Cylinder Hone Size

I'll be pulling pistons as part of an oil burning investigation on my '97 1Z. I expect I'll be re-ringing it, and would like to know what diameter "dingle berry" style cylinder hone to get. 3.25 -inch?

wikipedia says 79.5mm or 3.13" bore, so get a 3.25 or 3.5, whichever's cheaper. All the way up to 5" would probably do just fine.

If it is that far apart anyways I'd probably just send it off to be hot tanked, decked, align bored on the mains, bored to the next size of available pistons, and honed. Call around, local place here'll do all that to a 4 cylinder for $150.

Hello DR. VOLKS here I would never use a dingle berry hone they are junk.
I only use a K10 honing head same as a OEM honer. There are designed to keep the bore strait and round.
Bob Mann

If its burning oil and going through the ring, its probably going to need a bore job. The 1Zs did come with some crappy pistons so maybe you will get lucky.

On the 1Z this problem is not uncommon.
Some learned advice.
Keep in mind that at the bottom of the cylinder bore are the oil jet (spray) nozzles.
When using any type cylinder hone be very careful not to take the hone too deep or you WILL destroy the oil jets.
I use a card-board puck wrapped in duct-tape about 1" thick that I press down into the cylinder bore to protect the oil jets.
After I've honed the cylinder I wash the cylinder bore with diesel fuel to flush away any residual abrasive.
Be sure to use new rod bearings and new rod bolts.

My last advice....Be sure to mark each rod cap to ensure that they are reinstalled onto the correct connecting rod.

Just remove the oil jets for honing. Make sure you use lock-tite when you reinstall them.

One other rule of "thumb" that may be helpful: due to the tight tight tolerances and wear limits of our diesel engines- if you can snag the wear ridge at the top of the bore with a fingernail the cylinder is probably worn too far for honing alone.. meaning a bore and oversized pistons is in your future.

At the very least, if you've got a reasonable ridge at the top you'll probably want to do some careful measuring of each bore, looking for wear, taper, etc, before going to all the work of rebuilding with stock-sized pistons and rings.

CNGVW said:

Hello DR. VOLKS here I would never use a dingle berry hone they are junk.
I only use a K10 honing head same as a OEM honer. There are designed to keep the bore strait and round.
Bob Mann

Click to expand...

While I lean toward the if it doesn't need to be bored it doesn't need to be honed side of things, I don't see how you'd mess up straightness, roundness, taper, etc without going oversize.

If one thinks he needs to "break the glaze" they are fine for that.

Thanks for the responses...

I pushed the pistons out yesterday- they came out easily enough.
There is no discernible ridge and the bores look generally fine albeit glazed. I haven't measured them. The other thread I started on the job is here.http://forums.tdiclub.com/showthread.php?t=421520

I've decided to send the pistons/rods to Frank Irving (he already has the head)for evaluation- a couple of them do have minor scuff marks on them. I was careful to keep the end caps in order...

I have a 3.25 inch flex hone and may try it after I talk to Frank about rings. I'm sure I'll wind up measuring the bore over the next week or so if I can find the inside mics to do it with.

The squirters are a puzzle. The nozzles are missing (appear broken off and are MIA) on cylinders 3 and 4, but are intact on 1 and 2. I don't know the history of the car, but the previous owner did tell me he had the pan gasket replaced, so I don't know how that figures in. Seems very unlikely that they would just break off by themselves (or has it been honed before and they broke them?).

Missing jets would mean hot pistons which could deform and cause your problems.

How come you didn't do a compression check? I suppose a fitting that clamps in the injector hole since your plugs were stuck doesn't exist.

Can you still see the original honing marks?

No cross hatch, but zero ridge at the top. If I run the flex hone, I'll probably block off the cylinders somehow at the bottom to protect the squirters in cylinders 1 and 2 that are intact, then replace 3 and 4 after honing since there is nothing to snag now on those two.

I've been looking at the fasteners and they look like a torx fastener (?). T20 is a little sloppy. Does anyone know the correct bit?

I'd pull the other two just in case they were all poorly installed, and those two just didn't fall out yet or something.

Far as I know there isn't any in between from 20 to 25, the only oddball should be that F'in general motors Great Plan T27 bastard torx
Sure they aren't metric allen?

The fasteners backed right out, but # 4 can't drop down far enough to clear the crank counterweight. Here is the one from #3.



Looks different than the one below which is billed as fitting a 1Z. The ones on my car extend into the block in a separate hole unlike the banjo bolt style.
Maybe the dealer has them......

I spent three hours late this afternoon and evening measuring the cylinders and pistons since the tools I ordered arrived. The telescoping gauges were $16 and the caliper was $26 both through Amazon.

I made a cartoon to keep notes on and measured the bores in both directions at about an inch below the deck and again at about 3.5 inches down. It became apparent that repeatability is the trick, so for anyone considering this using telescoping gauges, my solution was to take the rings off one piston, put a ring into the bore, then use the piston to push the ring to the measuring depth. Then with the ring square to the bore you can rest the gauge there knowing it's close to perpendicular to the walls. Then to allow free movement of the gauge I would lift it slightly off the ring, and then just barely hold the handle and lock it down. I took many measurements in each location and took an average.









To me the results show very little wear or taper to the cylinders (even with the minor scoring on #3. The piston from that cylinder has a pretty noticeable scar on it, so since they all are worn (standard is 79.47 mm) I'm considering a purchase of 4 new standard sized Nural pistons from Rockauto. I think the pistons come with rings installed. That #3 cylinder was missing the nozzle on the oil sprayer too, and Frank Irving tells me that that cylinder typically runs hottest.

