I’m fixing a base gasket leak and found this scuffing on these pistons.. They are the s&s 4 inch bore pistons that bolt on a 96 inch case . They have about 8.K miles on them and am considering replacing them and the jug . These are really more like scuffs and dragging a finger nail across them , you can’t feel them ..What do y’all think caused these marks and would you re-ring the piston , hone it and run it ?? The cylinder looks great …

 

Didn't know you could use 4 inch bore on 96 cases. I thought the largest you could go was 3 13/16"

 

Drop in 110 I assume he's talking about.

 

So it's an O ring and not a base gasket?

 

. It’s a 110 s&s drop in kit that fits these 96 cases .. And the leak at the base is an o-ring and not a gasket. My apologies if I had said it was a gasket.. But back to my question about this scuffing.. I’m thinking that I should invest in calipers for this size bore and use my bore gauges, and check for any inconsistencies… This build only has about 8k miles on it .. any input would be appreciated.. thanks in advance…

 

Why do the scratches near the wrist pin in the second pic have a curve to them when the piston travels in a straight line? Dirty assembly?

 

OK so you have later twincam cases say 07 to 10-11 and a SnS 110 kit.

Well, I wouldn't use calipers to measure the pistons. Buy a micrometer. You say you have snap gauges?

As far as the pistons go, they may be OK but it looks like the cylinders weren't clean or oiled when installed on the pistons originally. The scratches look more like the lead in edge on the cylinder spigot had a burr on it that scratched the pistons. There may be a small ding or simply some foreign material that put that one scratch, Need to look at the cylinders. I guess you could run a fixed hone through the cylinder real quick to get an idea of the condition of the cylinder spigots. They may be damaged which caused the scratches.

 

I have used pistons in similar condition after measuring to insure they were in spec but they were going into freshly bored cylinders, so no cylinder wall scratches and a know true bore. I would measure everything for fitment and, if necessary, follow Max's suggestion to check/clean up the cylinder walls and if all turns out to be in spec, no spigot damage, put her back together. JMHO

 

.. I have micrometers on the way .. thanks for the advice.. makes good sense

 

torque plate & check the cylinders with a bore gauge.pistons look like they were inatalled dirty or your getting debris from somewhere else (could be the start of rod bearings going south) dosnt look like S&S stuff though,they use a 2mm oil ring and the oil rings look bigger than that.