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Fri May 10, 2019 3:56 am

I have found a very good deal on new KS oversized pistons which include rings.
Now I am searching for a machine shop. I was told that with these old diesels you can't just go to an ordinary machine shop because the tolerances are much much tighter than for with most modern engines. So I am not sure how to know if a machinist is good enough without specifically having a good recommendation from someone I trust.

I was told about a good machinist nearby who works alone in his own shop - so this is a guy I can talk to personally - and he will do the work himself. I am wondering what should I bring to him and what should I ask him in order to determine if this is the right guy? I guess I'd just bring my BLOCK, and maybe the CRANK and one of the old PISTONS?

Any thoughts?

Fri May 10, 2019 5:11 am

So I think I understand more now... for the prospective machinist I should bring to him my BLOCK and my CRANK and 2 printout pages from the manual.

So he should understand that the cylinders must be only 3/100ths of a MM wider than the new pistons.

He should also measure the 9 bearing surfaces of the crank to determine if this needs any machining.

...anything else to be concerned about?

Fri May 10, 2019 5:22 am

I would like to say engine tolerances are just that. Every engine ever made has tolerances. What makes one rebuild better than another? Tolerances. There is nothing unique to a vw diesel. Without looking it up, I’m sure the clearances are probably identical to a VW gas engine of that era. What has changed is the proliferation of aluminum blocks and multivalve cylinder heads. They have challenges that the old fashioned machinist might not have the tools or experience to do.

The machinist you choose just needs to be able replicate the original tolerances. The piston should have a build sheet with a recommended wall clearance and piston ring gap. If not, you will want to use the original clearances that the factory manual has documented.

The shop should be clean and organized. You won’t have a boring torque plate, so the final job will only be so good. I have the machine shop bore cylinders within .005” and the hone to the final clearance. The boring fractures the cylinder walls and by honing the above plus necessary clearance will give you the best finish. When I get my block back, I use a flex hone to get an even better cylinder wall finish. You can’t see or measure what I am talking about. It’s microscopic, but I bet you can find pictures online.

Figure out your list of measurements and clearances to bring to the machine shop and discuss those up front. This should give you some comfort level.

Sat May 11, 2019 1:53 am

OK, thanks Mark.
After talking with a few people I need to accept that 1) the machining tolerances are critically important, 2) there is not much I can do aside from try to choose a reputed machinist and then hope for the best.

I have been recommended a guy who works solo, so most likely I will let him do it >>> I will just impress on him how important it is for me that he does NOT over-bore it, and even offer to pay a bit extra for him to take extra time to be double sure the holes don't end up too big.

So I realize that I will have to take this one step at a time without fully knowing what the following step will actually be (I'm now getting used to this venturing blind into the dark unknown :D)

Am I correct to assume that my next steps are as follows:
1) take block and crank to machinist for analysis (to determine piston and crank bearing sizes to purchase)
2) order new pistons and bearings
3) bring block, crank, new pistons & bearings back to the machinist and have him do the machining work
4) ....after that??? study up on how to assemble, then assemble?

Sat May 11, 2019 3:01 am

Since you will have a strong un worn motor maybe you should also upgrade the injectors to ones with larger nozzles and get yer fuel pump upgraded, Giles. I keep seeing where people rave about vnt turbos with a control unit. If you go all out with those components you could have a contender, I would think. Anyway I appreciate that you are doing a thread on the rebuild process.

Sat May 11, 2019 3:37 am

ndorian wrote: Since you will have a strong un worn motor maybe you should also upgrade the injectors to ones with larger nozzles and get yer fuel pump upgraded, Giles. I keep seeing where people rave about vnt turbos with a control unit. If you go all out with those components you could have a contender, I would think. Anyway I appreciate that you are doing a thread on the rebuild process.

Thanks for these suggestions! My goals and priorities weigh in heavily on the side of reliability and longevity. Basically I just want to keep moving my hippy bus slowly down these old back roads of Europe hassle-free and cheaply. I am concerned that if I would increase the power of my engine it might stress out my old 091 gearbox before I also have the chance to rebuild that.

However, I am concerned about the injectors - I wonder if I should buy new ones? At a very minimum, while they are out I will at least take them to have them checked. I have a guy here who rebuilt my I.pump and did a great job, and cheaply.

Nothing to worry about regarding the HEAD since I have a brand new KS one... I assume there is nothing to do with that, lash checking??

One concern I have is that backing plate on the side where the belts are. My new block doesn't have this and the one on my current engine is bent and damaged.... maybe the thing to do is repair that if I can't source another one?

Otherwise vacuum pump, oil pumps get swapped over after checking. Probably get a fresh new waterpump and TB?

Swap over the turbo (I have a new K24 KKK on there)...

...what about gauges? Good to have an ETG?
...oil coolers??

Sat May 11, 2019 4:09 am

Bring him the block with main caps installed in correct order. Crankshaft, connecting rods, and intermediate shaft. He can check the cylinder bore and most likely will hone one cylinder to see if a first oversize piston will work. Because of the, you should remove the piston oilers from the block and set them aside for reassembly.

With the main bearing caps he can check the align bore. He can make sure the rod ends are to spec and measure the crank journals. Ideally the crank just needs to be polished. He can also check the intermediate shaft journals and bearings

Here most machine shops have a “bible” of tolerances, so he may have that on hand.

