Rover P6 2000TC - there will now be a short delay

[N Dentressangle]

37 minutes ago, SiC said:

I was surprised that those bearings were sufficiently worn to cause knocking 

Yeah, me too.

On the other hand, they were ready, so it wasn't wasted. Here's what Haynes says on the subject:

[SiC]

I agree, not a wasted job. A crank regrind or even replacement will cost far more than a set of bearings. Plus that sump needed dropping to clear all that shite in it anyway. 

[N Dentressangle]

So I'm cracking on with pulling the head. I'd expect this to be a swine of a job. On a Land Rover there would definitely be seized / sheared bolts, inaccessible bits etc. However, on the P6 everything seems to come apart exactly as you'd want it to.

I read the Haynes, which basically tells you in huge detail to remove everything you can see, and then got on with doing what was obvious. This didn't actually take very long:

The carbs themselves are a massive heavy chunk of kit:

Next bit is the part I'm not looking forward to: removing the tension from the upper cam chain, timing the engine up to marks then removing the head bolts.

[SiC]

I didn't actually realise (or remember) these were OHC.

Looks cheaper/simpler/less parts setup than most OHV top ends. 

Makes you wonder why BL didn't use this lump in other stuff when their B-series L/Triumph SC/etc tooling was getting knackered. 

[jonathan_dyane]

That exhaust manifold is a hell of a thing!

I hate to say it but I don't see an obvious explanation for tapping in the cylinder head, I suspect little end or damaged piston probably more likely..

[High Jetter]

1 hour ago, SiC said:

I didn't actually realise (or remember) these were OHC.

Looks cheaper/simpler/less parts setup than most OHV top ends. 

Makes you wonder why BL didn't use this lump in other stuff when their B-series L/Triumph SC/etc tooling was getting knackered. 

Heavy tho, hydraulic tappets were a pain. The V8 was way more attractive.

[N Dentressangle]

12 hours ago, jonathan_dyane said:

That exhaust manifold is a hell of a thing!

I hate to say it but I don't see an obvious explanation for tapping in the cylinder head, I suspect little end or damaged piston probably more likely..

Knackered cam bearing?

Also, the noise is far quieter once warmed up. Weird.

Anyhow, once I've pulled the head I'll be a bit further forward, and with the head removed I'm 90% of the way to pulling the engine anyway if there is some other cause.

[N Dentressangle]

Head is off, and we may have found our suspect.

Here's the head:

Nothing awful at first glance, but what are those light witness marks on the inlet valve of #3? Let's have a closer look:

The camera shows them as brown, but they're actually silver, where something has hit the valve.

Hmm. OK, what about the pistons?

You'd like a better look at #3, huh?

Fair enough:

I have no idea what that is. 

What are your thoughts? Have we found the problem?

[comfortablynumb]

Unless my eyesight is playing up, ( highly likely) that looks like the imprint of a nut?

Which begs the question, where's it come from, and where's it gone? 🤔

[N Dentressangle]

Shim on #3 inlet has also seen better days:

[captain_70s]

17 minutes ago, comfortablynumb said:

Unless my eyesight is playing up, ( highly likely) that looks like the imprint of a nut?

Which begs the question, where's it come from, and where's it gone? 🤔

Certainly seems so, and not a small one! A 1/2" for a carb fitting would be my guess.

[N Dentressangle]

17 minutes ago, captain_70s said:

Certainly seems so, and not a small one! A 1/2" for a carb fitting would be my guess.

Looks that way to me too.

No idea how that would have got in there - I haven't done any work on that area, and the airbox is held on with SU type sleeve nuts similar to the ones on a Mini air cleaner.

It does seem most likely to be the source of the noise though.

Question is what to do now...

[captain_70s]

Depends.

The photo almost looks like it's a raised section, like the nut has been pummelled into the surface of the piston. In that case you'd probably need a new piston. You could potentially grind the lump out, but I'd be worried about the remains making a bid for freedom if they come un-stuck...

If it's an impression in the top of the piston but the nut itself is nowhere to be seen than it is probably heritage damage. The engine has swallowed a nut, somebody has gone in and retrieved it, and then put the engine back together. I doubt it'd manage to find it's own way out past the exhaust valve.

In that case I'd probably just leave it as is -  It wouldn't be making noise unless a raised section was actively hitting something.

[comfortablynumb]

Can't really see on the photo, but how's the bore?

[Momentary Lapse Of Reason]

1 hour ago, N Dentressangle said:

What are your thoughts?

Mice? 🙃

 

Looks more like a washer than a nut to me.

Try picking around its edges.

Is the item raised above the block deck at TDC?

Look at the mark on the cylinder head beside the spark plug hole, is there any roughness there?

What was the big-end bearing like on that cylinder?

[SiC]

Is there cracks in that piston now?

 

[N Dentressangle]

Well spotted - it's quite possible, but hard to tell until the piston's removed and cleaned up.

Just had a chat with my local mechanic guru and showed him the pics.

He thinks that whatever happens, that piston needs to come out to check for damage / cracks, and also damage to the little end (which could be the source of our noise).

We can then replace the piston and gudgeon pin, as well as checking the rod for straightness.

Sound like a plan?

[jonathan_dyane]

I agree, it's ingested something.

Piston looks cracked, you will need to remove to inspect more closely. 

I suspect the new pistons will be expensive, if the bore is ok and there isn't actually a crack and the damage is localised to the top of the piston I would be tempted to 'reprofile' it with a file to smooth out the damage - you may be lucky but I suspect that the damage will be so significant the piston will be beyond redemption. If so I'd try for a good s/h piston or maybe another s/h engine to salvage the pistons out of. 

