couple of generic engine questions

[jdbubb at ix.netcom.com (Dan Bubb)]

Oh! This will be fun!
Throwing a rod is when the rod either becomes disconnected from the crankshaft or the piston or the
connecting rod itself breaks.
Usually, it becomes disconnected from the crankshaft via the rod bolts or bearing cap breaking.
I only say this since the post mortem pictures generally show the piston and remainder of the rod
still attached.

Two reasons for failure (I can hear Larry chiming in his .02 as I type!):
Excess mechanical stress from overrevving the engine or just plain component failure. The connecting
rod bolt is the most highly stressed bolt in an engine. Reusing an old stretch bolt or incorrect
torquing of the bolt if you intend to hit redline often could be reasons for mechanical failure.
Second is lubrication failure. There is only a thou or two clearance and if you loose oil pressure
while running the engine hard there can be metal to metal contact, extreme heat build up and
seizure. This can rip the big end right off the rest of the rod!
Of course, the most dramatic aspect of "throwing a rod" can be "ventilating the crankcase" where the
parts manage to come right thru the side of the block. Probably not much difference in the cost to
repair, but a lot messier and a lot more cool stuff to show your friends ;^)
Remember the pictures of the Honda engine on Vortex with multiple ventilations? The guy downshifted
from 5th to 2nd while doing over 100mph. One piston ended up as an aluminum ball! He had the coolest
best pictures of all!
Dan

----- Original Message -----
From: "Mike Smith" <smithma7@yahoo.com>
To: "car" <scirocco-l@scirocco.org>
Sent: Thursday, July 29, 2004 3:09 PM
Subject: couple of generic engine questions


> Greetings collective!
>
> 1)  What is "throwing a rod"? (as in "You've thrown a rod")
>
> 2)  How does it happen and/or what causes it?
>
> TIA,
> Mike
> '86 red 16v (Red 5)
>
> ps.  Not my car, just questions.
>
>
> word (w?rd)
> interj. Slang. Used to express approval or an affirmative response to something. Sometimes used
with up. Source
>
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