piston markings

Post by **cadetchris** » Tue Dec 29, 2009 4:49 pm

my pistons have a large 3 stamped on the top of them, does this mean that they have been overbored to 3 thousands?

Post by **mike.perry** » Tue Dec 29, 2009 4:56 pm

No. Not sure what the markings are but an oversized piston would be marked +010, +020 etc in 10 thou stages.
If you are rebuilding the engine have the bores checked for wear, do not just replace the old pistons and rings.

Post by **cadetchris** » Tue Dec 29, 2009 5:03 pm

ahh right. good job i didnt order any rings then

Post by **Cam** » Tue Dec 29, 2009 6:33 pm

I THINK it is a quality mark (tolerance). So you match the piston to the appropriate bore. I think the lower the number the closer to 'original' size it is.

Is that right Roy? (where is he!)

Post by **bmcecosse** » Tue Dec 29, 2009 6:49 pm

Yes - it was a 'grade' mark on the pistons. The bores were never quite right! Started off slightly big and as the tool wore down - came down to the 'correct' size. They found it easier to measure up the bores and fit suitable pistons - than to get the bores all right- first-time!

Post by **bmcecosse** » Tue Dec 29, 2009 6:51 pm

Off topic! - Ahh - now that's interesting - on my Computer NONE of the little automations are working - the 'roll' smilei doesn't roll - and as you all know, my little train ran out of steam!
Any of you computer lads know how to fix this - and yes, I promise NOT to bring the train back - till next Christmas anyway!