08-24-11, 08:53 PM
I have a brand new set of rings from perfect circle but I am confused on how to properly space them out on the piston. I have three different manuals (ondemand5.com, GM manual, alldatadiy) and they all have the same picture. 79389
5.Once the rings are installed, set the ring gaps for the oil control, second and top rings in the positions shown:
5.1. Oil control ring expander and second compression ring gaps-position 1.
5.2. Upper oil control ring gap-position 2.
5.3. Top compression ring gap-position 3.
5.4. Lower oil control ring gap-position 4.
Which view are we looking from (left, right, etc...) or does it really matter.
08-25-11, 11:49 AM
In this diagram the front of the engine is to your left. You're looking through the top of a piston in Bank 2, and the wristpin axis runs through the piston center line. Flop the diagram for bank 1.
The actual number of degrees indicated is not terribly critical - close is fine. You'll notice that the top and second compression ring gaps are 180 degrees apart = least gap blowby.
All ring gap orientation is calculated to allow piston rocking in the bore (wrist pin axis) without unduly distorting the rings - BUT, rings tend to walk around the piston in some bore designs, so this is a starting point for assembly. See the post by dkoz.
08-25-11, 01:07 PM
Phil Irving who was the chief engineer of Vincent Motorcycles says that unless there is an expander or the rings are pinned at the gaps the rings will rotate on the piston at up to 60RPM. The chance of ring gaps lining up is miniscule unless there is already a score in the cylinder wall to catch them. If you disassemble an engine and find a cylinder scored and the ring gaps lined up, the score came first.
I ran an aircraft engine overhaul shop for ten years and overhauled hundreds of engines. The only ring gaps I ever saw that hadn't moved around in the cylinder were oil rings with expanders behind them or rings in badly scored cylinders. Most of those were very badly worn and had broken rings that caused the scores.
01-17-13, 09:14 PM
Sorry to wake an old thread but Sub you mentioned that the diagram in 1st post is bank 2. Is that the left bank? 2,4,6,8
01-18-13, 10:31 AM
Use this............... pre-2000 coil/cylinder numbering