Embarking on an engine rebuild journey - some advice needed

[siLc]

When I installed T10171A to hold the camshafts in time, there is indeed some droop in the chain between the camshafts. But anyway, the head is now off. Cylinder walls are in excellent shape. I removed piston 2 - piston rings appeared to move freely. The oil control ring seemed to be slightly coked. Almost no wear on the bottom rod bearing, some wear on the top bearing. Will have to get a valve spring tool to see how are the valve stem seals. Looking for a reasonable machine shop to clean it up, replace valve guides and stem seals.

A little video about the cylinder head removal ->

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Immediate plan is to:

• Clean up the pistons
• Replace piston rings
• Replace rod bearings

If the rod bearings are fine, it wouldn't be bad to leave the crankshaft bearings as they were?

 

[siLc]

I took out all 4 pistons and the rod bearings all had the same wear pattern - top with some wear, bottom no wear. Before putting the pistons back in with new rings and rod bearings, I was advised by @golfi_vend to check the cylinder bores with a bore dial gauge to see whether the bores are in spec. Otherwise I would still have oil consumption. Since obtaining such tools takes some time, I took the top ring off of piston 2, put it into the cylinder 2 bore and noted the ring gap. The gap seemed slightly narrower on top and bottom, and a bit wider in the center of stroke. Obviously, not going to condemn the block on a visual observation.

The spec for the bore diameter is 75,61mm. The difference between spec and actual must be no more than 0,08mm. What's your take on this?

 

[RGH0]

Get some one with a bore gauge to measure the bores properly. get some one with a profilometer to measure the bore surface finish property. You may need a rebore and hone and oversize piston install. Any good engine machine shop should be able to do this

 

[siLc]

I ran my index finger nail up and down the bores and it didn't catch on anything, if that says anything about the condition of the cylinder walls.

 

[RGH0]

says it is possibly to smooth but without proper measuring equipment your just guessing

 

[Crasher]

If there is little or no wear, a quick home to put a nice 45 degree cross hatch is recommended. A couple of passes with an oiled medium triple stone on this 140k mile S2 block I built recently, barely showed a TDC shadow.

This is a plateau honed bore in a 1.8T block taken out to 83mm.

 

[siLc]

So I had my block measured and generally cleaned up at a reputable local machine shop. The cylinder bores are perfect with almost no wear, but honing was suggested, though a bit expensive at that particular shop. So I went to another one, handed over the block and after an hour or so received back a honed block and with the head gasket sealing surface nicely prepared. In total at a cost of 170€.



Now I can send the head off to a smaller shop, which specializes in cylinder heads, and also start to reassemble the block. Putting the order together for the massive amount of new one-time-use bolts is dizzying

 

[golfi_vend]

We have done many with genuine and AMC heads and they were all as good as they get.

Replacing yes, machining no.

 

[Crasher]

In the case of a Diesel, yes but I mistakenly thought this was a Diesel, skimming petrol heads is OK by VW.

 

[siLc]

Some progress. The crank is now in, with all new Mahle bearings (incl. thrust washers) and new original bolts torqued to spec (50Nm+90deg) in the correct sequence (inside out clockwise). Preparing pistons for installation - there are three rings, two compression and one oil scraper ring, which is a three-part ring with two seperate ring gaps for the top and bottom oil scraper rings. How should the rings gaps be placed? 120 degrees for the compression rings and anywhere for the oil scraper ring (in relation to compression rings)?

The head is at a machine shop waiting for it's turn. Hopefully it will just need a cleanup and new valve stem seals. Intake seals were some 0,25€ per piece for Elring brand...for CNG engine exhaust it's advisable to use original seals, which are a eye-watering 10€ per piece and there's 8 of them

 

[RGH0]

For the oil scraper rings I normally put the rings gaps of top rail, spacer and bottom rail 120 degrees apart and offset from the compression ring gaps. However as all the rings rotate due to the cylinder wall cross hatching they don't stay in that starting position for long

 

[siLc]

Thanks! So far I've pretty much left no stone unturned, but it occured to me that I've neglected the piston wrist pins. Manually cleaning the pistons up has resulted some debris on wrist pins' visible parts (next to the retaining clips). Should I take the wrist pins out, clean and re-lube? Or simply blow debris off by shop air and/or brake cleaner and reapply motor oil?

 

[Crasher]

If there is no play, just fit new rings.

 

[siLc]

My question was rather aimed at what level of cleaniness to maintain.

 

[RGH0]

absolute cleanliness is required when building an engine. Are the wrist pins a press fit into the piston or small end or located by circlips and free to move. If floating pins located by circlips then i would remove and clean. if a press fit then removal may be an issue

 

[siLc]

Fortunately the wrist pins were a snug fit and came out OK.

 

[Crasher]

Cleanliness, to the extreme. After honing, I clean the bores with brake cleaner, then thinners and then with Marvel Mystery oil. I use white lint free towels and clean from top top bottom over and over again until the cloth stays white. Then I rub the bores (with gloved fingers) using Molybdenum Disulphide ring seating powder, my personal favorite is by Total seal

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Unless it turns green, start again. I used to use Red Line assembly lube but I have rather fallen for Torqo since RL was out of stock.

 

[siLc]

I just use fresh motor oil (Castrol Edge 5W30 LL) for lubing the bearings and cylinder bores, as these kind of specialty assembly lubes aren't readily available here. I took the block with crankshaft and piston number one installed to get the rear main seal and needle bearing installed. Those buggers need tools which I do not posess. First piston was installed because rear main is installed with the first piston at TDC and I was too busy to properly install the rest - rear main includes the crankshaft speed sensor tone wheel, which needs to be installed at first piston TDC.

Now I can install the other pistons...and keep waiting for news about the head.

 

[Crasher]

You can get WD40 though, or similar? I NEVER use synthetic to build an engine, only mineral.

 

[RGH0]

I use Redline assembly lube on bearings and cams and followers, you can order it on the internet. What you use on the piston bores is not critical as its just to stop rust until the engine is started but use proper running in oil for the engine when you first run it.