Engine: Cylinder block numbers question

[ChampCouple]

Each of my cylinder bores has a number stamped by it. 3, 35 or 4. What are these numbers?



The one the right is a 4.
Thanks,
Mike

[PackardV8]

One explanation I've heard is machining wasn't nearly as accurate then, so after final honing, each cylinder bore diameter was ascertained and stamped with a code. Then, pistons were measured and put into correspondingly marked bins. The engine assembler would read the code on the cylinder and select a matching piston. The idea was this would insure six slightly different cylinders all ended up with pistons which fitted with the proper clearance.

Anyone have another explanation?

jack vines

[Dwain G.]

That's fully explained in every shop manual. As Jack says it's to allow selective piston fit during original assembly at the factory. After 5,000 miles or so those numbers no longer have any meaning at all.

[ChampCouple]

One explanation I've heard is machining wasn't nearly as accurate then, so after final honing, each cylinder bore diameter was ascertained and stamped with a code.

Thanks for the information.

[ChampCouple]

That's fully explained in every shop manual. As Jack says it's to allow selective piston fit during original assembly at the factory. After 5,000 miles or so those numbers no longer have any meaning at all.

Thanks. My other Studebaker block does not have those numbers stamped in the block. Maybe a later engine. Interesting though, thanks again.

[jackb]

I was told that around the late 90's - early 2000's , GM engines (350 +) could developed "piston slap" due to worn engine block molds ??? A further conversation led to the "select fit" piston discussion and how technology had surpassed this procedure... Anyone care to discuss more (Not facts, just hearsay)....