TheSamba.com :: View topic - To Hone or not to Hone? Or to just buy new?

Sat Jul 14, 2012 9:22 am

Well while I have my engine in 15 million pieces, it has been suggested that I hone the cylinders and replace the rings. This seemed like a fair suggestion and so I looked into it. However with a very light amount of googling, I was bombared by information of how Honing cylinders that have not been bored is not only unnecessary, but quite possibly harmful. Here is one of MANY articles I found:

http://www.snowvalley.20m.com/bikes/dnthone.htm

Now from what I can tell, these aren't some lazy guys saying, "ah, you don't need no stinking honing!" The SAE (service of automotive engineers) has apparently done studies and found that honing an unbored cylinder is detrimental.

Now, I don't know $hit from toothpaste when it comes to honing (which is why I was googling in the first place) but from what I have seen, honing isn't such a fantastic idea. Thoughts?

Sat Jul 14, 2012 9:41 am

interesting.....

Sat Jul 14, 2012 9:55 am

You also need a torque plate to squish the cylinders into their running shape before honing em.
How many miles on the P&C set? If over 75K you should have em bored and new pistons installed if you want to do it right. I know the shadetree guys will just say "run it" but if you want the engine to last 100k without any problems go the extra mile, just like do the Heads right and forget about em on those long camping trips.

Sat Jul 14, 2012 9:59 am

curtis4085 wrote: interesting.....
agreed.

if you want to replace your rings though (as your compression testing indicated you should) they will need a freshly honed surface to bite into & seat.
this would be a great thread for the engine forum.

if it were me: i'd hone 'em out, clean the pistons, slap some new rings on & forget about it.
you're already reusing 30 year old heads--which a light amount of googling would also tell you is not a good idea.

too bad your CHT thread became the straw that broke The Marine's back, because he'd probably have something interesting to say about this.
what does the SAE know about ACVWs, anyway :lol:

i am assuming that the OP will not be doing the honing himself.

Sat Jul 14, 2012 10:17 am

What a load.....sorry. In that link...there are far too many over laminated/superimposed contexts gathered together as to what can happen, what should happen and why certain things worked or didn't work for a myriad of different people.

In other words....someone decided to gather together all of the issues with honing along with opinions and BS...and make a simple yes or no answer.

Honing boils down to this: cylinders that need to seat rings must have three main things. This is about sealing rings...remember that.

1) Concentricty....meaning they must be as round as possible or at least within specs and must have as little taper along the length of the bore as possible and/or at least be within specs

2) They must be the proper diameter for the application and the piston material used.

3) The cylinders must have the proper surface profile Rz (or Ra) and cross hatch angling ....depending on what the material, profile and specification is for the piston ring set and application. These specs are supplied by virtually all piston ring manufacturers....if you bother to look for them.

What are these #'s?
A for instance.....a given ring manufacturer (for a specific profile, ring material and usage) may ask for a honing cross hatch pattern that is approximately 40 degrees to the center line of the bore.

Too steep of an angle in the honing marks like 60 degrees can cause improper ring ring rotation, uneven wear and /or ring flutter and may even cause oiling problems on some ring profiles.

The Rz is a number that is generated by a profilometer tool that draws a sapphire micro tool across the bore and reads the frequency of bounce. The Rz is the average of the highest peak to the lowest valley.

Ra is sometimes used in some systems. It is the arithmetical average of the same profile reading. It is very exacting and is read in microns and most ring manufacturers have a surface profile listing for honing for various ring types if you bother to look. It is an accurate method of measuring surface roughness

Going back to the example...that given ring manufacturer may list as I noted...40 degrees cross hatch and 50 microns Rz.
To add to this, they may require a "plateau" finish. This is usually done by using a medium grit hone first...like a 320-360....to set the peaks and valleys of the hone marks...the sharp high spots and dull low spots....and then use a 400-600 grit hone afterwards to just knock the sharp spikes off of the hone marks to create small flat spots on top (plateaus) so the hone marks will not be overly abrasive during break in.

What all of this means....and what the SAE was alluding to that if the cylinders have wear and do not have the proper Concentricty of bore to be honed to a spec....just honing them may make the condition worse by taking away material. The cylinders may have to be bored or cut first to restore roundness and taper ......before honing them to give them proper surface roughness for ring rotation and ring break-in/sealing

Honing and boring are NOT the same thing. Boring removes large amounts of metal for re sizing with coarse stones. You will not generally be able to make the proper surface profile for optimum ring seating during a re-boring. This is not to say people do not do it...or that it does not work. But it is risky and can be hit or miss.

This is not to say that every little shop has a $1400 Rz meter (I just happen to have one that I use every day for my industry....that I can occasionally borrow 8) . You can do very well simply by using procedure religiously.

