Special getting closer...

[impmad2000]

Ouch !

[911hillclimber]

It got worse as the day passed by down to the crank.

Now I know why I couldn't find the piston skirt, it is literally in a Gazillion fragments EVERWHERE inside the engine.

Damage:
Piston(!)
Cylinder
Con rod
5 inlet rockers broken
5 inlet valves bent

Suspicious of:

Oil pump
Oil cooler

Matt/Gary:

Pin in one piece, that is the top half of the piston, nothing left of the lower half and nothing of the pin holes either!
Failure mode? I'm still thinking.
Look at the HOLE in the side of the barrel and it is split right down it's length. Looks more like a 500 bhp turbo bang than a stock 3.2.

It sure was going well just before it let go...

[Gary71]

What about:

Piston seized about half way into the stroke, rod bent, then pulled the bottom of the little end off on the way down and continued to beat it to death before you turned the engine off. Not sure why that would bend the other valves though...

I guess you are after a new engine now then?

[911hillclimber]

The other valves/rockers failing on the other bank of the engine is a real mystery!
All rockers are snapped clean as a whistle, worst valve is bent 3mm and all bent valves are inlet and a small mark on the piston.

There are a number of options:

Rebuild 1
Bob and Mike have parts for me so not a problem.

Rebuild 2
Do a 3.5! huge cost and hard to justify to myself let alone the Boss.
P&C + duel plugs for 300 bhp at best, so about 5K for 50 bhp!

Rebuild 3
964/993 engine on PMO.
3.5K off ebay for the engine (risk) and a whole lot of work to do it.
Solid 300+ bhp.
Clutch adaptation to the 915?
Will my headers fit?
Will the engine mounts be the same?

Option 1 is winning so far, about £1500
There is the 3.4 of course...

[Matt black70]

Blimey, that's one hell of mess.
But why so many rockers broken?

[911hillclimber]

No idea!
Rod bolts all tight, and the damage is in #4 but rockers 1/2/3/6 broken, so will change all 6...
Bits of cast piston everywhere and I'm not sure where the ringsa are, but the oil control rings are in the bottom, some of the top rings still in the crown.

all ideas welcome.

[haasad]

Under reading rev counter ?.......

Crikey thats a mess good luck with the re build. All those broken rockers is odd, shot in the dark but some kind of secondary failure in the valve gear drive?

[Gary71]

Has the cam timing slipped? I can't think of anything else that would take out that many valves/rockers.

[hot66]

would assume timing chain has jumped / snapped ? Or has the crank timing gear been damaged / failed

[Lightweight_911]

It's odd that the inlet rockers that have broken - I thought that it was usually the exhaust rockers that broke first when the engine is over-revved.

How old were the valve springs ?

Are the camshaft nuts still tight ?

What's the aluminium intermediate gear like ?

[911hillclimber]

You are all getting closer!
After stripping down #4 to see the damage I went to 1/2/3 to finish off the strip to the crank.

The chain was very tight on the lower side to the cam sproket and very loose on the tensioner side.

I think the piston skirt fragments made it's way to the other side of the engine and wedged the chain/slipping a link or so.

The timing dowl pin is ok, the woodruff key is all there to (not sheared).
i was very surprised to see the rockers snapped off, one half I couldn't find for a while!

The inter drive geat looks perfect!!!!!
#4 is right next to it and the skirt must have showered down while the crank shreadded it to death.

The engine was not on the limiter on this run, but 5500 would be about right and full throttle.

The stripped engine will go to Bob's for a mega wash, i will never get it all clean. Oil pump needs stripping too...

As to having a trophy shelf of such 'hard-luck' awards, I have a good head start.

[MikeB]

Methinks that the best use for it all is a table lamp from the flywheel and crank, an interesting wine rack from the case and 5 ash trays from the remaining pistons

There was a heck of a lot of stress going through it all during those last couple of seconds of use.

[Matt black70]

Mikes got a point graham, hasn't someone got an engine out there for you thats got a known background and/or build history.
If you're keeping the original be sure to crack test everything or replace.

[911hillclimber]

As the depth of damage gets revealed bit by bit I'm wondering about a 993 on PMO's.
I do not know the block differences though because i want to retain the unique flat fan of this engine and the headers I've made.
anyone have a pic of a bare 993?
I have a parallel thread on Impact bumpers growing, so doubling the info source.

I am most reluctant to spend a lot on this project. It has been nearly intolerable up to this event made worse by my 73T/3.2 only needeing £800 of Kumho tyres to go racing and actually have some fun.

Tedious!

[Matt black70]

I feel for you Graham.
I'll give Derek a call on your behalf, he has a 993 engine he intends fitting in his car.

Matt