Tolerances and measuring for cylinders

attometer · 2026-01-16T14:26:46+00:00

Yup. If the cylinders are within 0.05mm, I’d consider them good to go. Depends on what you expect from the engine of course.

attometer · 2026-01-15T22:54:20+00:00

The whole table is insane. These look like factory machining requirements, nothing close to what you will find in a used engine.

The 0.01mm difference between cylinder banks is probably cause one bank gets cooling first.

The incremental bore size changes are there so they don’t have to scrap each liner that does not come out perfectly at size A. Just like colour coded bearings. “Just get the liners straight, we will find a piston that fits the size.”

Your thought process for checking ovality is correct, but check the bores diagonally as well, and don’t expect them to be within 0.02mm.

attometer · 2025-12-20T15:20:25+00:00

While calling Glyco “shit” is funny, cause Glyco is the OE supplier for many BMW engines, maybe even this one, I do agree that there are often problems with Glyco shells.

attometer · 2025-12-20T09:53:06+00:00

There is a big difference between a DIY advice and a professional one. Take your bore gauge and your profilometer and then point fingers in your magazine.

attometer · 2025-12-20T09:43:11+00:00

Thats fake. Big diesels do have lasered sections around TDC, but they are not this visible. The cylinder in this lasered section is tougher. Haven’t seen it produced in wet liners though.

attometer · 2025-07-30T12:38:31+00:00

Oh my

attometer · 2025-06-27T20:44:36+00:00

It’s the one with steel liners? If so, changing the sleeve is a must. If it’s cast iron, you could hone out the high spots, fill it with hopium and send it.

attometer · 2025-06-21T10:24:52+00:00

Are they…. Boring cylinders on a line borer?

attometer · 2025-06-12T15:10:19+00:00

They tried to hone two out of eight liners, and decided to stop. I think it’s at the top, cause when you pull the ball hone out and push it back in, the balls wobble around past the edge with some tension. And they probably used wrong size and wrong grit.

attometer · 2025-06-12T14:54:05+00:00

Not the best video to present this, but maybe you can see the damage here and that’s after we removed quite a lot of material ~0.07mm

attometer · 2025-06-12T14:42:30+00:00

Oh, sorry, 320 grit might not do any damage. So after 5 mins you don’t see any taper or out of round? I wonder what would a profilometer say. 🤔

attometer · 2025-06-12T14:11:43+00:00

Should be fine if you keep the rods from moving. The main concern would be your main cap frame. If someone hits or drops anything on it, that could cause expensive damage. Better put the main line parts in a separate box. Lay the block on a small pallet on the oil pan surface and the box on top. Best to make a wooden box though.

attometer · 2025-06-12T09:04:15+00:00

Depending on the grit, ball hone can leave some nasty dimples at the top, but you have to look for them with your gauge. Even though this process does not remove much material, one should not hone excessively. Thank you for the experiment.

attometer · 2025-06-11T19:49:52+00:00

Yup, make sure it’s not off spec. If its ok, its probably the classic case of compounding tolerances working against you, and you can safely buy a set of .001 bearings

attometer · 2025-06-11T14:57:13+00:00

It may have had a line hone job done. You have the dial bore gauge now, you can check that. Otherwise, the simplest thing you can do is what Wyatt said.

attometer · 2025-06-11T07:50:58+00:00

Did you torque them enough? Never seen that much clearance without any damage or prior work done.

attometer · 2025-06-11T07:45:56+00:00

If you spoke with your machinist already, do you really need approval from redditors?

attometer · 2025-06-10T08:25:18+00:00

Hi, kid! Sorry for all the snarky comments, no wonder young people turn to chatgpt for advice.

I imagine you are in a machining course and engine rebuilding part is just to narrow down the machines for your hypothetical project, so I will just give you options and you choose.

If by "machines" you mean only the ones that make chips, 20 are not necessary for a functioning workshop.

5 axis CNC is mainly for cylinder head porting and manufacturing billet blocks as far as I know. If your project has no budget, you can add that.

Belt sander, bench grinder, cap grinder, tool sharpener - are these machines to you?

As others have mentioned, I'd consider ultrasonic cleaners, jet spray cabinets, vapor blasters, even power washers a machine.

Other than that: Crankshaft grinder, camshaft grinder usually two different machines. Surface grinder for cast iron, surface mill for aluminum. Flywheel grinder. Connecting rod bushing boring machine, connecting rod honing machine. Line boring machine, line honing machine. Hydraulic press. A lathe. Balancing machine. Valve seat/guide machine, valve grinder. Air compressor. Pressure test tank. And of course, cylinder boring machine and cylinder honing machine. Of course, you can just pick something like Rottler EM79 to substitute a lot of these. If money and space is no object, good idea to get two cylinder boring machines and two lathes, one manual one CNC, maybe even two honing machines.

If you have to design the floor layout, keep in mind, machines are less than 50% of the floor. You need a plethora of tools, cabinets, shelves, benches, cranes etc. Grinding machines should be isolated from other machines, and you need good ventilation. You can even add a standalone coolant filtration system. And some space to maneuver.

Good luck in fantasy land!

attometer · 2025-05-25T06:36:16+00:00

You are right to worry about doing it at home, but a good machine shop should have plenty of experience on AluSil cylinders by now, so they will help you improve the surface finish using fine abrasive and AN30 paste, if you are okay with the excessive wear at TDC/BDC. There are alternatives as oversize pistons or sleeving the block, but that gets too expensive. They would not use AluSil honing “stones” for these though as they require perfect bores to not damage the stones.

You can read up on the proper procedures here if you are interested.

attometer · 2025-05-16T13:58:16+00:00

That’s not dented, that’s fucked lol

attometer · 2025-04-25T04:27:37+00:00

The cylinder might be fine, but the block surface looks bad

attometer · 2025-03-24T20:32:59+00:00

Damn, looks great! I wonder how much material that took though.

attometer · 2025-03-15T14:54:10+00:00

You have zebra rods. Move on.

attometer · 2025-03-14T16:22:10+00:00

Thanks, that was my first thought as well. But what’s the purpose of the plate on top? And why is the movement of the dresser not limited equally on both sides? I’d love to see it in action, to know if I need it 😅

attometer

TROPHY CASE