Piston Pin fit in OEM Pistons

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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jevans
Posts: 13
Joined: 11 years ago
Location: Sooke British Columbia Canada

Piston Pin fit in OEM Pistons

#1

Post by jevans »

One of the cylinders in my sd22 has low compression. Pulled it apart and am doing a refresh of the pistons, rings and liners. The OEM pistons have the steel insert supporting the first ring and was hoping to reuse them. I measured them at 2.756" from the piston crown and they were all within the wear limits. Actually surprising as the machining marks were still visible. One of 4 pistons have a crappy small end bushing in the end of the con rod and so that can be dealt with. But I also noticed that the piston pins move in the piston bosses. If I look a the manual it says there is an interference fit and that you have to heat the piston to 80 degrees Celsius to get the pins in. I can tap the pins out with a hard faced mallet and they have a place where they can move easily within the boss. With 0.0001 thou maximum interference is this usual to see the piston pin loose. If so is it reasonable to reuse them or are they at risk of ? I would measure them but I don't have anything that measures to that accuracy in an inside dimension as it is unlikely that the pin is worn but the piston is deformed. Chinese pistons look like the next course of action, or could you get the pin plated and the piston honed to restore fit. I would like to retain the steel retainer as I was thinking of fitting a turbo, or at least playing with the idea of it. Any knowledge would be much appreciated.
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plenzen
Posts: 890
Joined: 16 years ago
Location: Cochrane Alberta Canada

Re: Piston Pin fit in OEM Pistons

#2

Post by plenzen »

I would mic the pins just to see, but I think your correct that the pistons are starting to wear. You may want to check your rod length too, or put a dial indicator on the deck and see that the pistons are all coming up to where they need to be. I think there is a spec on that somewhere.
No process that I know of for putting sleeves/bushings etc into the bosses. Your likely stuck having to get pistons and pins. They usually come as a set. If it was going back naturally aspirated I might roll the dice on them as they are, but being as how you may add a turbo not sure how long they would last. IMO that is.
Pretty sure there are some other people on here that may chime in.
They continued to use these engines in forklifts for quite a while after the automotive/marine run was done with them. Someone may have a box of 4 on a shelf someplace but it will take some looking for sure. If you were to find some it may be more like a lottery win.
Might want to check Australia as well. There were a few members on here some time ago that were able to get some bits and pieces there. Not sure if any of those members are even still on here, but might be worth a try. Shipping might make it prohibitive however.
Good luck.
P
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN
jevans
Posts: 13
Joined: 11 years ago
Location: Sooke British Columbia Canada

Re: Piston Pin fit in OEM Pistons

#3

Post by jevans »

There are two on ebay right now. NOS ones Std with the steel carrier. If someone has two more I would be interested in hearing from them as well. The part number is 12010-36W10. If I don't find anything in the next couple of days I will go for some 5 ring ones without the steel carrier and cross my fingers.
jevans
Posts: 13
Joined: 11 years ago
Location: Sooke British Columbia Canada

Re: Piston Pin fit in OEM Pistons

#4

Post by jevans »

Why are there oversize pistons and rings available for the sd22 and sd33. Is it an acceptable operation to bore and hone a liner. I talked to my machinist and he pretty much said that it wasn't a thing but he also works mostly on gas stuff. There are some OS pistons out there and so might consider those if it is a thing?
plenzen
Posts: 890
Joined: 16 years ago
Location: Cochrane Alberta Canada

Re: Piston Pin fit in OEM Pistons

#5

Post by plenzen »

You would have to get oversized liners as well. Can't do anything with the ones in there now. I believe they are chrome. Might be able to de-glaze them a bit with a ball hone, but other than that, not much will touch them.
You might be able to get piston and liner kits (in a box, come with pins and back in the day they had rings on them as well) , but not sure you'll get the ones with the steel insert in the top ring land. I bet they are pretty scarce these days but there has to be some someplace. That said I also belevel that Elvis still alive in Arizona cooking burgers.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN
jevans
Posts: 13
Joined: 11 years ago
Location: Sooke British Columbia Canada

Re: Piston Pin fit in OEM Pistons

#6

Post by jevans »

I got a set of pistons from SMS diesel spares in Australia with the Alfin pistons. Alfin being the piston type with the steel support ring. They had them for the sd22 and the sd33t. I ordered the sd33t type pistons. Just for everyone's info if they are looking for some.
plenzen
Posts: 890
Joined: 16 years ago
Location: Cochrane Alberta Canada

Re: Piston Pin fit in OEM Pistons

#7

Post by plenzen »

Did they come with Pins and Rings ?

Good find ☺
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN
jevans
Posts: 13
Joined: 11 years ago
Location: Sooke British Columbia Canada

Re: Piston Pin fit in OEM Pistons

#8

Post by jevans »

They came with pins but not rings . The sd22 pistons were offered with rings and pins. I ordered rings from a company in Dubai. They were the sd33t part number 12033-C8702 ... NPR brand. I haven't received the pistons yet they are still a few days out.
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