Lister SR3 piston rings

[orakal]

Hi, i have used this forum countless times for advice and answers but i need to ask my own question as i dont think its covered, i have inadvertently broken an inch from the bottom ring of the 3 at the top of the piston so need to replace them.
I have emailed a few people and the site dieselgman is associated with but its in the states for prices and availability.

I'm trying to find some in the UK but nearly every set is the .0010 oversize.
I'm assuming mine are standard as they seem to have a strange assembly in 2 places that's comprised of 3 rings the middle one being an up and down patterned one compressed by 2 thinner rings.(best way i can explain).
My point being if i cannot get a standard set will i be able to get away with fitting the larger ring or will it be just too big?

Also i know if the ring does not sit right it may score the bore???.....is there a possibility of real damage, could i get away with it?.

Im happy to replace the rings if i can get hold of them and im kicking myself for breaking one, so if anyone can point me in the right direction id appreciate it.

[selmawp]

Hi, what is the bore size?

[dieselgman]

We can supply replacement rings - both aftermarket and NOS product.

You can generally re-size a .010 oversize ring to properly fit your standard bore... just file the ring ends until you achieve proper gaps in the bore. This assumes you use a straight and true cylinder bore for the fitting.

dieselgman

[orakal]

I dont have the tool to make the measurements im afraid.
Trying to put a pic up to show you.

Thanks dieselgman, i dont suppose you sell from the uk and if not do you have a rough idea how long the shipping takes?

[orakal]

[orakal]

[orakal]

The lower 2 sets of rings comprising of 3 rings each lead me to think that they are original size and not rebored.

I think most after market are just a single ring?.

Im only doing this as it static seized due to water on the pistons from the air intake, god knows how and she wouldnt turn and just this one came out with the head, the others came freely.

It was easy to remove though, very little force was applied just a medium tap with nothing more than my palm on the big end.

So assuming i cant source a std set i just file .0010 until it displays the same gap compressed as the other rings, but it must be from both ends, and im assuming with a standard metal file as im told these rings are harder than the pistons?, thanks for the imput.

[dieselgman]

The rings used in the SR are of fairly soft iron except for the chromed portion of the fire ring. The pistons are of a relatively softer aluminum alloy. We use a gap grinder made special for the purpose that files both ring ends at the same time... you can easily do the same with a good file.

The rings pictured are likely NOT standard Lister offerings, but rather appear to be AE, or maybe Hastings replacements... Others maybe also have the multi-piece oil scrapers as well, but I have never seen them used from OEM. Stock oil scrapers will have one single-piece rigid scraper on bottom, and above the pin one conformable single-piece scraper with expansion spring behind it.

Assuming .010" oversize rings refitted to standard bore... they are just a little longer and you will file each one to achieve book specification on the end-gaps. This is also a commonly used way to tighten up a slightly loose bore, but only viable if the bore remains straight and true. Best to machine hone your cylinder first to eliminate any wear irregularities and allow the new rings a good chance to break-in properly.

Shipping to/from the UK can be quick if you don't mind the cost... air courier $35 to $150 depending on weight - 4 or 5 days. Postal Service small packet $20 to $50 depending on options chosen - 14 to 30 days typical. These are very rough estimate ranges only.

dieselgman