question on (piston crown - top of cylinder block) clearance

[Gabri3l]

Hello all,
I got myself into a bit of a mess. I decided to rebuild my 2.0T (BUL) engine.
Long story short, the engine block and cylinder head ended up being machined. It wasn't my idea at all, but I was advised to skim the head as well as the top of the block, just to make the head sit better. The engine's original problem didn't have anything to do with the gasket but I accepted doing it just for the sake of doing the job only once the proper way. I wanted to avoid building and rebuilding just because of the head not sitting correctly. The problem now is the following. I've just fitted the pistons back in, and the clearance is absolutely non existent. Moreover, there is a protrusion that can be seen and felt (probably about 0.2mm, I haven't measured yet). The workshop says they took 0.006in off the cylinder block, which equals to roughly 0.15mm. I didn't take the measure before giving it to the workshop, but given the state everything was in, the the bearings, rods, pistons, etc being genuine, I would bet all my money on the engine having never being opened. In the end, something doesn't add up. Does anyone know with any degree of certainty what the clearance is from the factory between the top of the piston and the top of the engine block?
Thanks to anyone reading !

 

[Charlie Farley]

Can I ask, why did they skim the block?

 

[Charlie Farley]

The EA113 block is cast iron and very resistant to problems. The head, being aluminum, is less reliable; hence, skimming is only recommended for the head if warped and within sericible limits. If it was out of serviceable range and the block was ok then a new head would have been the preferred route to ensure correct fitting, with a proper new thickness head gasket to compensate for the skim.
Ive not come across many owners that skim the ea113 cast iron block block as well unless it was seriously damaged.

 

[Charlie Farley]

I'm pretty sure I have the engine clearance data spec on my laptop, will have a look .

 

[Charlie Farley]

Maximum permissible deviation of the lower mating surface of the cylinder head from flatness, mm — 0.05

Minimum permissible cylinder head height, mm — 139.2

Maximum permissible radial runout of the camshaft (with the rocker arms removed), mm - 0.1

Maximum permissible axial runout of the camshaft, mm - 0.035

Valve plate diameter, mm

• Inlet valve - 33.85±0.10
• Exhaust valve - 28.00±0.10

Valve stem diameter, mm

• Inlet valve - 5.98±0.01
• Exhaust valve - 5.96±0.01

Valve length, mm

• Inlet valve - 104.0±0.2
• Exhaust valve - 101.9±0.2

The angle of the valve working chamfer is 45°

Operating pressure of piston cooling nozzle safety valves, bar — 1.6÷1.9

Axial clearance of connecting rod bearings, mm

• New - 0.10÷0.35
• Limit - 0.40

Radial runout of connecting rod bearings, mm

• New - 0.02÷0.06
• Limit - 0.09

Piston ring gap (at a distance of 15 mm from the lower edge of the cylinder), mm

• Compression (new // limit) — 0.20÷0.40 // 0.8
• Oil scraper (new // limit) 0.25÷0.50 // 0.8

Piston ring groove clearance (new ring // limit), mm

• Compression 0.06÷0.09 // 0.20
• Oil scraper 0.03÷0.06 // 0.15

Crankshaft axial clearance, mm

• New - 0.07÷0.23
• Limit - 0.30

Radial runout of crankshaft, mm

• New - 0.02÷0.04
• Limit - 0.15

 

[Gabri3l]

Can I ask, why did they skim the block?

Hello Charlie, I was advised to request it. The person who did it doesn't have experience with engines this new (no joke there). I wasn't even planning on doing it before I was told

 

[Gabri3l]

Maximum permissible deviation of the lower mating surface of the cylinder head from flatness, mm — 0.05

Minimum permissible cylinder head height, mm — 139.2

Maximum permissible radial runout of the camshaft (with the rocker arms removed), mm - 0.1

Maximum permissible axial runout of the camshaft, mm - 0.035

Valve plate diameter, mm

• Inlet valve - 33.85±0.10
• Exhaust valve - 28.00±0.10

Valve stem diameter, mm

• Inlet valve - 5.98±0.01
• Exhaust valve - 5.96±0.01

Valve length, mm

• Inlet valve - 104.0±0.2
• Exhaust valve - 101.9±0.2

The angle of the valve working chamfer is 45°

Operating pressure of piston cooling nozzle safety valves, bar — 1.6÷1.9

Axial clearance of connecting rod bearings, mm

• New - 0.10÷0.35
• Limit - 0.40

Radial runout of connecting rod bearings, mm

• New - 0.02÷0.06
• Limit - 0.09

Piston ring gap (at a distance of 15 mm from the lower edge of the cylinder), mm

• Compression (new // limit) — 0.20÷0.40 // 0.8
• Oil scraper (new // limit) 0.25÷0.50 // 0.8

