JJ291

I'm rebuilding my engine. I had a local machine shop clean up the block and pistons and do a light refacing on the valves and seats. After getting it all back, I was taking measurements on my cylinders when I noticed a vertical scratch. The honda manual says that a vertical scratch is ok as long as it does not catch your nail. This just barely catches my nail meaning I can feel it as I pass my nail across but it can't really "stop" my nail.

Am I hosed and do I now have to have the cylinders bored out? I'm not really impressed with the machine shop and think they may have honed the living crap out of the cylinders because I'm just below the service limit.

Any help is appreciated.

RIPSAW

I have put about a dozen engines together in my garage over the years and what you describe is a whole lot less then the ring gap. I sure would not worry about it. I put a old 1960's Ford 6 cylinder back together that had .015 wear and taper. It went 100K after that. A 1969 Firebird at 100K with .005 wear and taper and lots of grooves and it now has 250K on it. A 1985 Civic at 100K (cam shaft broke) Cylinders looked like brand new but re ringed it. Has 300K on it. Many more for friends. All I ever do is break the ridge ring at top. Rough up the cylinders with a hone stone and lap the valves if still even or have them ground at a local shop.

JJ291

Cool - I will go with it. I took some 400 grit sand paper and lightly went over it just finger touch at a 60 degree angle and it is pretty negligible now. I appreciate your insights - feeling better about life!

JJ291

I'm right at the service limit on my cylinders. I think I may have picked the wrong machine shop but I will give him the benefit of the doubt. I have standard pistons and rings. I realize this is more of a philosophical question but what would you do? I hate to bore it out and have to get new pistons, rings, etc. At the same time I hate to have to do this all over again in less than 100K.

RIPSAW

I assume you are referring to the clearance in the cylinder bores and to the wear at the area on the pistons that you measure at. All used stuff. If it falls in the tolerance of the Honda manual, I would not worry about it. Only engine I rebuilt that actually failed to wear that I should have fixed while apart was a 62 Corvair 150HP turbocharged Spider. The valve stem guides were a mess.. probably .02 wear but I was living hand to mouth then. One of the pressed in seat inserts in the head came out. I personally think you will be fine. Just drive it right and keep your gas pedal off the floor. However if you need a pocket rocket..make it new. Ask Ezone on here. Sure he's keeping an eye on us and this forum is darn lucky to have someone like him on here.

ezone

Thanks for the kind words. I don't normally like to jump into threads like this because this isn't something I do much as a tech. Used replacement engines can usually be had cheaper than having me do a rebuild at shop rates.

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I expect if I were to send work to a machine shop---I certainly expect that shop would do professional work, and yours sounds questionable.

I actually have the same problem here, our last remaining local automotive machine shop has gone way downhill (hiring people who definitely have no idea) and I flat refuse to send any more cylinder heads to them. I am willing to send customer heads to the town an hour away just so it's done to my satisfaction. I HATE having to deal with someone elses' crap work and worrying about whether it will survive or not, while having MY NAME on the job.

(Yeah, I think some days I write my name in crayon.)

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Measure cylinder(s) per the book. (Hope they are still perfectly round, if it's been honed you may want to double the number of measurement positions.)
Measure the piston(s) per the book.
Calculate piston skirt-to-wall clearance, for this will be piston slap if clearance is excessive.

Here's the specs for (random) 2002 1.7L copied from the Honda info:
Piston-to-Cylinder Bore Clearance
New: 0.010-0.040 mm (0.0004-0.0016 in.)
Service Limit: 0.05 mm (0.002 in.)
Not much room for error there.
Got metric micrometers?

Do you have micrometers that measure down to 0.0001"?
Not common, and not many mechanics ever need to measure that precisely.
(I do have a 0-1" micrometer of my own that measures that small, but I can't remember the last time I actually needed to use it LOL)





If all clearances are not exactly the same, I might swap piston positions so that clearances are all as even as possible (but that may leave you with rod bearing fitment issues later, if you plan to use that method). If excessive skirt-to-wall clearance is found.....you should know what's next. If you need another stock block, used engines can be had fairly cheap.

Stick the rings in the cylinder one at a time using one inverted piston (again, as per the book), and measure ring end gaps before installation. Compare to spec. If gap is too large, that's gonna be a problem.

