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[Kevin Wood]

Blimey! Last time I saw that it was on a Ford crossflow.

Has the bore survived? Look like there's some evidence of debris picked up on the skirt below the ring land damage but hopefully a hone will see the bore usable.

What's the other bank like? Oh, hang on..

[JamesV6CDX]

The bore appears to have escaped unscathed! There appears to be a very light visible mark travelling downwards, but it’s undetectible by a fingernail. My beemer has a much worse bore mark and never had an issue.

The other bank , oh hang on 

I must admit I’m somewhat nervous about installing pistons. I also don’t know how to disconnect the broken piston from the con rod in order to fit the new one.

I’m guessing the gaps on the compression rings should be 180deg apart?

YouTube videos make it look easy but I’m not sure how the reality is

Parts wise -

New piston (no doubt)

New rings for all 3 (instead of just one?)

New exhaust valves x 6 on order

Inlet valves? Not ordered yet as I know they are usually ok?

Bearings where the con rods meet the crank?

Bolts for said bearings?

Head gasket, bolts and various gaskets

[aaronjb]

Looks like the wrist pin is a press-in affair (no evidence of circlip/retaining clip in the pictures that I can see) which means pressing it out before you can do the oven & freezer dance to get the new one back in, I think

[Marks DTM Calib]

Warm up the inside of the piston skirt with a hot air gun and the wrist pin should just push out (might need a light knock), repeat to fit new.

If the big end bearing looks ok, re-use it.

Bores will need de-glazing so the new rings can break in.

Your choice on how many ring sets to replace, try here for parts:

https://www.enginepartsuk.net/

[JamesV6CDX]

Looks like the wrist pin is a press-in affair (no evidence of circlip/retaining clip in the pictures that I can see) which means pressing it out before you can do the oven & freezer dance to get the new one back in, I think

Might slip the local engineering shop a few quid to do that bit, then!

[Nick W]

Refitting the piston is a matter of using a well lubricated piston compressor, and confidently knocking the piston through it with the same heavy hammer and block of wood you used to remove it.


I know you're doing the job for several other good reasons, but realistically it's time for a replacement engine.

[Marks DTM Calib]

Refitting the piston is a matter of using a well lubricated piston compressor, and confidently knocking the piston through it with the same heavy hammer and block of wood you used to remove it.


I know you're doing the job for several other good reasons, but realistically it's time for a replacement engine.

Not sure I would totally agree there, any other engine will be an unknown.

This one, with not to much expense, well be of very known condition (plus its already had a new chain and guides etc which is a common cause of noise issues).

Head gasket set, rings, piston (even second hand would do give its a modern engine), chuck it together again and its good for 100k miles (which it probably won't ever get near)

[JamesV6CDX]

Refitting the piston is a matter of using a well lubricated piston compressor, and confidently knocking the piston through it with the same heavy hammer and block of wood you used to remove it.


I know you're doing the job for several other good reasons, but realistically it's time for a replacement engine.

My concern with a replacement engine is, will it soon suffer the same problems?

Cost wise I feel it’d be easier to fix this one

[LC0112G]

My early copy of EPC shows circlips holding the gudgeon pin on the Z10XE engine, but the online version doesn't :

https://opel.7zap.com/en/car/s07/e/1/15-1/
https://opel.7zap.com/en/car/s07/e/1/15-2/

What these do show is there are 4 different piston sizes (99,00,01) plus an 0.5mm oversize. There are also 2 (or 3) different piston ring sizes, and 2 different big end bearing sizes. The 'garage' way is to just replace what came out with the same and throw it back together. The 'correct' way to establish what you need is to measure everything - the bore sizes using the bore dial gauge and piston ring gaps as I described yesterday, and the bearing clearances using plasti-gauge. I'd be worried about out of roundness in bore #3. If its bad then the new piston rings won't seal properly and it'll use oil and possibly blow-by.

Given #1 was producing no 'thrust' and #3 reduced thrust, and knowing that these 3cyl things need to be revved to get you anywhere, and that they're lumpy as hell at tickover I'd be checking everything I could to make sure there was no damage due to out of balance operation.

When I recently re-built my LC engine, I bought loads of measuring sticks, and the more I measured the worse it got. I knew one piston had been replaced many years ago due to a timing chain break. However, when I measured the piston masses, the new one was almost 50g lighter than the other 5. They're supposed to be a balanced set (+/- 2g IIRC). 

As pointed out yesterday, where do you stop?

[Kevin Wood]

That is the issue, deciding where to stop.

Anything beyond slapping the same sized replacement piston back in is going to be an engine-out job to do properly.

The car is not going to become a timeless classic that you want to keep for 20 years, and it probably doesn't have enough miles left in the rest of the car to justify doing a maximal effort job on the engine.

I would be sourcing a piston and a set of rings of the correct grade, honing the bores and putting it back together, I think. Provided the bore wear is consistent with the 80k miles covered, I think that would see it out. Yes, you could do better, that's always true unless you return the engine to an as-new state (and you can go further than that, of course!) it is worth it, in this instance? No, IMHO.

[Marks DTM Calib]

The tolerancing has improved a hell of a lot over the last 30 years and all the GM engines have this sort of piston selection.

What you will find is a 00 marked on the crown, the bore will be bob on and the factory will never have used anything other than the 00 (based on my experience of pulling far to many cylinder heads and checking bores over the years)

[STEMO]

The tolerancing has improved a hell of a lot over the last 30 years and all the GM engines have this sort of piston selection.

What you will find is a 00 marked on the crown, the bore will be bob on and the factory will never have used anything other than the 00 (based on my experience of pulling far to many cylinder heads and checking bores over the years)

‘Bob on’.......now there’s a Dibnahism.

[henryd]

The bore appears to have escaped unscathed! There appears to be a very light visible mark travelling downwards, but it’s undetectible by a fingernail. My beemer has a much worse bore mark and never had an issue.

The other bank , oh hang on 

I must admit I’m somewhat nervous about installing pistons. I also don’t know how to disconnect the broken piston from the con rod in order to fit the new one.

I’m guessing the gaps on the compression rings should be 180deg apart?

YouTube videos make it look easy but I’m not sure how the reality is

Parts wise -

New piston (no doubt)

New rings for all 3 (instead of just one?)

New exhaust valves x 6 on order

Inlet valves? Not ordered yet as I know they are usually ok?

Bearings where the con rods meet the crank?

Bolts for said bearings?

Head gasket, bolts and various gaskets

I would deffo fit full set of rings(gives you a chance to check over the other two pistons),I wouldnt be changing bearings unless they are knackered and showing copper,big end bolts will go again

[Shackeng]

The appalling thing is that the garage put this back together and charged £1300 and change!
Send them a pic James, and congratulate them on their work.

[Field Marshal Dr. Opti]

£1370 and the car was returned with no compression on one cylinder.