To hone, or not to hone, on re-ring?

[freebeard]

Originally Posted by cajunfj40

"I didn't touch the bores, and it did OK/blew up!"

Flathead Ford when I was in college. There was a ridge at the tops of the cylinders. When I started it up it broke the top rings.

[cajunfj40]

oil_pan_4 wrote:

To bore and hone cylinders is usually only 20 to 25 dollars per bore.
Then how ever much pistons are.
When I get an engine I just assume it's going to get bored and have over sized pistons.

Hello oil_pan_4,

Huh. That's not a lot of money, about $150 for my V6. Does that include cleaning? What level of quality does that buy, from your experience, and from about what timeframe (was this the 80's/90's or more recently)? Do you get a "plateau" hone, for example, with the slightly rough (for break-in) but flat (to limit wear depth) tops with the ~45 degree crosshatch going deeper beneath it for oil-holding? A few of the links in my first post went into detail about the process.

Even if it is that inexpensive, adding all the new parts I'd want to "because I'm already in it this far and getting burned by a bad XYZ would suck" and new heads gets really close to just shelling out for a long block. If this was a truck I definitely wanted to drive for 5-10 years, it might be worth it. As it is, this is my "get back into it and learn" truck, essentially considered to be somewhat disposable. So I need to figure out if this is an engine I want to take apart and re-assemble more thoroughly or not.

I need to call around and find out how much it costs to clean and leak-check cylinder heads. If I'm just slapping it back together with new gaskets, no sense in spending $500 on new heads. I just have to not overheat it...

Anyways, anyone else have any luck in tracking down those SAE papers mentioned in the original article I linked? Hmm. I need to see if the library has them on their online service, which means I have to figure out what my library log-in number is, since IIRC it's different from my library card number.

[Grant-53]

From 1977 to 1987 I was outside salesman for an auto parts jobber with a machine shop. We sold parts for all types of engines. At that time an engine overhaul usually consisted of a valve job, and replacing rings and bearings. Perfect Circle sold iron or chrome piston rings. Ring wear is often measured by the gap between the ends of the ring. The bore should be clean and round top to bottom. Since the condition of an engine will vary based on use it use, is important to take measurements. I recommend getting a good shop manual for the vehicle. I tend to use Haynes manuals whenever I buy a vehicle. The manual will tell you the acceptable tolerances and step you through the procedures. Keep track of mating parts.

[tscheerer]

You will have to disassemble the engine to determine what needs done. Find a machine shop that is recommended by people you know and trust, then have them look at it. Most likely need a complete rebuild of engine, short block and heads, at 160k. Otherwise it's a crap shoot on whether the cheap rebuild will run or blow up.

[stockMKIVTDI]

From a machinists point of view.

Realistically you may or may not have to hone the cylinders.

First let me get this out of the way if there is any abnormal wearing like scoring or gouges or anything that looks like friction welded material in the bore honing is useless without a re sleeve.

Now let’s ask some questions.
Are you using the same piston/rods and the correct factory sized bearrings? If yes and just changing rings you only need to use som 600 sand paper and some brake clean to remove the carbon at the top of the bore.

If you are using new or aftermarket pistons rods or bearrings you might consider a mild hone but even then you likely won’t need it.

Now if this was a race car then I would say go for it but otherwise save your money.

[MN Driver]

I thought the rehone was to add friction to allow the rings to seat, but I don't know much about engines. I used to have a 1995 Geo Prizm(Toyota Corolla rebadge) with a Toyota 7AFE engine (1.8l) that burned about 1/2 quart every 1000 miles when I got it with 140k miles. At 200k miles I was on a cross country trip from Minnesota to San Francisco, CA and I was putting in 1/2 quart of oil every gas tank and it burned more oil when things were hot and at interstate speeds. I thought of dropping the oil pan and putting new rings on the pistons as a sort of hobo-rebuild because the rest of the engine was in great shape apart from what was likely worn rings. The reason I didn't was that I didn't want to hone from the bottom and not be able to get everything cleaned out. ..long story short, I didn't do it and around 230k miles, the blowby gasses was more than the PCV system could breathe and I had pushed out a camshaft seal on an out-of-state trip. I took care of the seal and it happened again in about 10k miles. Nearly 1/4 million miles, I sold the car for cheap to someone who needed a cheap car. Would a easy/hobo rering job from the bottom without a hone possibly have kept that engine in service?

[Galane]

How my father did many engines over his life was to first use a ridge reamer at the tops of the cylinders, if there was a ridge that needed to be cut away. Can't get the pistons out if there's a ridge bad enough to catch the top ring.

Then after completely stripping the block he'd use a 3 stone hone with a 1/2" drill, using diesel fuel for lube. Have to keep it moving in and out while spinning it, going just past the top and bottom ends of the cylinders. Hone until the surface is fully scuffed. You're only removing at most a thousandth of an inch while leaving behind a surface that will wear in the edges of the rings for a tight sealing fit.

If you remove the pistons and put them back with the old rings, you won't get the rings back in precisely the same rotations and may end up with leakage past the oil rings and uneven compression.

When you install new rings you have to stagger the end gaps. Put them every 120 or 90 degrees or whatever works to make the longest path from gap to gap.

Some newer vehicles have some crazy durable metal in their engine blocks. I put rebuilt heads on a 2004 Dodge Dakota V8 and at 140,000 miles the factory crosshatch honing marks were still visible in the cylinders. In a GM or Ford smallblock V8 with that kind of miles the bores would be worn smooth with fine vertical wear lines all around.

When you rebuild an engine with new rings, crank, rod and cam bearings, it will take a while to break in. No high RPM operation for a while! Let it idle for a couple of hours and monitor the coolant temp. If it starts to heat up, shut it off and let it cool down, then run it again.

Then take the vehicle for a leisurely drive, keep it at 55MPH or slower. Gently does it for the first 500 miles and you'll not have problems. Always used a non-detergent oil for break in then drained and replaced with detergent Valvoline oil and a new filter.

Never failed for the hundreds of engines dad rebuilt for his vehicles and other people, as long as they didn't hit the dragstrip or racing on back roads before the engine was properly broke in.

Put a fresh engine together then treat it like you're racing (or you actually do go racing) and you're likely to have something go bad.

'Course for the high level drag racing where they pull everything out of the engine between runs it doesn't matter because with superchargers and nitromethane they come close to melting the pistons. They shove so much air and fuel through that blowby doesn't really matter, and if a bearing spins the dragster will be through the trap before the engine comes apart (usually). If the teams were allowed to just swap the whole engine from a ready supply of ones that have been carefully run in, there'd be very few that blow up.

[cajunfj40]

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.

[Galane]

I'd pull the heads and inspect them and the bores before deciding to by rings etc. Where squirting oil in the cylinders makes no changes to compression, it's likely the rings are good.

Camshaft bearings in a pushrod engine can last a long time, when the engine is taken care of. If you can drop the pan with the engine in, it would be a good thing to inspect the crank and rod bearings. Any journal grooving you can catch a fingernail in, out with the engine so the crank can be ground or replaced.

If the wear is minimal a crank can be polished, as long as that would keep it over minimum diameter for stock. If not, grind it 10-thou. 'Course with labor costs these days it may be cheaper to buy a new crank.

The last engine dad and I did, it was way cheaper to buy a new cast steel Eagle crank for the 91 Chevy 350 than to have the original ground. Also upgraded from dish to flat top pistons and King racing bearings. King bearings have a much thicker Babbitt layer than other brands.