Bore or just hone John Deere D block.

mrkwpatton · Sep 22, 2011

Guys my machinist called today and said there is 20 thousandths between the cylinder and piston skirts and it should be 7 thousandths. He did say for what I'm doing with the tractor it should be fine to just hone the cylinders and install new rings. Just wanted to see what the masses think because new oversize pistons are $625 plus cost to bore.

petetx · Sep 22, 2011

he didn't mention knurling thr skirts

NCWayne · Sep 22, 2011

Had a customer in the same situation several year ago. We suggested to him that he go ahead and do a PROPER rebuild of the engine and have the block bored oversized. He talked to friends who told him what you've been told, that for what he did with the machine just hone the bore and to go back with standard parts. We did exactly what he asked and made him sign a paper releasing us from any liability should things not work out like he expected. With the engine back together the rings wouldn't seat and the thing smoked like an old steam train.........Longer story short he wound up paying us to have the engine torn apart and rebuilt twice................

Do it right the first time, HAVE IT BORED. The $625 plus you save now could easily come back and haunt you and cost you double that and then some. Like my Grandpa used to say, 'If you don't have the time and/or money to do the job right the first time, where are you gonna find the time/money to do it again the second time?????'

mrkwpatton · Sep 22, 2011

Thanks NCWayne for your input. I was worried about the engine smoking if I just honed the cylinders and just installed new rings. At this point I'm leaning towards new oversize pistons.

mrkwpatton · Sep 22, 2011

What's knurling the skirts?

NCWayne · Sep 22, 2011

Think really hard about what the guy told you concerning the clearances. If there is only supposed to be .007 clearance between the piston and bore but right now there is .020. I know I'm not the greatest at math but to me this means that the cylinder is already .013 oversized for the piston. In other words it's already at a standard .010 over and then some. I can't believe any reputible machinist would even begin to recommend not boring the block to the next standard oversize.

In a worst case scenerio, do or die, your life relied on getting the engine back going, type of situation, I'd at a minimum pressure hone the block to insure the bores were round and then put at least .010 over sized pistons and rings in it. Doing it like this the bore would then be somewhere around .005, or slightly more, too large but even at that it would be alot better than what you've got now at .013 over.

mrkwpatton · Sep 22, 2011

I totally aggree on your math. I think the smallest oversize piston I can get is .045.

Anonymous-0 · Sep 22, 2011

A knurling tool is applied to the piston, as it is held in the chuck of a lathe. The tool knurls, which means raises the surface of about 50 % of the surface of the piston. A knurled surface is like that of a brass handled screwdriver, you know, the ones that have 7 screw drivers, each threading into the next larger screwdriver, and the biggest threading into the handle of a hammer. If I didn't explain it right, Google Knurl, or knurling tool. The idea is to expand out the diameter of a worn out piston, a frequent "cheat" in days of old.

60 acre hillside · Sep 22, 2011

Considering:
Low speed
Low compression
Parade use
He considered the measured wear of the cylinder
Untitled URL Link

lblock · Sep 22, 2011

Can you sleeve it then use same pistons ? just wondering?

teddy52food · Sep 22, 2011

Where do you find .010 oversized pistons?

mrkwpatton · Sep 22, 2011

I guess I could if I can find sleaves.

petetx · Sep 22, 2011

tells ya how old i am don't it

NCWayne · Sep 22, 2011

Not knowing exactly what engine the guy has I was simply making a point that there might be .010 over pistons available and if there were they would be the way to go. Most larger engines, especially diesels are sleevable, have liners, etc, so I was making a guess that this was a 'smaller' engine. As far as where to get them it would depend on what engine it was. I have seen them listed for motorcycles, smaller gas engines, etc, etc. So, for certain engines they are available, but maybe not for this particular one.

Either way I was just making a point that there's no reason to do the job half way if the parts are available to do it right.

RN · Sep 22, 2011

Knurling used to be done fairly often in machine shop of auto parts store I worked at many years back on cab and delivery truck engines, used cars for a couple used car lots. Oversize "Service" rings and a knurl piston with light hone got a lot of +.010/.015 wear engines back on road for another 50,000 miles. Rod and main bearings were often the .002/.004 undersized- like Ford stocks for some engines. Valves often got knurled guides and a lap job. Engines were termed "service/refurbished" instead of "rebuilt". JD light use- can you find the +005/7 chromed service rings anywhere? Or the next oversize ring that can be end machined gapped is what size? RN

NCWayne · Sep 22, 2011

Check out Clevites site. You might be able to find sleeves by tractor/engine mfg, if not then I believe they also have them listed by size, you just have to find the right catalog to download. That said, either way the block has to be bored, but sleeving is going to take more labor than simply boring oversized so your probably not going to be far off, money wise, than you would be by buying oversized parts.
Clevite

CAROGATOR · Sep 22, 2011

going .045 is a lot oversize. some blocks won't stand that much.

WeirdDeere · Sep 23, 2011

We had a D in the same shape (18 thousands of taper), and were debating between an overbore to 45 or boring and sleeving back to standard. Sleeved back to standard to keep the low compression pistons. The price was going to be about the same either way...roughly $1000 bill after all was done, bushings and piston pins as well.

The tractor starts great and runs great too.

If you want it to start and run reliably (especially hand start), I'd really suggest getting a good clean bore, boring or sleeving.

Don't forget to check for piston pin wear, ours were wiped out too.

Brandon

greygoat · Sep 23, 2011

NAPA Auto Parts has sleeves listed by size. But
your machine shop should know that, and have
sources.

Fritz Maurer · Sep 23, 2011

Hey Wayne someone mentioned the danger of boring it out that far. I thought you could take those old Deere blocks out over .100" Heck, you can bore a 351 Cleveland .045 without sweating it. (wouldn't try much more, though). Are two-cylinder blocks that thin?

Mike M · Sep 23, 2011

I'd like to know actual bore wear over stock size at the top of ring travel. Also skirt dia. verses spec. for a new piston.

If the bore isn't too far gone and the skirts are worn down knurling the skirts may work out.

Bore or just hone John Deere D block.

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