Confusion about piston's 3 different OE numbers

[CosmicWanderer]

Hi y'all,

For those who read my introduction post, you already know the catastrophic failure of cylinder #3. Now, I've started to order some parts, and hopefully, after the summer season, I'll start working on the car. Need an overhaul, almost completely - crankshaft & connecting rod bearings, thrust washers (why not? ), pistons w/ pins, piston ring set, valves, valve seal / o rings, timing belt, timing belt tensioner, two idlers of belt, v-belt, vane pump belt, etc.

I've got 3 part numbers for the pistons, and I'm not sure what's the difference between them. The prices differ from each other. I don't know which one fits my ST185L-BLMVZG.

131018838101	3SGTE..ST185 STD,MARK 1
131018838102	3SGTE..ST185 STD,MARK 2
131018838103	3SGTE..ST185 STD,MARK 3
1310388381	3SGTE..ST185 O/S 0.50

What do those really mean? Mark 1,2,3? O/S 0.50? Or maybe I should open it up to see if there are any stamps on the piston(s)? Attached are some shoots of piston no. 3.

Regards.

 

[RedCelicaTRD]

When originally manufactured, the bore was measured and a specific piston fit a specific bore size. Due to machining tolerances from bore to bore, the pistons are slightly different diameters to achieved proper clearance. The oversized is an obviously 0.5mm, but the mark pistons are only about 0.01mm difference.

 

[RedCelicaTRD]

Also, I wouldn’t bother with a factory piston. Aftermarkets are plentiful and stronger. You should have a machine shop check the cylinder for damage and find out how much it will need to be bored for a clean surface. 1.0 mm is the most oversized you should go. Best thing to do is have them bore/hone and then order pistons based on the exact bore dimension. Companies like JE offer this type of custom piston service.

 

[CosmicWanderer]

When originally manufactured, the bore was measured and a specific piston fit a specific bore size. Due to machining tolerances from bore to bore, the pistons are slightly different diameters to achieved proper clearance. The oversized is an obviously 0.5mm, but the mark pistons are only about 0.01mm difference.

Thank you for clarification. Guess I have to remove pistons and measure the bore first.

Also, I wouldn’t bother with a factory piston. Aftermarkets are plentiful and stronger. You should have a machine shop check the cylinder for damage and find out how much it will need to be bored for a clean surface. 1.0 mm is the most oversized you should go. Best thing to do is have them bore/hone and then order pistons based on the exact bore dimension. Companies like JE offer this type of custom piston service.

I went after OE because the prices are around $70 per piece. Any good aftermarket brands providing good price / performance ratio?

 

[grip-addict]

There's a lot of options that people have used over the years. I've never heard someone being unhappy with their aftermarket piston purchase on this car. Wiseco, CP, JE, Diamond all come to mind. If you can find it in the price is reasonable it should be fine.

 

[CosmicWanderer]

There's a lot of options that people have used over the years. I've never heard someone being unhappy with their aftermarket piston purchase on this car. Wiseco, CP, JE, Diamond all come to mind. If you can find it in the price is reasonable it should be fine.

Checked few of those, the avg. price is around $200, almost 3 times higher than OE per piston. To be honest, I want to drive and feel this original stock ST185 before going to forged parts.... and save some money thorough this process.