I have no specific answers to your second question. I'd imagine if you mill
the block/head you'd be lightening some, but lightening is not the real
purpose for that. However, IIRC you do have to stay with the stock cast iron
block (no aluminum blocks a la drag racing allowed).
On Q1, however, what you describe sounds "normal" to me. One question is,
what caused the engine to blow. I've blown two engines lifetime, and
determined in both cases it was a rod bolt or rod cap that let go. When that
happened it threw the piston up into the head with considerable force,
shattering the piston (which is better than cracking the head! Good that the
piston was able to absorb the majority of the force.)
I'm surprised the rod seemingly survived, but probably it really didn't.
Look close. It's probably bent (even a little and it's toast). The wristpin
does not surprise me at all. That's a tough little piece of metal. In one of
my blown engines there was a silver-dollar size hole in the side of the
block (the old cartwheel dollar, not the Susie or the Sac), but no evidence
of a wristpin anywhere. I figured that as the pin, now free of the piston,
fell, the crank came around and baseballed it out the side. In the other,
the wristpin was in the pan and looking pretty pristine -- but no, I did not
re-use it.
Remember when all that happens, your engine likely was not at idle -- maybe
6000-8000 rpm. Think about it, that means your engine is rotating something
like 100+ times per SECOND! Things are pretty violent in there, and when it
lets go it lets go violently. Parts and pieces are suddenly crashing into
each other and few survive the impact. The piston may take the first hit and
if its aluminum it shatters pretty easily. Total loss is hardly rare, it is
expected. And then all those bits flying around inside the cylinder does the
cylinder walls no good (it can probably be sleeved). If the piston came off
the crank, probably the crank journal is bunged up (that can be welded,
resurfaced and fixed -- if the crank isn't bent or cracked). Everything else
in there from valves to rod bolts gets replaced. I felt lucky on my two
blown engines that the head did not need repair. On one of them, the top of
the flattop piston was jammed into the head intact (everything below the top
ring was gone) and when I pulled it out of the head there was a neat imprint
of the headwork, sparkplug and valves.
No, I'd say the damage you describe is pretty much what would be expected.
To me the surprising thing about a blown engine is that the "BOOM" never
really happens. Rather, if you are alone (as I was both times) it is sudden
silence. The engine's roar is suddenly ceased. First time, when I holed the
block, it was "what's all this smoke? Omigod, it's me!" Second time, when I
did not ventilate the block, it was just silence and the tach at zero.
--Rocky Entriken
----- Original Message -----
From: "andrew stark" <whitedog72@hotmail.com>
To: <fot@autox.team.net>
Sent: Friday, April 12, 2002 5:30 PM
Subject: engine weight/things that go boom
> Two weeks ago I ran a SCCA super school in a Gt-4 EXP. I made the first
> day, but 2/3 of the way through the second day the engine came unglued.
Made
> a big boom! education by fire and all that stuff. Needless to say I did
not
> complete school. In hopes of running the IRP school I am helping the owner
> of the car install a new engine.
> Two things about the engine I am very surprised by are.
> 1: the piston completey exploded taking the cylinder wall with it. There
are
> no pieces of the piston bigger than a quater left. The rod, rist pin and
> valves seem to be relativly ok with just nicks and scraps in them. My
> question on this is. Is this a rare thing to have this kind of total loss
> on piston?
> 2: The blown engine and the new engine appear to have been lightened. It
is
> very obvious that alot of meat has been taken off the block. These two
> engines were so light that I could pick up the long block without a
> struggle. I am not a strong guy so this amased me. While looking at this
the
> wheels started turning in my head. " My Gt-6 is very nose heavy by nature
> because of the brick #$#!house of an engine sitting up front. So my second
> question is can a Triumph engine block be lightened??
> Thanks
> Andy Stark
> 72 EP GT-6
>
>
>
>
> _________________________________________________________________
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