Good News - No Cracks

[HillBilly2]

I got a call yesterday from the machine shop, the 80's 6.2 block (unknown mileage but the donor was junk) I sent them does not have any cracks. The bores are worn 2-3 thousandths, with about 1 thousandth taper. He said that if he polished the crank it would be around a thousandth undersize.

I'm thinking about just honing it and using my standard pistons. I know there were A, B, & C sizes in the originals. How much difference are there in these? I do have access to some more used OE pistons. Should I try to get a complete set of C's together for this engine before they balance everything?

It will be getting a Banks Sidewinder eventually. Thats mostly to just keep it locked up when it hits a hill, do not expect any heavy towing ever. Will also be getting timing gears. Now, how about a girdle? Do they really help? Necessary, or just hope it helps? Does it require machining?

Standard bearings should be OK, I'd rather it be a little loose anyway. Now if my head guy comes back with a good report I'll be good to go.

Thanks!

[DmaxMaverick]

If you are getting pistons anyway, get them oversized and have the block bored to the pistons. Swapping pistons into a worn bore during an overhaul isn't ideal. OK for urgency situations, but not for overhaul. You're already in there, and a bore job isn't that much more compared to the alternative. This is especially important if you are installing a turbo. If you are using used pistons, size them to the bore, and ignore the letter designations. Measuring is free. Unless you have bore and/or piston damage, do a light hone and use the same pistons (new rings) in the same holes, if replacement isn't an option.

I don't understand how they can say your crank will be under by a thousandth after a polish. A thousandth is a lot. A little loose is fine, but that's a lot loose. A couple ten-thousandths could be acceptable. A "polish" shouldn't be sizing the crank. A full thousandth is a grind, not a polish.

The jury (and opinions) is still out on the girdle. It certainly won't hurt.

Good choice on the timing gears. Also consider the condition of the balancer. Or better yet, replace with a Fluid Damper.

[HillBilly2]

Thanks, I guess I wrote it down wrong when he called, probably a ten thousandth, at any rate he said the crank would be fine.

With only 2-3 thousandths wear in the bores, is it worth it to bore? Come to think of it though, if it went over 100k on 2-3, then a clean bore should set me up for a lot of miles. I understand Mahle are the best pistons, where is the best source? How much clearance do I need? Just out of curiosity how much size difference was there in the different coded sized pistons?

I'm going to go ahead with the girdle, anything available except DSG or are they all the same? I've got the Fluidamper too, with a balance job I hope it will last forever :)

[john8662]

For the bore size you'd want to see what your overall clearance really is.

If you have .002" - .003" additional wear over book STD size on the bore, you have to take into account that the piston skirts wear too.

Measure the bore size, then measure the piston skirts at the specified location and calculate the difference.

.004" - .0045" is considered the correct clearance for a 6.2 & 6.5TD engine.

The .0045 is for the back two holes 7 & 8. (1/2 tho).

Girdle, this is a must-do add-in at rebuild IMHO. DSG is the only one that currently offers a Stud & Girdle retail product, the Studs are equally as important as the Girdle.