Fast forward, the head gasket comes in multiple thicknesses. The gasket you choose, is determined how high the pistons protrude above the block at TDC. You want the thinnest gasket that is called for. Don’t assume the gasket you removed is the correct thickness. The manual covers this.

Sat May 11, 2019 4:37 am

MarkWard wrote: Bring him the block with main caps installed in correct order. Crankshaft, connecting rods, and intermediate shaft.

The whole thing is now currently totally disassembled. When you say install the main caps - I should do that without the crank in there, no? [I hope I still have the correct order marked on my caps and pistons etc]

MarkWard wrote: He can make sure the rod ends are to spec

Is this a measurement I can look up and print out to make sure he has it? ...I'm still not even sure what the "rods" are yet > I will study up and also organize my "stuff".

EDIT: this is great, to be able to go there looking like I know what I'm doing! He will take me more seriously :)

Sat May 11, 2019 5:40 am

Assembled bare block. While the main caps are marked, wouldn’t be the first time for a machine shop mix up the order. Rods is short for piston connecting rods. The big ends need to be round and to spec. The small ends have bushings that most likely will need replacement and they would be fitted to your new piston pins. The machine shop will do this.

Sat May 11, 2019 6:22 am

If you clean off the tops of the old pistons you should be able to read the size numbers on them. I would do that first thing, looking at all 4 in case one cylinder has been bored more oversize than the others. There is a chance that one or more is already bored to the maximum. Hopefully it is all original bore and original deck height.

Mark

Sat May 11, 2019 11:57 am

Quick question....
when I put temporarily assemble the crank into the block for the purpose of taking it to the machinist, do I put the crank in WITH the old bearings? ...or just leave them alone?

Sat May 11, 2019 1:14 pm

Good news about the piston sizes... all 4 of them are 76.48 which is the original smallest size. You can see this number stamped clearly on each one.

Sat May 11, 2019 1:50 pm

You should definitely have the old bearings in place if you have the crank in the block. The bearings are softer material than the block or crank and without them you run a risk of marring the crank journals from contact with the block.

Sat May 11, 2019 1:59 pm

At the least you would want a bearing at each end.

Mark

Sat May 11, 2019 2:04 pm

That's what I thought... it doesn't feel right to put the crank in without bearings.

Sun May 12, 2019 12:41 am

OK, so if I understood correctly I should install the crank again with bearings (1 bearing on each end). Main caps should be in proper order. I noticed they are marked 1 thru 5... and #1 means the belts end.

So I should just clean everything really well, then re-install with a little bit of engine oil as lube, and then gently snug down the lugs > they don't need to be fully to torque, no?

Sun May 12, 2019 4:25 am

I would pack the crank and intermediate shaft separate. Wrap them in news paper. Bring a bare block with the main caps installed. The main cap bolts don’t need to be torqued.

What I always do when I disassemble an engine, once the piston and rods are removed. I turn the crank by hand to “feel” it. Someone with experience will know right away if the crank is bent or the crank bore is out of align. I also check the endplay. The main bearings take very little wear and might be better than what you can get in the aftermarket. You could decide to reuse them if you did not mix up the shells.

Sun May 12, 2019 5:20 am

MarkWard wrote: I would pack the crank and intermediate shaft separate. Wrap them in news paper. Bring a bare block with the main caps installed.

Aha... so I mis-understood. I thought the crank should be installed so he can rotate it to check something.

MarkWard wrote:
What I always do when I disassemble an engine, once the piston and rods are removed. I turn the crank by hand to “feel” it. Someone with experience will know right away if the crank is bent or the crank bore is out of align. I also check the endplay.

The history of this engine is that it was not used much. It was in the Fire Brigade somewhere in East Germany. Then a Czech guy bought it and blew the head gasket... the engine clearly has much less millage and use than my current JX.

MarkWard wrote:
The main bearings take very little wear and might be better than what you can get in the aftermarket. You could decide to reuse them if you did not mix up the shells.

The "main bearings" are all of these "shells"? Actually I still have them more or less in order --- but I think the thrust washers are mixed up.

Would it be worth to take detailed fotos of those and do my best to re-confirm their placement order?

Sun May 12, 2019 9:01 am

I still see the oilers installed. Remove them so they don’t get damaged. I also see the intermediate shaft installed. It should be removed. It rides on 2 bearing shells.

The crankshaft has main bearing shells. Grooved shell goes in the block saddle. Plain shell goes in the main bearing cap. In production VW used a grooved shell in the cap of number 4 only.

The other bearing shells are connecting rod bearings. One shell looks shined. The others look ok.

A machinist should be checking the crank bore with a gauge not feel. Feel is a good indicator that things are close, but a gauge will tell. Same with the cylinder bore. My machine shop uses the crank bores to center and secure the block for boring and honing the cylinders. That’s why they need the caps. If he misses seeing the oil squirters he will whack it with the boring tool. Good luck finding them. The blocks oil galley caps should be removed for thorough cleaning and drilled and taped to accept Allen plugs. They are dead ends and crud accumulates there. Don’t want that in your knew engine. Good time to replace the freeze plugs if they are rusty.

Sun May 12, 2019 12:29 pm

Yes those fotos are a couple of days old. I now have the oil jets and jack shaft out... have also cleaned up everything much better.

Are you saying that it might be wise to re-use all of those shell bearings?
I will take some closeup fotos....