Rational for piston cylinder deglazing

[steppinthrax]

I understand the difference between cylinder honing (enlarging, correcting) v.s. deglazing (diy mechanic can do).

My question is when you pull a engine apart and see the cylinder walls are shiny (glazed) does that mean the cylinder walls are worn? I've seen people pull engine apart and you can still see the original hone marks on the engine (are those from the deglazing stones)?

So if and when you do deglaze a cylinder wall and put new rings, do these marks eventually wear off returning the cylinder back to a shiny surface?

 

[Ramses]

The short answer is you hone to return the cylinder to the finish and roughness that is correct per the ring manufacturer to facilitate proper ring seating(it varies with ring type). They get shiny over time, some cylinder wall/ring compounds more than others. Shininess isn't necessarily related to cylinder wear(which should always be checked) but a very shiny one with scuff marks and/or no crosshatch has a higher likelihood of being worn out of spec.

 

[steppinthrax]

The short answer is you hone to return the cylinder to the finish and roughness that is correct per the ring manufacturer to facilitate proper ring seating(it varies with ring type). They get shiny over time, some cylinder wall/ring compounds more than others. Shininess isn't necessarily related to cylinder wear(which should always be checked) but a very shiny one with scuff marks and/or no crosshatch has a higher likelihood of being worn out of spec.

How long does it typically take for the marks to go away?

 

[Ramses]

the crosshatch? varies a lot. I've seen them gone in 10K, seen them still there at 200k. some folks equate that to health or quality of the motor but I don't know that it's an absolute rule. it's nice to still see crosshatch, but unless it's uniform all around and up and down the cylinder it don't mean much to me, we still measure. cylinders don't wear evenly, more at top, or bottom, or middle, or on one side, etc, etc. depends on the motor.

 

[Pulsar]

Ramses covered it well. I actually handle the honing of cylinders where I work. The 'crosshatch' pattern is very specific - we measure the angle of the hatch and the depth of the hatch to the micron. Too smooth and it won't hold oil the way you'd like it to and it will increase wear on the rings. Too rough and the peaks poke through the oil skin and you get the same result - excess wear. If it's too rough the napier ring has trouble removing the oil on the down stroke and you may see additional consumption as well.

We expect our honing to be there for the life of the engine. If it isn't, then something isn't 'perfect' with your engine, but frankly it's not something you should worry about. It's just one more step us manufacturers have added to try to get these beasts to 300k.

 

[Ramses]

I actually didn't know the surface irregularities were specifically intended to stay beyond break-in but it makes sense reading that. Thanks.

 

[olds]

I understand the difference between cylinder honing (enlarging, correcting) v.s. deglazing (diy mechanic can do).
I personally wouldn't define honing as "enlarging". I'd call that boring.

 

[crashtech]

I've had cylinders re-honed to achieve a particular larger clearance, so honing is enlarging; it is the final step after boring to achieve the perfect piston to wall clearance as well as the right surface finish.

Sorry if I'm boring you.

 

[steppinthrax]

How about using deglazing stones at home vs taking it to a machine shop.

 

[Pulsar]

First, the manufacturers don't use anything called deglazing stones. There is a rough, semi-finish, and finish hone step that use varying-grit stones on specialized tooling. But it's all honing because we removing appreciable amounts (microns).

*shrug* I've never heard of deglazing but I don't deal with used engines much. I would question the ability to actually get a specific surface finish measurement and a precise crosshatch. We use hydraulic floating honing heads drive up and down a very specific rate with regards to rotation and we use a microscopic vision system along with a micron-accurate finish gauge.

I'd have a shop do it if you really want to reinstate the crosshatch. They can control speeds and feeds precisely. But that MAY be from the over-anal land of OEM =).

 

[crashtech]

How about using deglazing stones at home vs taking it to a machine shop.

Deglazing will result in an out of round, tapered, oversize cylinder that has been scratched up for new rings. Ring seal and oil control will be poor compared to a proper job, and there may even be piston slap if the old pistons are not knurled to fit the bore.

 

[Ramses]

I haven't seen anyone deglaze or run a ball hone in anything beyond a lawn mower in ages, and even the ones that did were doing it on very simple old domestic motors that really didn't need much in the way of oil control or compression to run along as well as they ever did. I'd still do it on a lawnmower, but that's about it.

What I was taught in votech was that if the cylinder is within spec as to taper and bore(or close enough if you were doing a quickie re-ring) then to hone with light oil to break the glaze and allow the new rings to seat. And it did in fact work, been done countless times but again on ooollld tech motors. Most motors, by the time they need rings anymore, the cylinders are going to be gone, rings wore a lot faster it seems like on old stuff. Modern fuel management keeps so much fuel off the cyl walls the whole bit last a lot longer in general. Same procedure with a tiny version of the same tool was taught for use on wheel cylinders and master cylinders and pretty much anything else with a cylinder to smooth and polish the surface. Nobody does that anymore either.

Ze Germans got into some interesting stuff with nikasil and alusil cylinder coatings, the old Porsche books have some nuttiness about using a cotton wrapped polishing hone or some other overly German thing. US gas ate a lot of that stuff right off the walls back in the 80's and early 90's, I remember BMW caught hell over the alusil I think it was on the M62 v8. I still see one occasionally that's just now giving it up that was never swapped out.