An example of this would be to re bore a 90mm type 4 cylinder to 92mm by first using coarse stones with say a five or six stone cutter out to 91.5 to 91.75mm. Then wash it and use three or four stone hone...or a bottle brush hone....with proper cycle speed and rpm with lubricant....with a counted number of strokes (measuring in between sets) to take it out to 92mm. Then take a 600 grit hone......same speed and pressure....and simply knock the peaks off of the hone marks. As it was just relayed to me last year by someone who knows this procedure very well......running the fine hone in reverse can make a huge difference in just knocking the peaks off or upsetting the hone marks.

If you apply the procedures religiously....results will be consistent and most probably very close to what is required by the ring manufacturer ...without owning an Rz meter. Ray

Sat Jul 14, 2012 10:31 am

I would agree that a process professionally done by a person with years of experience and using a very expensive machine is probably a safe thing to do. However, I feel A LOT of people do their own honing. I could see that such a crude method (a $50 hone attached to a dewalt drill) could be more damaging than helping... Again, I don't know much, but I could see where that could be troublesome.

EDIT* There seems to be different types of honing and possibly some misleading terminology. From what I'm gathering, there is stone honing which should be done after a rebore. This will remove layers of the material as it preps the surface. Then there is flex honing, which is actually more surface prep than true honing. Flex honing doesn't actually remove any material but "displaces" it, creating a surface that is prepped for the new rings. Is this correct, or did I read more hogwash on the interweb?

Sat Jul 14, 2012 10:53 am

You need to measure the pistons and cylinders to see "if" you can reuse em and measure the cylinders to see how much wear there is. Cylinders wear alot at the top and not much at the bottom so to install new rings you need to get the cylinder surface straight and true!
If not the rings will rock and move in the piston lands and wear out quickly plus they won't seal (ie oil leaks and blowby).
Too much side clearance and the piston will slap and rock again wearing out rather quickly.

Cheapest way out if the pistons and cylinders can't be reused is to buy AA P&C's or find a set of Mahles.

Sat Jul 14, 2012 11:23 am

you 1st check the piston skirts about 1" up from the bottom for width. Then mic the cylinder. The clearance should not exceed Bentley specs. If the skirts are not collapsed and the ring lands not worn out, which they commonly are from miles of service, you can use a bottle brush hone to crosshatch the cylinders and install new rings. Be sure to wash and check end gaps and side gaps. This is the least costly and most efficient way to reuse your parts on an inexpensive rebuild. I would call it an engine refresh and not a rebuild.

Or because unlike most engines with a fixed block that cannot be easily replaced, the Pistons and Cylinders can be replaced, so do that instead and scrap the parts. Most likely when you look at the old pistons they will have lots of side scuffing on them.

Do not hone them with a standard hone or bore them out because the cylinders are too weak to support the home properly and the cost to do so will exceed new ones. As a machinist I did many motorcycle engines and air cooled cylinders flex as they are honed because they lack the support of a water jacket. It takes a barrel holder and a torque plate to hone them and all day because normal hone pressures distort the cylinders. Just replace them or bottle brush them.

Sat Jul 14, 2012 12:51 pm

i would just buy new one's,but that's just me :)

Sat Jul 14, 2012 1:48 pm

Ok, well I pulled the cylinders off. I have a caliper, but I don't have a cylinder bore gauge. I'm working on borrowing one. I checked the ring lands, only one of them wasn't within specs. Here are some shots of the pistons. The first pic is the "best" piston, in regards to scuffing, the last two are the #1 and #2 pistons, they have the most scuffing.

2012-07-14 15.33.59 (Large) by riponfrosh, on Flickr

2012-07-14 15.34.38 (Large) by riponfrosh, on Flickr

2012-07-14 15.35.21 (Large) by riponfrosh, on Flickr

Are these unacceptable levels of scuffing? As I said, I will try to borrow a bore gauge. The rings were JUST replaced before I purchased the bus, but I will replace them now that I have it all torn apart anyway. I would definitely like to avoid buying new cylinders and pistons as it looks like Mahle pistons go for a bit over $400. But, would they really be worth it? If I bought new pistons and cylinders (and since I'm having the heads rebuilt by adrian) would I have a 100K motor? Or am I still looking at cracking this thing back open in 20k?

Sat Jul 14, 2012 1:52 pm

Those are pushing the ragged edge of terminal IMO.
You don't really need a bore gauge if you have a good micrometer to measure the piston diameter at the bottom, then use feeler gauges between it and the cylinder to determine bore. Not accurate enough for a final answer but it'll let you know if you are close.