I personally wouldn't have touched the bores if at all possible. If the original honing marks were all visible and none had worn off, then the cylinder did not have significant enough wear to worry about. If there was cylinder wall wear significant enough to worry about, the crosshatch marks would have been worn through.
The factory has us stuff new rings in without doing anything at all to the cylinders, regardless of mileage. We have a few updates going on right now for ring issues on newer engines (not any Civics), mileage is not even a factor.





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This is why there are published specifications for nearly all aspects of that work.
It's either within spec or it's not.
If it's not in spec, they should have let you know.
Hmmm....First oversize 2002 EX piston $78 each retail...

Used engine is probably a lot cheaper than pistons plus all that work.
Back when I was getting formal education we were taught to only expect an additional 50% service life from a typical overhaul. This was back in the days of rebuilding engines that used high tension piston rings and they needed routine ridge reaming, if that says anything. Times and engines have changed a lot though, I haven't seen a ridge on anything in decades.

JJ291

Thanks, EZ One...or as I prefer, Saint EZ One (in the world of Honda!).

Pistons all came in at 2.9520 (I think standard is 2.9520-2.9524)
I used a Fowlers bore dial indicator to take my measurements. I set an inside micrometer to 2.9528 which is the low end of the standard range and put the bore dial indicator inside the micrometer and wobbled it back and forth. I set the zero mark on the dial indicator to the point where the needle reversed position.

I then put the bore dial indicator in the piston and checked the x and y at 3 points up and down the cylinder per the manual.

On average cylinders came in about 0.002" short, with one at almost 0.003" short. This would put me at 2.9558 or so. Service limit is 2.9555 if I remember correctly.

I installed the rings using the piston and measure the ring gap. That came in a little bit better but was still just a touch below the service limit.

Can't tell you how much I wish I could go back in time. I was thinking I could just do a light hone but clearly I was wrong.

I had the machine shop do the honing, clean the block and pistons, and reface the valves/guides. I'm pretty concerned about the head now.

I don't mind fining another shop and having them bore out the block and buying new oversize pistons and rings but it's a bummer to pay for someone to screw up your engine. However, it's my own fault in the end - should have just left it alone.

If I was going to make it another 100K I'd probably not worry about it but I just hate to be burning oil in a year.

ezone

*drool*

Are you a machinist by trade? Hot rodder?
That's stuff most people have probably never even seen, let alone have and use.



So they are still within the NEW spec, well above the service limit spec.


*punches calculator*
Skirt clearance then should be at .0038".
Hmmm....Over spec, nearly double the limit. It may not sound like a sewing machine anymore.
Wait...You already said in another thread you thought you had piston knock....

On a purely technical standpoint, strike three- it's out.
On a real world standpoint, will it run?.....Um, yeah. Will it last? I dunno. Will it be quiet? Probably not.

For giggles, look up some other manufacturers' similar bore size engines and see what clearances they find acceptable.

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I've heard of a couple other locals here getting their money back from the machine shop when they screw up. Hard to bring back rare and valuable stuff if it gets screwed up though.



(I looked up your IP on this because I couldn't quickly find your location...and also replied to an old thread LOL) If you wanna drive a little while....Brooks Elliott is a member of a professional forum I participate in, very reputable top notch work on heads.
http://austincylinderhead.com/
Give a call, send your head there, chat a minute.... maybe he knows a good machinist to do your block?

RIPSAW

That's what I figured it would be Ezone..Honda's tolerance are crazy close. Few auto machine shops can hold anything close to factory without big bucks. I worked in the Shipbuilding trade in the machine shop division and engineering producing Nuclear Submarines and Air Craft Carrier for 46 years and though it was bad but necessary tight there.

ezone

This is probably true....but I expect a cylinder head to come back with the correct finish on the head gasket surface after machining. Nearly glass smooth finish for a MLS head gasket is the norm. (15-30 ra)

Some have come back from our local looking like the kids just got a freekin belt sander for Christmas.
But a nuke engine doesn't have piston skirt clearances to worry about LOL

RIPSAW

Year ago when I rebuilt the 85 Civic with the 4 valves with the little precombustion small valve chamber, I got a local shop to redo the valves (valves hit piston when cam shaft broke) I noticed the odd finish on the head. They actually had a huge belt sanding band running across a cast iron table and did it by hand. Trouble was he hit the cam side also. Believe it or not, he did not take enough off to hurt it since the cam shaft fit was great. Interesting part about this was it was one of the first 85's off the line and it had the 84 smaller diameter water pump cavity. Just happened to catch it in my **** habit of checking and turning stuff. The 85 pump call out had a 1/8" bigger impeller and would only turn a 1/4" before locking up..just enough to let it bolt on. Years later on the 3rd or 4th pump, using the vin # at the dealer, he would still give me the wrong pump. Sure that gave a few garages nightmares.

