Assessing an unknown engine

[911hillclimber]

Well done Rob.
Need to get all the parts out and check the IMS gear wheel for damage etc., but looks like a good engine.

If it helps, when my 3.2 blew the alum grains were everywhere in the engine, oil cooler and all the galleries and pipes, just everywhere. I threw the oil cooler away as impossible to flush it clean and be sure I had.

The pump was full of fine alum gains but looked good, so i stripped and flushed it all out and re-used it. Gives 4 bar at 15000 rpm hot. For 2 years now.
A new one will always be a good thing.

Buy a good set of oil gallery cleaning brushes as you will need them.

What a crap rebuild effort it was!

[neilbardsley]

How can you rebuild an engine without cleaning it and leaving broken piston in it? Pistons changed without splitting the case and they thought they got away with it?

What do you think caused the oil starvation? Sealant or broken piston?

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[RobFrost]

How can you rebuild an engine without cleaning it and leaving broken piston in it? Pistons changed without splitting the case and they thought they got away with it?

What do you think caused the oil starvation? Sealant or broken piston?

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Looks that way - either replaced a piston without splitting the case. Or given the bearings look good, maybe they did a good job of a full revuild, but the chunks were hiding somewhere.

I think I'll know more once I've stripped and cleaned it. It's a bit of a mystery because there are clearly mint condition pistons and cylinders alongside overheated ones. I'm not that familiar with the engine design but the pump seems to be at the front and send oil down a galley towards the back. It's the back which appears to have overheated more. I even wonder if it was run with insufficient oil. Or even if the piston rings were incorrectly specified or badly fitted. They've been fatigued up the sides of the pistons on some, but others are normal.

The crank looks well lubricated though. I'm sure an experienced 911 engine person would know exactly what happened.

One con rod is a different colour to the others.

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[RobFrost]

I don't have any experience what the crank bearings should look like. All were seated properly, no rotation. They appear to be mint on the inside.



But on the outside they appear to show signs of oil erosion, which is a surprise to me. Is this normal?



This harks back to when I was splitting the case and I said the through-case bolts were surprisingly loose (but all consistently torqued). Maybe if those were too loose, the oil would pass behind these shells instead of into the crank journals?

Anyway, moving on the crank journals all look mint and measure to 57.025mm which based on a quick search of the Internet is acceptable?



Probably not quite the right tool for measuring it with but I was super careful.

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[RobFrost]

And 62.03mm across the engine bore although that was trickier to measure. Not sure what spec is. Maybe it says in Dempsey.



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[RobFrost]

After making up a cam nut removal tool today I found a bit of time to revisit this broken flywheel stud. After covering up all the journals and threads to protect from spatter, I welded the sheared head back on and it reversed straight out with the mini impact driver.



I used another stud as the earth to avoid causing any pitting to any of the crank surfaces.

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[Gary71]

Good recovery. I guess the heat from the welding was your friend here

[RobFrost]

No progress this past couple of weeks, as the good weather has had me doing other things.

But to catch up on some more of the dismantling... the cams are in great health, which is bitter sweet in a way because they'll be off to Newman cams for a mod solex grind, which is the direction I think I'm going with this engine.

This stud refused to come out, stripping the inner hex because there wasn't enough of it above the stud to take the torque.



Three nuts were sitting too deep. Maybe they were meant to be installed with a thicker washer? The washers were very thin.

I finally got the last one by cutting the centre out of an allen key so it would sit deeper in the nut.



The stash of parts is building up on my new shelf.





Used nearly a hundred ziplock bags so far.



The rocker arms and shafts seem in good health and a snug fit, but Newman say they will need machining to make sure they're spot on, to prevent uneven wear on the new cam.

It didn't show in the photo, but cylinder numbers are scratched into the top corners of the heads, confirming once again the engine's been apart before.



Can't remember if I posted this before but the IMS gear is all good.



And I've ordered some micrometers to take various measurements on the crank and case. I need to do some research, and possibly engage my ingenuity to think about how to measure whether it needs a line bore.



Also, advice is to pull the studs from the case and put case savers in. They seem so solid and in so well, it seems unnecessary and runs the risk of creating a problem out of nothing. But I think I have to defer to the experience of the experts.

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[911hillclimber]

Just my 2d worth:

When I did my 2.4 T/S engine in '92, Bob Watson said leave the studs alone. Mag case '7R' .

The studs etc were all stock and looked good, and I think that make the decision.

If your studs look corroded and the head threads look damaged etc then i would be tempted to time sert if you are changing the head long studs on the engine, ARP studs are £££££ so a careful consideration.

Possibly, the case threads may get compromised when you remove the stock studs, magnesium is a strange metal and not that robust.

As the engine has already been opened, the builder may have changes some/all the studs, so look carefully.

If i were you I would decide if the studs are good to use and if so leave well alone. Were the head tube nuts all tight when you removed them?
If one or a few were loose then look super carefully at the block/stud area for studs pulled.

iirc you can gat an idea of flatness in these spots by a good steel straight edge laid across the block and see if there are any high spots.

Can't help but think studs pulled are due to poor wrenching of the head nuts.

I read the Dempsey book on all this last night, but it seems he does not advocate to change the studs unless damaged.