I'll hone the cylinders with a 3.25-inch 240 grit flex hone (when that tool arrives) just to cut the polish off the walls.

Your caliper is repeatable to .002 inches (.05 MM). You need a micrometer for these kind of measurements.

Snap gauges are used by turning the lock screw snug with them a little longer than the dimension you're measuring and then sliding them "over center" through the bore, so that you're sure to get the bore diameter at the moment that it is perpendicular to the axis of the bore. Youtube will give you a much better explanation of it. No need for the piston ring deal (in fact it is probably another point of entry for inaccuracies).

If you are buying pistons anyways just get it bored and be done with it. No sense putting new pistons in a bore that's already worn by any measurable amount given oversize pistons don't cost any more. Yes, you have to pay for the bore but if you plan on keeping the engine for 100,000+ miles then it makes sense to give it the best foundation possible.

That said, if you just want to run it for a few years and money is the primary factor then go for it with stock sized stuff. I never do anything that I don't plan on keeping for a long time myself, so it makes sense to spend the money now rather than later.

Thanks- I'll have a look at that method.
I do think with the number of samples I took, I got very close to accurate though. I will have at it again though just to be sure.

Well, we have become somewhat acquainted with this engine...

We have rebuilt the head and it was showing signs it lacked maintenance. There were hard, black deposits in the head. I agree the AHU pistons are comparatively poor

First, I'd like to address some advice posted here...

1. A dingle ball hone (ball hone)was NEVER INTENDED to straighten out a tapered cylinder bore. It is ONLY for glaze-breaking. A cylinder that is square and has little wear, a ball hone is the perfect device for preparing the cylinder for a new set of rings.

We own both styles of hones and use them appropriately.

The cost for a truing hone, like the Sunnen I use is $480 compared to the average ball hone, which is $35. The replacement Sunnen stones cost almost as much as the ball hone.. So, after measuring the top and bottom of your cylinder, skirt and wrist-pin dimensions, if you have more than .0015 taper, either fork over a wad of money or look for someone who has a good high quality squaring hone, not a dingle ball hone.

2. In my experience, if you torque the oil squirt to around 20 ft lbs, it is just fine and they will not ever come loose. The Bentley manual specifically says not to use any sealant, as it might glue the check ball closed and keep it from working at all.

I have seen good pictures of the #3 cylinder and now see the bore numbers for the engine and it's not good. In my opinion, if this engine is honed and rebuilt with new rings, it will burn oil excessively.

Here is your math for the #3 piston, which is the problem.

The top of Cylinder 3 is 79.55mm or 3.1319".
The bottom of the cylinder is 79.52mm or 3.1307".
That is .0012" of an allowed .0015" taper.
You could say, within tolerance. Personally, we call the limit at .001" and will true the bore.

Now you have to figure the amount of wear on the pistons. Piston diameter is measured 10mm from the bottom of the skirt at centerline.
The Average AHU engine pistons are 79.44 or 3.1275".
You calculate a measurement of 79.39mm or 3.1256".
By your measurements, your pistons have worn .0019".

The maximum allowed hone above stock dimension by VW's standard is .0035" . Before you have touched the bore with a hone, you are already at .00273" and haven't removed the vertical stripes in the cylinder. I am guessing it will take about .004-.008" to remove the damage. That puts you well past tolerance for piston/ bore fitment.

We recommend cleaning up the bore with a hone to see how far you have to go. If the cylinder walls will not clean up, pull the block and bore it to .5mm oversize and replace the pistons.

Just so you understand the dimensions, There are some pistons that are .25mm oversize. That is .010". By the time you clean the #3 bore, you will be that size; not that we recommend honing to the next oversize... We would bore to .5mm; roughly .020".

As for your broken oil squirts, good luck with that. We haven't had one of those in the shop for quite some time.

Well I guess the lack of maintenance was inflicted before I got the car. I've taken good of it. Anyway,thanks for the reality check Frank. I'll run the hone, see how it measures and looks, then go from there.

When I bought the car it had some kind of VO system on it which I removed. After removing the pistons last week I see the ring grooves though not gummy or sticky, do have a lot of carbon.

20 to 30 seconds with a 240 grit flex hone at about 700 rpm using my 3/4-inch drill. By the way, I realize that I have been double posting in effect too. Sorry about that.

How about a closeup of #3 cylinder walls? That is where the issue is.

The carbon deposits on rings is very normal. When we are dealing with WVO systems, what is abnormal is cylinder wear in line with the wrist pin sides of the bore. The black that is stuck on the head is sign of insufficient oil changes while using WVO. That is not to say a dino fueled car can't get black inside the head, but the deposits from WVO are nearly impossible to remove. The WVO systems require keeping up with oil changes. We have a variety of pistons we stock and balance against your rods or new rods.

If the engine were burning oil prior to your purchase, then I'd say the previous owner got all he could with WVO and sent it down the road. WVO cars should be worth much less because you can't expect to get the extreme high mileage without high maintenance and apparently, this did not happen with your car. The injectors and injector pump suffer, even if the oil change interval is precise.

Let us know what you need from us.

Are you planning to remove crank ??

All this work, may as well do complete rebuild at this point

Personally, I would send block to Frank as well. You seem very knowledgeable, but we know Frank is truly superior. If you plan to keep the car, let Frank reassemble engine !!