JJ291

Yah - that's pretty much what I thought - only a few options left.

Since the standard bore size for a 0.25" oversize is like 2.9626 and I'm at about 2.9555 (difference of less than 0.01"), think I could just get a honing tool and lightly take it off until right when I'm at the low end of the spec? Or does that much thickness call for having it bored out at a shop?

Thanks.

ezone

Definitely not my area. Ask a machinist. Ask local racers about a good machinist?

A dingleberry hone has no control over keeping it straight. Probably the equivalent of trying to plane a board flat with a sandblaster.

RIPSAW

Any up size for over pistons require it to be bored. The only hone it to produce the finial few .0001 (English system) and then the crosshatch. It would not be round and since the wear is at the top of the cylinder, it would be a real bear to even get it close top to bottom for new oversize pistons. You are better off to leave it as is. It will go 100K as is with new standard size rings. They will seal. It may be a little noisy at start up but quite down in seconds. It will be no louder then when you tore it down.

JJ291

Thanks, fellas. I think you're right - I'm just going to go with it. I commute in Houston and all this city does is beat the living crap out of your car. I'm getting more comfortable pulling my engine so I can always deal with this again down the road if it gets too bad.

Thanks for all the help - sometimes it's good to hear someone with experience say "just relax, it's all gonna be OK."

ezone

^^He's probably right. It already made a little noise, at least you will know why now when you hear it.

Pretend you never measured anything and slap it all together like everyone else LOL

JJ291

Lol. I can always turn up the radio! You got me pegged, it will drive me frigging crazy, no doubt. But I do think it will go for a while and this is my target...long enough for my wife to forget about all the money I just spent doing this so I can do it again!

Til next time!

RIPSAW

Be sure to check the valve grind job. Should hold a few ounces of kerosene poured on top of the valves. I reread and I never did figure why you tore it down or how many miles were on motor? Just how noisy was it? You were not hearing a scratch. Ezone, my friends brother in law owns a foreign car repair shop that is highly regarded in this area. He replaced the motor in my friends Toyota that had coked up and prevented the oil from getting to the pickup. He said he got the used motor from Japan. His spin was some of the big cites in Japan have restrictions on how many miles on a motor are allowed due to emissions and they replace them and sell them as used. Ever heard of this? Is the used motor you are referring to a factory rebuild?

JJ291

Well, it sounded like piston slap. I thought that was a sign of bad rings but didn't realize it was a sign of clearance issues otherwise I probably would have approached this differently.

I will check the valves. He refaced them so who knows how they are now. In retrospect, I wish I had just cleaned them up and lapped them myself.

I'm going to slap it all back together and see how I go and just plan to do it again down the road. Next time I would probably bore it out and get oversize pistons, etc.

Thanks.

RIPSAW

Make sure you have no play in the piston and pin other then side to side.. Also, the ring groove in the pistons should not be much wider then what is called. This is actually how the rings seal and expand out. This is really where the pistons wears out. The piston pin clearance is what goes on Harleys and older 4 cylinder Toyota's. (they have full floating pins with bushings however)

ezone

Many manufacturers have this problem. I just replaced a 5.7 Hemi that spun bearings and cracked the block because of sludge that blocked the oil sump.
I've heard that for a couple decades now, but a member of a professional forum who owns a shop in Japan explained how it works over there...IIRC it's the taxes that make people dump cars so quick. The older a car gets, the more heavily it is taxed. After only a few years it makes economic sense for them to dump an older car in favor of a newer one.

That's how I remember it, anyway.
No, that would be called 'rebuilt', reman', or something along those lines. And I don't think Honda sells reman engines at all, but other companies sure do.

I meant USED. As in junkyard used. $500 all day long used.
www.car-part.com

Consider carbon knock? It sounds and acts very similar to piston slap.
Carbon buildup on top of the pistons can cause a lot of noise if it gets thick enough to contact the cylinder head.



Full floating wrist pins are used exclusively in all marine applications.

(That's a joke, Son.)

sdaidoji

iTrader: (1)

try the XADO engine treatment?

did not destroy my mazda engine. I saw an article on the racecar engineering (reputable mag), so that's why i decided to try on an engine that was getting tired anyway. Good to try if your engine is getting on the way out anyway...

maybe not in winter, since the oil need to heat up for it to dissolve in it.