Piston Ring Gap Orientation

Mini Technical Sections Problems, Questions and Technical
1

Hi,

I have 21253 +20 pistons which have 3 piston rings

Just wondering which way should the piston ring gaps be orientated before putting it into the block?

Thanks

2

There are a few options, but I always space them 120 deg apart if I have 3 rings, the idea is that they are NOT lined up. Ensure the oil ring gaps are not lined up either.

3

There’s also a school of thought that the gaps should face the dizzy side of the engine: centrifugal force throws the pistons against the other side of the cylinder.

4

> There’s also a school of thought that the gaps should face the dizzy side of the engine: centrifugal force throws the pistons against the other side of the cylinder.
That is what I was taught too.

5

Or commonly don’t put the gap on the thrust side ( which is the rear of the piston/block ), but space them so no gaps are above each other…

6

Never heard that. It won’t strictly be a centrefugal force though, but I know what you’re saying.

I’m just trying to get the reason for doing it in my head i.e. what part of the stroke would it be an advantage to put the gaps away from the dizzy. I’ll have to think a bit longer while I knock up a chilli for tea.

7

I have always set the gaps to be more-or-less in line with the gudgeon pins with the gaps alternatively one side then the other down the bore, including the oil ring rails if the bottom ring has them. It always seems to work fine.

8

always opposite each other, example, ring1 at 0 degree, ring2 at 180 degree, ring 3 at 0 degree, and so on

9

At risk of getting flamed, I will say that in all honesty it wont really matter as when the engine is running, do you really think that the rings will stay in the same orientation as when they were put in?

Yes, yes, when fitting the rings to the piston, its easy to position then such that the gaps are not directly above one another, but its not as if they have to be perfectly 120 degrees of seperation. They certainly wont stay that way, and there WILL be a point when the engine is running when all the gaps line up

basicaly, if the ring gaps are not below minimum, dont worry about it too much