#1 Bore honing and piston rings
Posted: Tue Feb 11, 2025 11:44 pm
My '67 4.2L coupe engine has been going through a quart of oil about every 125 miles. It's not burning it, it's not leaking it out - it just disappears. Engine was rebuilt by the PO maybe 20 plus years ago but has no more the 20k miles on it. It has short skirt AE pistons with a chrome plated 2nd ring. Chome rings are notorious for being very difficult to seal properly. The cylinder walls appear to have a glaze with honing marks very visable. The bore measures no wear (040 over) in all dimensions, so I suspect the issue is that it is glazed over. I had an identical issue (excess oil consump.) on my '68 in the 70's that I fixed with a ball hone (180 grit) and cast piston rings, so I'm reasonably sure that's the same problem with my '67.
The manual for the Ser III XJ6 (copyright 85), at page 12-20 describes deglazing procedure as being done with an 80 grit ball hone (by Flex Hone). Needless to say this is very agressive, however the liner is described as made from Brivadium. Research on that describes it as an alloy developed by Bristol, pre war, for use in it's sleeve valve engines. Contemporary comments describe it as difficult to achive good sealing with piston rings, leading to heavy oil consumption, due to it's hardness. This liner was used in the early XK engoines like mine. Perhaps this explains why Jaguar feels the need for such an agressive hone.
The manual does not describe what the stock rings were made of. Piston rings today are available in cast iron, moly, or chrome, but I'm having a real problem finding the cast iron rings. I have a set of moly rings, but what grit to use honing it. It usually calls for fine grit.
Does anybody with experience in honing, rings etc have any comments. In anticipation of getting cast rings I'v used the 80 grit hone but don't know if it will do well with moly rings, and I can't wait till the end of March for a special order of cast rings.
The manual for the Ser III XJ6 (copyright 85), at page 12-20 describes deglazing procedure as being done with an 80 grit ball hone (by Flex Hone). Needless to say this is very agressive, however the liner is described as made from Brivadium. Research on that describes it as an alloy developed by Bristol, pre war, for use in it's sleeve valve engines. Contemporary comments describe it as difficult to achive good sealing with piston rings, leading to heavy oil consumption, due to it's hardness. This liner was used in the early XK engoines like mine. Perhaps this explains why Jaguar feels the need for such an agressive hone.
The manual does not describe what the stock rings were made of. Piston rings today are available in cast iron, moly, or chrome, but I'm having a real problem finding the cast iron rings. I have a set of moly rings, but what grit to use honing it. It usually calls for fine grit.
Does anybody with experience in honing, rings etc have any comments. In anticipation of getting cast rings I'v used the 80 grit hone but don't know if it will do well with moly rings, and I can't wait till the end of March for a special order of cast rings.