Piston ring groove clearance (new ring // limit), mm

• Compression 0.06÷0.09 // 0.20
• Oil scraper 0.03÷0.06 // 0.15

Crankshaft axial clearance, mm

• New - 0.07÷0.23
• Limit - 0.30

Radial runout of crankshaft, mm

• New - 0.02÷0.04
• Limit - 0.15

Thank you for your response. I should've said I've got all that from the service manuals (erwin). But unless I'm missing something, I still can't find the piston-to-top-of-block clearance

 

[Charlie Farley]

It's not unusal to have both skimmed in other cars to optimize a good fit but given the audi EA113 blocks reliable design etc they rarely suffer from warping , if anything its the head that does.

 

[Charlie Farley]

Thank you for your response. I should've said I've got all that from the service manuals (erwin). But unless I'm missing something, I still can't find the piston-to-top-of-block clearance

I'll check .

 

[Charlie Farley]

Assuming you obtained the correct thickness head gasket now required, well depending on how much was removed in total, otherwise the factory item should be ok if it was within factory tolerances.

 

[Gabri3l]

Assuming you obtained the correct thickness head gasket now required, well depending on how much was removed in total, otherwise the factory item should be ok if it was within factory tolerances.

I got a 1.3mm gasket from febi. The original seems to be 0.9. If the workshop tells me they took 0.006in from block and 0.005in from the head that adds up to 0.011in (or less than 0.3mm). My new gasket is 0.4mm thicker than the old one. Up to here everything is alright. The problem comes because after installing the pistons I've got them above the top of the block by roughly 0.2mm. That alone is 0.008in. Either the workshop is talking nonsense or my math have a problem.
In the very best case scenario, I can assume that the protrusion is exactly 0.006in and that the pistons where flush with the top of the block before the workshop. But I find that difficult to believe. Knowing the clearance from factory would help me out figuring out how bad it is compared to what originally was.

 

[B7Tourer]

I have no experience with the petrol engines but I know for a fact that the only solution for a warped head on the diesels is a new one. The heads are coated against porosity and they must NOT be skimmed. Added to which any skimming whatsoever may not be able to be compensated for with available thickness of gaskets, which is what you are now perhaps finding.

 

[northpole]

Actually on a petrol that rule doesn't apply, the head needs skimming if the mating surface isn't flat. See the previous reply from @Charlie Farley ... they should've left the bottom block alone the only thing needing skimming is the head... if the mating surface of the head is warped than you need to replace the bottom block, because once that warps it might crack (or worse) under pressure. I wonder if they might have put the pistons in the wrong way around... I think that's why it's protruding ever so slightly.

Can't think of anything else, as i've seen this before on one other engine, the 1990 2.0 16v ABF vw golf gti engine.. the pistons on that one need to be fitted the right way around, put them in 180 degrees out and they protrude.

Do you have a picture of the engine right now? in particular a picture of the bottom block with the pistons?

 

[Gabri3l]

Thank you all for the inputs. This was my mistake from the beginning because I should've checked for warped surfaces on the head as well as the deck, instead of blindly doing what I was advised. After all, I measured almost everything else.. The car has 230K in the clock, but apart from oil leaks and other neglects from previous owners, the engine was in great condition. Crank, cylinders and pistons well within tolerance. I dare to say deck and cylinder head were very much alright too. This weekend I'll try to measure piston protrusion accurately and see if I can find a suitable gasket for it. I'll let you guys know how it went. Thanks for the help !

 

[Gabri3l]

Actually on a petrol that rule doesn't apply, the head needs skimming if the mating surface isn't flat. See the previous reply from @Charlie Farley ... they should've left the bottom block alone the only thing needing skimming is the head... if the mating surface of the head is warped than you need to replace the bottom block, because once that warps it might crack (or worse) under pressure. I wonder if they might have put the pistons in the wrong way around... I think that's why it's protruding ever so slightly.

Can't think of anything else, as i've seen this before on one other engine, the 1990 2.0 16v ABF vw golf gti engine.. the pistons on that one need to be fitted the right way around, put them in 180 degrees out and they protrude.

Do you have a picture of the engine right now? in particular a picture of the bottom block with the pistons?

Thinking now, I wouldn't even have skimmed the head.... I don't have any pics of the pistons fitted actually. But I am sure to have fitted them in the right position. They were never separated from the rods. So, clues: arrow pointing towards the crank pulley on piston head, intake valve groove on the intake manifold side (also on the piston head), a dot in the rods facing the crank pulley... Too many things to miss