I'm putting together a OT engine, but the question remains the same . Why do they tell you to position the ring gaps at certain point? Once the engine starts the rings will rotate. I'm sure they don't all rotate in sync , so what's the point ? Been wondering about this. Thanks.
So you don't start out with bad all lined up gaps. Yes they run n rotate,but how much depens on hone job,that no ring designer can know,so best guess is start as sheet said.
If the rings all line up you will get blowby. Best to start them out staggered evenly around the piston, give your engine a chance.
In theory with a good hone job, they will all probably rotate about the same. If one rests over the piston pin, it probably won't be there for long.
The rings don't move as much as you might think, especially in a lower rpm engine. I've taken 7500rpm race engines apart after a season, the rings were VERY close to where they were when I put it together..! And that small distance...I could have moved them with the ring compressor during installation, or moved them taking the pistons out. Mike
On my drag race engines I don't see all that much rotation. Granted they don't go many miles between teardowns. Leakage is loss of HP. Pete
I know that 2 stroke engines have a pin in the ring groove to locate the ring gap to keep the ring end from catching in the ports. Makes me wonder about the need or desirability for the rings to be rotating anyway.
I was inside my old racer after 400+ rounds of competition. The rings were where I left them. I ran the Total Seals also, only 2% leak on 2 out of 8 cylinders, the rest were between 1 and 2%. The worst of the 8 had a crack in the #6 cylinder wall which was a common problem with those blocks on anything over over .060.
Stock Hudson pistons have a pin in them that fits the notch in the rings to keep them from rotating. I think Rolls Royce did that too. I doubt there was any advantage to it but it was one of many "fine Hudson features" that made them rather expensive cars.