Assessing an unknown engine

[RobFrost]

This sprocket came away easily and I heeded Dempsey's warning to keep hold of the pin and not drop it into the engine.



This sprocket came away easily



There was no such warning about dropping the Woodruff key, although that should have been obvious to me to put the little magnet on it. It was quite stuck but I pushed it with a screwdriver until it suddenly yielded and gave way to the tinkling sound of metal landing in the engine case below. It was, of course, nowhere to be seen but thankfully a blind fishing exercise with the magnet came up successful.



Next came the shims - make a note which ones came from this side of the engine.



And this fat washer had a chamfered edge which face in towards the engine.



I was left thinking it was a lot easier for Dempsey to write "pry out the cam end cover with a screwdriver" in the book than it was to actually accomplish this feat in the real world.



I ended up taking the different route of removing the chain cover with the cylinder heads, before I realised you can actually access this cam end cover from the back to push it out.



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[RobFrost]

Dempsey says these chain guides are a single use item, but these appear to be brand new.



Judging by the nuts and some sealant around the rocker covers, I'm sure somebody's been in this engine during its 10 years of use. I'm guessing they had recently replaced these before the vehicle in which this engine was situated met its demist.

Following Dempsey, for a moment I thought I must have missed some steps, when I realised I was removing the cylinder studs not having removed the cylinder heads and rocker covers yet. But rechecking the book confirmed that's the way you do it.



That all came away nicely, and the faces of the valves which would not have been coated in oil, looked a bit corroded.



Getting a bit closer to the business end of things, what I thought on the bore scope looked like corroded pistons, appears to simply be carbon build up.





In fact a little later, a scrape with my fingernail and gentle rub off with tissue would reveal nice steel underneath.



I don't know if this is a shim or a gasket - is it original factory, or does it signify somebody's been carried out some work?



The barrels book a bit of freeing up with the old plastic mallet but a good pull and a wobble and the first couple came away. I wpied them with a tissue and I thought they looked good.



At this point, and this is very much a tentative view, I'm starting to think my fears about the state of the engine were unfounded and it seems to be in rude health - barely used, in fact.


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[RobFrost]

The pistons look good to me, a bit of varnish or something on this one.



And there's definitely some marking of some sort on this barrel.



I guess I should get an expert to advise me whether these need reboring or honing.

A friend of mine said he simply ran a stood engine for a while, which was spewing out blue smoke, and after a few miles it was like new again. The rings just needed to seat. I don't think I'll chance that approach on this engine.

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[RobFrost]

My curiosity has probably kept me going longer than I ought without having a tidy up. Everything is already going organised into freezer bags, but I'll probably go and sort some bench space for all the bits before going any further.

I'm also starting to regret not cleaning the outside of the engine better first, as the imperative to split the case is declining now, so the concern I may have introduced debris into it becomes more of a consideration. I'm almost thinking it might be better to not slide the other barrels off their piston rings.

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[911hillclimber]

You are right!
A good external clean would have helped, but now you are here, just tear the lot apart down to the crank. You need to check a lot more yet Rob, the intermediate shaft clearance and float and other things. The pistons will clean well, i think that bore will hone, but you need an engine shop to advise.
Valves should clean, but the seats?

The thin copper rings at the bottom of each barrel is right, but you need new to re-assemble, they are designed to cruch and seal from oil leaks.

Take a look at the repair 'kit' that Design911 sell for doing the top and the bottom of these engines, you get all you need bar the pistons and barrels.

Best to replace all bearing surfaces, shells to ramps to chains etc.

I've used their kits for my 3.2 and it was great.

Cleanliness is godlyness, clean once, twice and trice and then again.

I would be cleaning parts roughly as I bag them or you will be a right old mess, but that's just me maybe!

[RobFrost]

I note the top two rings here spring out.



While the top two here seem stuck in their groove.



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[RobFrost]

This one will not budge. Any suggestions are welcome, especially those known to work and not damage the engine.



For now, I'm leaving it with some penetrating oil to sink in.

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[Gary71]

Diesel has been known to loosen things off?

That and (maybe not at the same time!) heat around the edge of the piston whilst gently tapping it with the handle of a heavy hammer.

[911hillclimber]

That is correct Gary, also using auto box trans fluid, all good at seeping into closed gaps.
Bit of hot air gun always helps...

Rob, this afternoon roughly costed up the parts to rebuild my elderly 3.2 in my 73T.
About £2000 should cover it.
All costs from Design911 but there is a good discounts available at that spend, and 10% for PCGB members.

That should pay for putting the Lola in storage so to have the space to do the engine.

[RobFrost]

Rob, this afternoon roughly costed up the parts to rebuild my elderly 3.2 in my 73T.
About £2000 should cover it.

"Never again" I'm pretty sure you said last time.

Anyway, I think you should twin plug that one too.

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[911hillclimber]

I think I meant Never Again will I do a modiofied 911 engine, but a stock rebuild will be easy by comparison.

A nice reliable Clewett system would be good over the 1986 Bosche DME?
Don't think that will happen again in my garage!

You will need a lot of paraffin to rough wash those parts, the longer the soak the better, esp the heads.

Laid out, a 911 engine ready to build takes up a HUGE amount of bench space.

[RobFrost]

After making room for some of the parts, I turned the engine over today and removed the other rocker assembly. The left side of the engine tells a different story. These must have been the problems seen on the scope. Two pistons are broken where the exhaust valve cutout meets the barrel.

With both chains free I was able to put the belt pulley back non and give thr flywheel a gentle turn. It's clearly locked somewhere, but it wobbles enough to show the pistons on this side are moving freely in their cylinders, despite the broken piatons some discolouration possibly indicative of heat.





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[Gary71]

There’s no (visible) scoring on the bores from that damage?
Difficult to see from the photos, but is the top of the piston clean or is it some deposit build ups that then look like damage?

[RobFrost]

So that just leaves one cylinder on the engine, on the other side. Gently turning the crankshaft I was able to confirm it's this cylinder restricting the movement of the crank. I guess I'll add some more fluid and save that battle for another day.



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[RobFrost]

There’s no (visible) scoring on the bores from that damage?
Difficult to see from the photos, but is the top of the piston clean or is it some deposit build ups that then look like damage?

There's something there but I'd say it's more subtle corrosion. I think there is the slightest hint of a score although I only saw it once I took these photos. (All the same barrel).







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