Red Dot Green Dot?

[PGHMAN]

Gathering parts to rebuild the SPX 657. I purchased two OEM pistons off Ebay from different sellers. Part number for both are 290 887 062 (two over) but one has a green dot and stamped 78.45/2054a and the other has a red dot and stamped 78.44/2054b.
Why the different sizes with the same part number? Should they match or is ok to use? I am planning to have a local machine shop bore the cylinders.

 

[jhjesse]

The difference in diameter is only 1 one hundredth of a millimeter. Basically if you took one of your hairs and split it 4 ways then took one of those fourths and split it you would be getting close to the difference in your piston diameters. Probably not a problem.

0.01mm = 0.0003937 inches

 

[jcleary93]

just bring both into the machine shop and point it out to them so they can machine them accordingly. also are they made by the same company? you want them to be equal in weight.

 

[wfo speedracer]

The dots are for minute mfg tolerances that only Manufacturers worry about, just have your machine shop bore each cylinder to a specific piston and mark which goes where, they should be doing this anyway.

 

[PGHMAN]

Thanks guys.....I was hoping I did not pull a blunder.

 

[jhjesse]

I would just bore the cylinders and not worry about it. Most cylinder boring Machines can't bore to that close tolerance.

 

[PGHMAN]

The dots are for minute mfg tolerances that only Manufacturers worry about, just have your machine shop bore each cylinder to a specific piston and mark which goes where, they should be doing this anyway.

Ha, a 787. I wonder why I bought but it's within budget and I've gathered a slew of parts the past few years to ease the expense.