2.0 8V bottom end rebuild (by idiots)

[Dieselman]

A better video for the home mechanic, though I would still use a separate flat surface, such as glass for the sanding part.

At the end of he day, as long as the head is flat and smooth, it will work.

[bump_drft]

Thank you for all that

The main issue we see other than the head gasket is this pitting in the cam



The only replacement I've seen has similar pitting unfortunately

Trying to suss out how much is normal on a motor such as this

[bump_drft]

I think the head gasket failed more recently, as it only started showing symptoms of low compression recently. It happened quite suddenly and I only did two trips to two car shows on it, so hopefully damange is minimal. Bores look good but the pitting in the cam is worrying. I've yet to see the condition of the bearings.

[Dieselman]

The cam has obviously been starved of oil, check the tappets also.

I wouldn't think obtaining a cam will be too difficult, the R6a engine was the most widely used for Series 1, Xm. It may be possible to have that cam reground to the original contour, but you would need to use thicker valve shims.

[eyesoreracing]

Did a bit more work on the Xm today. The head gasket failure point did not cause any erosion of the head or block, just a little carbon buildup.

We stripped the head down a bit and will send if off to get resurfaced and probably some valve stem seals and clean up of the valve seats. I would have lapped them myself, but the recessed valve springs aren't compatible with any of my valve spring compressors, so its easier to just have it done at the machine shop.

We popped out one piston (#3) just to confirm they looked as good as the bores suggest.



No lip at the top of the bore, crosshatching still shows. Looks pretty good.



Piston skirts look good, no scuffing. Rings have plenty of spring to them and there's no carbon buildup in the ring grooves.



Rod bearings are toast. They've lost their shape and fall out of the caps. Luckily the crank side looks fine. Don't even really need to sand them. Just gonna throw in new bearing shells and call it good.



Main bearings look only mildly scuffed. We have a new set, though, so we'll throw in new shells in the bearing caps at least. With the cap side looking this good, I don't think the block side of the bearing will be bad enough to justify the work to get it out.

This engine was accidentally run out of oil recently, so the bearing damage isn't hugely surprising. Its not terribly clear what caused the oil to get so low, though.

[Dieselman]

The pistons and bores appear perfect, shows the advantage of cast iron blocks.
A good bit of progress, it shouldn't take too much to get this running again.

While the sump is off, check the dipstick length is correct, then remember to use it.

[eyesoreracing]

At one point we thought we heard rod knock on this engine, but listening closely, if you aligned your head with the flywheel, you could clearly hear the knocking noise was coming from the transmission side, not the engine side. If you put a long steel extension bar up against the engine and put your ear against it, you heard nothing. But do the same with the transmission and the low knock-knock-knock was clear. So something seems off in the transmission, but it isn't clear what.

Here's a quick clip of me grabbing the input shaft and finding no play in the shaft at all, but a good bit of backlash noise if you rotate the shaft. I didn't check which gear it was in. Oops..

https://youtube.com/shorts/VeMZsegUW3c? ... sBrb1xYzJB

Are there any obvious common issues with these transmissions? Or is that backlash noise a giveaway?

[Dieselman]

Your manipulating the gearbox input shaft doesn't reveal any bearing play, but that's not impossible, though note the hydraulics regulator is mounted on the front of the bell housing.
The regulator is a mechanical device and they do clunk as they switch between pressurising and free cycling the fluid. The pump will also have a rhythmic clatter/knock as it pressurises, then go quiet for free-wheeling.
It's possible the noise you are hearing is just the hydraulics operating. Run the engine with the pump belt off and see if it is quiet.

Other noises in that area can be slow, uneven idle causing gearbox chatter and noisy clutch pressure plate springs. I wonder if the unequal cylinder contribution due to blown head gasket, was causing the crank to oscillate and make the gearbox chatter.

I took another look at your big end bearings image and would advise polishing the crank journals as there has been material pickup from the bearing, which may cause roughness on the journal, which could ruin the new bearings.

Is it you doing all the work, or are you receiving some assistance?

[eyesoreracing]

The car actually belongs to @bump_drft, and I am the assistance. Poor bastard couldn't afford better help...

[eyesoreracing]

Regarding the transmission noise, it was a deep, low-frequency noise (not the clatter you hear when I rattle it by hand) and had a once per revolution rhythm to it. Rod knock tends to get dramatically worse when you rev the engine, often when you're coming off throttle at the top of a throttle blip, since the inertia loads are high and the combustion pressure isn't holding the rod down, making it easier for piston inertia at the top of the stroke to pull the rod up and clunk the bottom of a loose bearing against the crank. No such RPM sensitivity to this noise. It was mostly noticeable at idle, as I remember it. We picked up on the noise before the head gasket was obviously blown, but it could have been just starting at that point.

If there isn't an obvious common problem with these boxes that needs to be addressed while we have it in hand, I'm inclined to focus on the engine and hope for the best.