Sat Jul 14, 2012 2:07 pm

If you a "bottle brush" style of cylinder hone, you will be able to do a very nice job on any condition cylinder barrel....these are not "rigid" style hones that must have a perfectly round area to do an anywhere near satisfactory job, the bottle brush hone has hundreds of marble sized stones and is very flexible and simple to use.....three or four strokes up and down in each cylinder and you're done....just wet down the hone with WD40....it doesn't remove metal like a rigid hone either....it just scuff the piston ring surface...don't wast your time with excessively worn cylinders...but if they measure to still be within factory specs....this is the way to go...one bottle brush hone does many different sized bore diameters....I bought my hone at NAPA for $100.00 and have used it often...great investment for the toolbox. :D

Sat Jul 14, 2012 2:13 pm

Something like this?

http://www.amazon.com/Research-FLEX-HONE-Cylinder-...brush+hone

Sat Jul 14, 2012 4:05 pm

MidWesty79 wrote: Something like this?

http://www.amazon.com/Research-FLEX-HONE-Cylinder-...brush+hone

yes just be aware that it removes metal fast and you don't want to make more than 3 or 4 passes. You are trying to spin it while moving it so the lines cross at a 45 degree angle. You do not want circular lines. You also want about 1/2 of the bottle brush to come out at each end before you reverse directions or you will wear the center of the cylinder more than the ends. You can rent them too or pay to have it done.

FYI - if ANY of the ring lands are worn out then the piston is worn out. You may start breaking ring or ring lands if you try to put new rings on a piston that is worn out. The ring will cock too much in the groove as the piston reverses directions. And, if one piston is junk it is false economy to replace just one. You'll need a piston and matching cylinder and the balance will probably be way off too. I would replace those with new ones due to the scuffing at the top alone on those.

Sat Jul 14, 2012 4:18 pm

:( You guys are killing me here...

So... a set such as this...

http://www.ebay.com/itm/Volkswagen-Transporter-Van...1438wt_988

It appears to come with new rings, pistons, wrist pins, and cylinders, at least that's what's pictured. Now... These would already be honed and ready to go right? Just bolt those babies in and run, correct?

Sat Jul 14, 2012 4:34 pm

MidWesty79 wrote: :( You guys are killing me here...

So... a set such as this...

http://www.ebay.com/itm/Volkswagen-Transporter-Van...1438wt_988

It appears to come with new rings, pistons, wrist pins, and cylinders, at least that's what's pictured. Now... These would already be honed and ready to go right? Just bolt those babies in and run, correct? After a through cleaning, checking ring gap and adjusting ring stagger. Nothing is bolt on and go.

Sat Jul 14, 2012 4:41 pm

bsairhead wrote: After a through cleaning, checking ring gap and adjusting ring stagger. Nothing is bolt on and go.

Ok, fair enough, But the cylinder should already be honed correct? I can clean, check/adjust ring gap and adjust the stagger without purchasing anything extra, but if I had to hone it, I would have to buy a honer of some sort. My main goal here is to do this RIGHT, but still not end up nickle and diming myself to death. At $322 I'm actually VERY alright with picking up a new set of pistons, cylinders, rings, and wrist pins. I assume the mahle set is decent? On Busdepot.com they say they are German, but are they still actually made in Germany? I didn't think they were...

Sat Jul 14, 2012 4:43 pm

MidWesty79 wrote: bsairhead wrote: After a through cleaning, checking ring gap and adjusting ring stagger. Nothing is bolt on and go.

Ok, fair enough, But the cylinder should already be honed correct? I can clean, check/adjust ring gap and adjust the stagger without purchasing anything extra, but if I had to hone it, I would have to buy a honer of some sort. My main goal here is to do this RIGHT, but still not end up nickle and diming myself to death. At $322 I'm actually VERY alright with picking up a new set of pistons, cylinders, rings, and wrist pins. I assume the mahle set is decent? It says they are German, but are they still actually made in Germany? I didn't think they were... That's the way to go. Pick up a good scale so you can balance them to a nats ass.

Sat Jul 14, 2012 4:53 pm

bsairhead wrote: Pick up a good scale so you can balance them to a nats ass.

Good suggestion. I assume the rod, wrist pin and piston should all be weighed together. And would just dimpling the bottom with a drill bit or the like mess up the actual balance of the piston itself at all? I like where your heads at, but is this the kind of thing that can actually be done at home? Is it as simple as making them all weigh the same? (Without causing ill effects to the structural integrity of the rod/piston of course.)

EDIT* Looks like there are some articles on this. If I dig out my Muir Idiot's guide there is apparently a write up as well...

Sat Jul 14, 2012 4:57 pm

Careful, balancing is easy to F' up, take off too much and you can't go back, I wouldn't recommend lightening pistons to a novice but Bentley does show where to grind the rods. Match the assemblies as close as possible would be the safe path in your case.