You will probably find when you take the pistons out some of the rings are badly worn or broken; might as well fit new rings regards when you're this far in.

If you do end up fitting one piston you should really weigh the other pistons to ensure the 'new' one is fairly close in terms of weight to the others.

[Dj_efk]

It looks like the nut has been partially melted and smashed into the piston to me.

[N Dentressangle]

14 minutes ago, Dj_efk said:

It looks like the nut has been partially melted and smashed into the piston to me.

That's also possible, isn't it?

Well, I'll hoike it out this weekend and have a proper look.

[N Dentressangle]

Piston extracted:

Cleaned the crown up, which actually looks OK:

Ingested a washer, by the looks of it.

No obvious play in the gudgeon pin. Not really sure what to do now.

Head refurb will be £150+. Ideally the crank needs a grind £250 inc bearings. New piston £100+

You can see where this is headed. Anyone know of a replacement engine?

[Bren]

27 minutes ago, N Dentressangle said:

Piston extracted:

Cleaned the crown up, which actually looks OK:

Ingested a washer, by the looks of it.

No obvious play in the gudgeon pin. Not really sure what to do now.

Head refurb will be £150+. Ideally the crank needs a grind £250 inc bearings. New piston £100+

You can see where this is headed. Anyone know of a replacement engine?

Chances of finding a  engine that requires no expenditure? Slim. Either way it's going to cost.

[MikeR]

are you not just tempted to pop the piston back in , its only the thick rim thats been marked , perhaps remove the pip just in case ..

and pop in the new crank and big end shells ...  should last a while .

and knowing whats what, keep an eye out for another engine /parts  ????

[Matty]

I'd agree with Bren. As a bare minimum an engine unknown to you you'd want a gasket set on it, new oil pump, water pump, mains and big ends. You've done a lot of this already. I think you've to just swallow the cost, much as it's a massive kick in the teeth. Proper shame pal but easily within your capabilities.

Onwards and upwards 👍

[captain_70s]

A washer is significantly thinner than a nut, if it was copper it'd have crushed quite easily. It seems to have embedded in the piston rather than bounce all over the place. Was it still in there?

If the piston isn't cracked I don't see why it couldn't go again. The cracking in the first few images seem more likely to be carbon deposits breaking away.

Any cheap replacement engine has a high chance of being worn out junk. I've yet to buy an engine that hasn't needed a full strip and rebuild, even low mileage units... Most of the £100-500 stuff is basically core parts.

In terms of the crank are the surfaces badly scored and have you plastigauged it to see if it needs reground? Those bearings aren't awful and it may well be the case you can just fit a new set of standard size bearings if the crank surfaces are decent.

It's also dependent on what your intended use of the car is. For local 60mph pottering you can get away with quite a bit compared to if it'll be doing 80mph on the motorway on the regular!

[N Dentressangle]

14 minutes ago, captain_70s said:

A washer is significantly thinner than a nut, if it was copper it'd have crushed quite easily. It seems to have embedded in the piston rather than bounce all over the place. Was it still in there?

If the piston isn't cracked I don't see why it couldn't go again. The cracking in the first few images seem more likely to be carbon deposits breaking away.

Any cheap replacement engine has a high chance of being worn out junk. I've yet to buy an engine that hasn't needed a full strip and rebuild, even low mileage units... Most of the £100-500 stuff is basically core parts.

In terms of the crank are the surfaces badly scored and have you plastigauged it to see if it needs reground? Those bearings aren't awful and it may well be the case you can just fit a new set of standard size bearings if the crank surfaces are decent.

It's also dependent on what your intended use of the car is. For local 60mph pottering you can get away with quite a bit compared to if it'll be doing 80mph on the motorway on the regular!

Thanks chaps.

It's already had a set of mains and big ends. However, I though #3 big end journal was marginal in terms of needing a regrind, and here's the new bearing after 80 miles:

Reckon I'll get away with it? Maybe, maybe not.

And I still don't know where the knock is coming from.

[N Dentressangle]

33 minutes ago, MikeR said:

are you not just tempted to pop the piston back in , its only the thick rim thats been marked , perhaps remove the pip just in case ..

and pop in the new crank and big end shells ...  should last a while .

and knowing whats what, keep an eye out for another engine /parts  ????

Yes, I think you're right.

Here are the piston skirts and bore for completeness:

Never let an engine stand for 17 years, kids.

I've done the bottom end bearings already, so that's sorted.

HERE'S THE PLAN

1. Linish the piston skirt so it's as clean as poss

2. Hone the bore and remove the marks

3. Tidy the piston up with the die grinder and re-fit it

4. Have the shims ground so the valve clearances are within range

5. Put the head back on with a new gasket

6. Write to Pope Leo and ask for a mention in his prayers

7. Hit the road

Sound good?

[SiC]

Would that chunk out not significantly affect the combustion flame front?

What about second hand piston?

[N Dentressangle]

4 minutes ago, SiC said:

Would that chunk out not significantly affect the combustion flame front?

What about second hand piston?

I don't think it'll make much difference - we're not talking about an F1 engine, or even one that's going to sit on the motorway for 20k a year. As long as it runs OK, I'm happy with that.

Finding parts for these engines is getting tricky!

[SiC]

Just now, N Dentressangle said:

I don't think it'll make much difference - we're not talking about an F1 engine, or even one that's going to sit on the motorway for 20k a year. As long as it runs OK, I'm happy with that.

Finding parts for these engines is getting tricky!

Yeah I agree performance isn't exactly an important point but thinking more that it could make it run rougher given an incomplete burn on that cylinder. Especially sharp edges that get hotter than others, potentially cause pre-combustion?