Hello again all,
Grant-53, I have the Haynes, and I've read several pieces on how to measure bore taper using a single ring and measuring the change in gap as it is pushed down the cylinder. Also the way to measure it right with snap gauges or similar. For what conditions did Perfect Circle recommend chrome vs iron? What bore surface finish did they require to honor the warranty? I've found one ring manufacturer, ACL, that did not recommend honing on a re-ring for their plain iron rings, on the theory that you're more likely to destroy the engine with leftover grit from a poor cleaning job than you are to get poor seating on the new rings in an old bore - when re-ringing on a DIY basis.
tscheerer, well, yes. I have to pull the heads anyway to do gaskets, so I'll be able to see most of the bore in each cylinder and be able to check for a ridge, and check for taper in what I can access. Visible damage will mean either scrapping or further dis-assembly of the engine. That 160k mark for needing a rebuild - what era of engines is that based on?
stockMKIVTDI, you mentioned that one "may or may not have to hone". What do you base the decision on? Can it be "eyeballed" with a reasonable degree of success (I see the cross-hatch, should be good to go), or does a particular surface finish need to be measured to? Obvious damage will be obvious, as will excessive taper and the presence of a ridge. My question is mostly aimed at modern-ish engines with fuel injection that don't wash the cylinder walls with gasoline on every cold start, use a good ring pack, all designed to minimize oil consumption and blowby to get better fuel economy and lower emissions.
MN Driver, no idea. If you were pulling the bottom end apart, pulling off the head to get to the rest of the bore isn't much more work. Plus, if you are pulling the pistons out, I'm not sure how you get a ring compressor to fit right for re-insertion from the bottom.
Galane, that's more good information about "how it's always been done", and generally good advice. I'm not disparaging your advice, just, it's basically the same stuff I've already found.
Generally:
I'm not disputing that the tried-and-true method works, and I'm not "trying to get away with it" by not doing something that "should" be done. (Well, maybe a little...
)
I ran across a claim that the properly worn-in surface finish on a cylinder wall is the "correct" one for best ring seal, oil consumption, friction and longevity, plus some more information about methods of honing to approach that surface finish as closely as possible, and have been having a hard time finding more information about how best to refurbish used engines that don't have a ridge worn in the cylinder. Lots of good testing on machined/honed surface finishes of varying types, lots of great characterization of the wearing-in period, all fascinating. The only thing I've found about "not touching the bores" was the GM LS engine oil consumption problem where the rings were installed upside down at the factory, and the warranty repair did *not* authorize machining the cylinders - and would void the warranty if such work was done without evidence of a damaged cylinder wall. Even then, several of the anecdotes I ran across mentioned the owner of such an engine convincing the tech at the dealership to do the honing "on the side" because it "had" to be done or it would never seat. Not exactly a good representative sample size. There were other bits from aero engines and large ship diesel engines about changing out rings without touching the bores as part of certain regularly scheduled services, but again no study data.
The links to a representative sample of what I found are in my original post.
I do wish I had access to good surface finish measurement devices that I could use on a cylinder wall. We have good devices at work, but I can't bring an engine block in and it won't fit in the device anyway. I can't imagine the labor charge for a good bore surface finish inspection by a good shop being much different from the labor charge to bore and hone the cylinders to the next size up.
Anyone else have any luck finding good testing done on the ring sealing efficiency/break in success of various surface finishes - including the "as-is" condition of a used cylinder that measures in spec - when doing a re-ring?
Realistically, if I see OK compression numbers that don't change much with a bit of oil in the spark plug holes, it'll just be new gaskets and not-cracked heads. Pulling the engine the rest of the way apart would take longer and give far more points of entry for damaging grit, grime, and mistakes. I need to draw up a budget to see how long I need to drive it to pay off new heads by avoiding car payments. Also need to weigh the pros and cons of an in-frame refurbish vs. an engine swap if the bores in the current engine are OK. If I swap in the rebuilt front axle with 4.11 gears to run larger tires I'll have the pan exposed, making a pan gasket, timing chain gasket and water pump replacement not nearly as painful. Heads are a bit of a pain in the truck having to work around the A/C and deal with the exhaust, but more or less than a full engine swap where I have to leave the A/C in anyway? The main benefit to "on a stand" is I can turn it upside down to clean the decks, keep gunk out of the innards better that way. Plus access to the core plugs. Oh, and I would be able to say I completed an engine swap, rather than yanking and replacing the same engine.