When to bore .030

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Markstrimaran
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When to bore .030

Postby Markstrimaran » Thu Sep 28, 2017 6:39 pm

6.2 Detroit, with 40k, light rust on cylinder walls.

The last photo was with head just pulled. It cleaned up very well with steel wool. No scoring, cross hatches still noticeable.
Should have taken one last after photo.ImageImageImageImageImageImage

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Tatsadasayago
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Re: When to bore .030

Postby Tatsadasayago » Thu Sep 28, 2017 7:03 pm

Isn't the 6.2 sleeved? It looks like that one spent some time underwater.
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Markstrimaran
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Re: When to bore .030

Postby Markstrimaran » Fri Sep 29, 2017 3:56 pm

I don't think they are sleeved. Cummins are.

Well I would like to bore .010 and intall new pistons with new rings, but don't have a grand to spend.

So still need to get a engine stand, well build one, to get the crank and piston out.
Before I can tell much more.

Thinking a very slight hone, then go .010 rings on stock pistons.

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Tatsadasayago
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Re: When to bore .030

Postby Tatsadasayago » Fri Sep 29, 2017 4:36 pm

The bore looks like it was in great condition before the water intrusion. +.010" rings with a good bar hone job ought to fix it up nicely. Might want to watch the end gaps though...
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SJTD
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Re: When to bore .030

Postby SJTD » Sun Oct 01, 2017 8:33 am

.01" Rings in a standard bore after a few tenths of honing. Is that often "done" on these?

Seems way to tight even with proper end gap. And the support on lands would be less than normal maybe encouraging them to rock?

After some thought I suppose not. I'm guessing the width of the rings are the same.
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Nikkormat
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Re: When to bore .030

Postby Nikkormat » Tue Oct 03, 2017 11:42 pm

Knock on wood before reading, but my first 401 had worse bore rust than that and it cleaned up with scotch brite and a hone job. Still has stock pistons and rings despite 130 ish k miles before I tore into it. It even had a noticeable ridge at the top of the cylinder. And it still has compression 25k miles later. As I said, knock on wood...


Point being, I think you'll be fine.
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eggman918
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Re: When to bore .030

Postby eggman918 » Fri Oct 06, 2017 9:05 am

I was in a similar situation with my 4BT it would have cleaned up with a professional hone BUT it would have been right at the max limit for piston to wall clearance that Cummins says is acceptable. So between the need for proper compression for a diesel and the expected lifespan of the B series Cummins I chose to bite the bullet and went .020" over..............$.02
1967 Wagoneer soon to be TDI powered
1968 F-250 CrewCab Cummins 4BT, ZF-5, NP 203/205,TruTrac's front/rear.

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Markstrimaran
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Re: When to bore .030

Postby Markstrimaran » Fri Oct 06, 2017 10:01 am

Been busy working Saturdays, Thanks for the advice.
No shut downs until Christmas. So only dreaming till then.

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