|
|
Posted by hemimech [71.10.56.36] on Wednesday, January 06, 2010 at 23:35:41 :
In Reply to: Thinking about ring jobs posted by David Sherman [24.32.202.83] on Wednesday, January 06, 2010 at 14:03:21 :
The in vehicle honing & re-ring rebuild is a quick & dirty way to IMPROVE, not rebuild an engine. The problem with a quick hone job is that it doesn’t correct any of the taper nor more importantly the bore distortion. If one takes the time to measure the bores on a well worn engine with a dial bore gage at several different levels and multiple orientations you will reveal a pattern. The obvious wear is at the top of the bore where the rings twist as they change direction at the end of piston travel. The not so obvious problem lies further down the bore in the form of distortion. The unsupported cylinder walls deform over the years due high heat loads and typical thermal cycling. Most often the cylinder becomes egg shaped as the bore draws near it’s neighboring cylinder. The heat is greater between bores than it is on the sides. So if you ignore the distortion and simply hone the bore then you will get a beautifully polished egg. Hones are spring loaded therefore unable turn an oval into a circle. At this point you are now loading a cylinder with rings that are perfectly round and expecting then to seal on a far from a perfect circle. The fact is you will be loosing some compression in the areas with distortion. When your only starting with 7-7.5:1 I think this is something to be concerned about. Yes the rings will somewhat wear into the poorly shaped cylinder…but never truly reaching it’s full potential. With modern Chrysler engines for rebuild we have a taper limit of .0005” and distortion of .0003” So obviously my jaw almost hit the floor when I hear Chris say a taper limit of .007”. Obviously the specs have been tightened up over the years. But the fact remains the only way to truly restore a cylinder to it’s original performance is to re-bore so it’s once again straight and round. Past my bed time talk to you all later…
Follow Ups: