Engine Damage

[Superman]

Relax, my engine is fine. But I was wondering, if one of my engine's valves were to lose it's head, would the crank be damaged? Certainly a piston and head would take a beating, and a cylinder possibly. But would this damage the crank?

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'83 SC

[Early_S_Man]

Are we computing actuarial tables for 911SC engines, given all of the possible ends to a certain set of possible constraints or variations of one broken Dilivar stud and the propogation of engine damage?

Just wondering?

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[Ted Stringer]

I would say probably yes. It will endure the shock of the piston tring to compress a hard object. I would at least have it checked with an x-ray before using it again

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Ted Stringer
nuke3@juno.com
'84 911 Targa aka pocketrocket

[dtw]

Lots of fascinating things can happen when valves drop, float, break, etc. The 911 engines I have seen- the cranks have all survived since the rod bent first. The crank can take other more subtle collateral damage. Shrapnel gets created when you turn your combustion chamber into a 6000 rpm machine shop- these bits like to find their way to the bottom end and wreak havoc. Either small bits get sucked into the oil pump, destroying it, or smaller ones get lodged in oil galleries. Bigger pieces get lodged in really cool places and make pretty sculpture out of expensive German engine pieces. Worst case I've seen was an 11k mechanical overrev- valve floated, piston ate itself, entire piston dropped into bottom end (it was just a ball of slag at that point) and holed the oil pump, took chunks out of the crank, and beat the snot out of the case. Nonetheless, the crank passed all machine shop tests and cleaned up nicely. 911 cranks- especially the venerable 70.4mm- are hard to kill.

I guess what I'm trying to say is best summarized by "Forrest" Ellison, local 911 engine wizard:

"Valve drops are like a box of chocolates- you never know what you're gonna get..."

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Dave
'72 911T to '73 RSR Replica Project

[john walker's workshop]

sometimes, it's just about the only thing that survives a dropped valve. worst case scenario, the case, all the pistons and cylinders, heads, oil pump, intermediate shaft, all get taken out. all because the guides were sloppy, or that tensioner failure last year that slightly stressed a valve as it hit a piston.

[Superman]

Very amusing. I've got to admit (and most of you should too) that seeing the kinds of mechanical carnage that can happen in engines gives me a kind of macabre thrill....as long as it is not MY engine. I will be tearing my engine down soon, and I will be pleased with the extra security of dealing with any valve issues I have. On the other hand, I plan to autocross the car tomorrow, so as to keep my Rambo/Neanderthal image alive, at least in terms of my motoring philosophy. I'm estimating that tomorrow will not present me with an opportunity to engage in the Boulean failure-forecasting statistics that were so popular following the Challenger disaster.

I learned from John that valve head dances can spread the carnage far and wide. But I am also hearing that these cranks are so tough that they can survive, even when nothing else does.

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'83 SC

[911pcars]

Why are you so enamored of just your crankshaft? Surely the lowly rocker arms should feel just as wanted.

[dtw]

Hmm..at $35 each new, these just don't rate the same concern!

-d

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Dave
'72 911T to '73 RSR Replica Project

[Superman]

Indeed. The crankshaft is the most valuable single piece of metal on my car, hands down. I'm a bit of a risk taker, but I like to show some good sense occasionally.

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'83 SC

[BRAINIAC]

Glad to hear you're going to auto-X that thing tomorrow, Superman. See you there! (I'll bring some kitty-litter just in case)

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet