right.

Seeing how it had piston slap on cold startups, smoked, and with the scaring that's showing on the piston skits, it tells me that the piston to bore clearances were most likely far out of spec to start with. I was just curious as to how far out that they might be. I will order an overside piston kit and take the lot to a machine shop and have the barrels machined to match the new pistons.

Last edited by Mountainkowboy; Feb 5, 2022 at 03:47 PM.

Feb 5, 2022 | 07:08 PM

#12

Dehammer

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From: Arizona

Quote:

Originally Posted by Mountainkowboy

Exactly what I would do.

Feb 6, 2022 | 07:35 AM

#13

98hotrodfatboy

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Joined: Mar 2010

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From: Poolville

Quote:

Originally Posted by Mountainkowboy

I believe it was 3.587. I can't work on her anyhow, the "community" site inspections are next week, so my shed is stuffed full of items that are none of their business. One of the MANY reasons we bought in Idaho

Sounds like you measured the top of the piston.. A 3 5/8" Forged piston should measure 3.620" at the skirt allowing for .0025- .004" fit with .004" being on the loose side..