Piston size - 86.47?

[dj_efk]

Hi all,

My restoration shop is dismantling my engine for inspection, here is a pic of what is stamped into the pistons.

I'd like to freshen this engine up with new rings - Can I assume that my pistons are .5 mm oversize and therefore I should be looking out for a set of rings to suit? If so then I'm confused by the 86.47mm and then the reference to "SP 0.03" underneath (also I'm at a loss as to understand what the bottom marking says / indicates). Interesting that these are they not just marked 86.50mm as other manufacturers would do/

Finally - Any thoughts on what makes of piston rings to seek out or avoid and why? I see there are a wide range of manufacturers out there.

Thanks.

 

[sfdon]

Your bore is 86.5mm
your pistons are 86.47mm
the difference is taken up by your rings
all pistons are made smaller than bores to accommodate thermal expansion
rings are available on ebay, Amazon, Walloth, BMW - everywhere
Goetze is a decent brand

11251256464

Goetze Piston Rings & Liners | Engine Parts (UK) LTD

Goetze manufacture Piston rings, Cylinder Liners & Gaskets for OEM & Aftermarket. We have a vast range of Goetze on our shelves in the UK.

www.enginepartsuk.net

 

[dj_efk]

Smashing answer which clarifies - Thank you!

So I presume my pistons are indeed what some ring manufactures are referring to as +0.5mm oversized then.

 

[HB Chris]

Yes, second oversize.

 

[stphers]

You can always just measure the pistons to be 100%

 

[dj_efk]

Ok so next question, anyone got 6x set of rings for a 1969 2800cs in .5mm oversize form that they don’t need?!