Hello
As soon as I can I will put the measurements of the cylinders.
True, the air filter has caused the engine to deteriorate.
The small filter was detached and I think it worked for so long.
In practice it was unsoldered from the rear flange. Inside the cylinder head on the intake side, I found tons of deposits, dust and pieces of shit everywhere. This made the cylinders look like mirrors and worn out the rings. The engine apparently has done 2000 hours since it was rebuilt. Poor maintenance of the air filter made the engine almost like it had 15000 hours.
Thankfully, the connecting rods, pistons, bearings, cylinder head and more are intact.

The proper cross hatch honing of the cylinder is important.
To get proper ring sealing and life requires the right amount of oil at the right place at the right time.
Oil is the final sealing element ( sort of the gasket for rings) to have oil rings function correctly and obtain maximum life. It is the cross hatching that controls this sealing. Glazed cylinder walls will not allow the oil  rings to properly seal. Not quite so critical for the compression rings that's why an oil burner can still have decent compression.

i feel proper bore preparation includes proper cross hatch honing too, i think the favourite is like 60 degrees, however that's measured...

-i always thought the cross hatch helped keep oil on the surface the cylinder bore...and helped the compression rings seal, keeping pressure above the rings and piston
-never thought of how that would affect the oil control rings exactly

Hi uisum,
if you found all that dust in the inlet manifold then the rings will definitely be well worn as well as the piston ring grooves.
Cat place more importance on piston ring side clearance in the piston ring grooves for proper sealing to take place.
Measure your new rings in the piston ring grooves for side clearance and check your Service Manual specifications--check for any wear step in behind the ring travel in the groove if there is a step your new rings will likely twist and/or catch and fail.

I believe the maximum ring side clearance for the 3304 when worn is 0.006" or 0.15mm. The normal spec for new top ring side clearance is 0.0037" +/- 0.0009" or 0.094mm +/- 0.023mm.

Cheers,
Eddie B.

If you look at his video at the 10.50 minute mark, you will see him pointing to the oil rings and the lips are almost completely worn away at the ends of the rings, is that because the dust has been moving down through the gaps in the rings?

Eddie, what has caused that dark stain in the center of that bigend bearing, you will see it at the 10.42 minute mark.
Thanks
Mike

I would also seriously consider pulling those liners now that you are in that far.
Even if the bores are ok its a chance to see what the other side looks like. And easier to hone if you don't replace with new. Either way, wrap the crank up good and proper to try and keep the dirt away.

Hi Mike,
could not find what you were talking about in a video but the last pic from his post #229815, the last picture of the piston/rod assembly shows the outer thin tin or tin-lead flash coating worn off and the dark metal is the actual tin-lead overlay on top of the aluminium bearing material which in turn is on top of the bearing steel back--multi layers of materials to make up the bearing shell.
Scans below explain better than I could.
From Cat publication titled "Engine Bearings and Crankshafts" form No SEBD0531
 It is some 1/2" thick with failure explanations on both bearings and crankshafts it also has useful colour Use Again and Do Not Use Again photos.
Cheers,
Eddie B.

Thanks Eddie, for that interesting info on the bearings, your photo of the conrods is what I was asking about, the dark mark on the lower shell of the first conrod.
All the best
Mike

since the engine has been dusted i would fit new liners new bearings possibly new pistons reco the head, whilst the liners are out flush the water jacket thoroughly. then put it all back together knowing its right. you can get aftermarket parts which are often cheaper. don't do a half job it will only fail again probably destroy some thing and cost even more money.

yes no part has broken but that doesn't mean its not worn out the idea is to fix em before things break.

a 150 dollar part put dad on the side of the road for 3 hrs just 15 minutes out of town and cost$90 in wages for dad let alone the 100 bucks a hr for the mechanic to come out and fix it
the part was the filter dryer cartridge for the air compressor dad had told the boss it needed attention for a couple of weeks, the filter plugged the alarm went off and dad was just able to get to where he could stop safely mind you he was still on the fog line before the brakes came on they are held off with air. what would have been a 20 or 30 min $200 job in the workshop became a over $500 fix on the side of the road.

moral of the story fix it properly when its cheaper to do so.