P80 engine cylinder bore marking

[abscate]

Never noticed this before. Piston size for each cylinder stamped into block

All size D on Shagg.

[BlackBart]

100,000.......


or five D's I suppose, just in case you ordered the wrong number of pistons.

[abscate]

It looks like the 1 denotes the passenger side and then each piston size is denoted by a letter for each of the 5 cylinders.

In Shaggs case, D D D D D

Piston size info here…you can order them in size C D. E to match original, or oversize pistons if you have bored out your block

[befarrer]

I don't think there would be any bore size differences on a factory built motor, but there would be weight differences. So I would guess the letter indicates weight of the piston. Most OEM engines have a rather large margin of error for piston weights, Volvo must have had tighter specs, and just machine off a slight bit of weight on the crank to match the piston.

[Sveedy]

So now I'm curious. Part of the point of " mass production " is standardization of parts, so why would factory engines have 3 different sizes, or weights, of pistons ? Different engines, sure. But if we're just talking about the B5234......

[befarrer]

So now I'm curious. Part of the point of " mass production " is standardization of parts, so why would factory engines have 3 different sizes, or weights, of pistons ? Different engines, sure. But if we're just talking about the B5234......

https://www.speed-talk.com/forum/viewtopic.php?t=22423
http://www.kangamotorsports.com/blog/piston-balancing

I'm assuming the stock pistons are cast aluminum. Some might be slightly thicker or denser than others, making them heavier if machined the same. Think of a flywheel, or even a car rim, they need weight added or taken off of one side to balance it because the casting is heavier on one side. Volvo probably went to extra lengths to keep the weights the same for less vibration and smoother engine. I bet the rods have letters on them too.

[454cid]

There is a range for good parts during machining. They're not all the same. I've never been involved with grading within that range, but I've heard of it before with engines/cylinders.

[volvolugnut]

It is a common practice of better engine design to sort pistons by size (diameter). Even the best machine practices will produce a small variation in size. By sorting and matching the engine gets a better, more uniform fit of piston in bores. Citroen may have been the first to do this. Honda was doing it by late 1970's.
volvolugnut

[Sveedy]

As usual, eggs of knowledge cracked on this old bald head

[abscate]

From Swedespeed, unverified

Corrected below post by jreed

Measure 12mm from bottom of piston skirt.
C=82.950-82.960
D=82.960-82.970
E= 82.970-82.980


0.01mm translates to 0.0004 inch or 0.4 thou in machine talk, so these are small differences in piston diameter to match variations in engine bore size

They all use the same piston rings as you would have to set piston ring end gap to spec on a rebuild to fit parts