Hello All,
Sounds to me like it could be pre-detonation. Maybe the piston got a
hot spot and preignited the fuel and blamm-o!!!
Daniel 69 2000
> Fred,
> The front of the piston was just blown to pieces, intake port on #3 and rear
> carb throat are coated with tiny little fragments. Looking down the
> cylinder, the wall is scored and already completely rusted out. I don't know
> how to tell if the block can be saved, but it sure looks ugly to me. I'll be
> saving that piston !
> I'll have some pics soon.
>
> Stephan.
>
> > -----Original Message-----
> > From: Fred_Katz@ci.sf.ca.us [mailto:Fred_Katz@ci.sf.ca.us]
> > Sent: Tuesday, October 12, 1999 9:54 AM
> > To: datsun-roadsters@autox.team.net; Sochoux; Stephan
> > Subject: Re: Blown engine
> >
> >
> > Stephan,
> >
> > Wow, bad news! The engine isn't necessarily trashed. It just
> > depends on
> > how much cash you have sitting around! I think you're on the
> > right track
> > - get another runner or engine, as your '69 U20 will take a while to
> > repair. If you tear down the engine, don't throw away the piston as
> > it'll be something everyone else will want to see.
> >
> > When you say vaporized, do you mean "melted" or do you mean
> > fragmented?
> > If it's the front of the piston, that's where the intake valve is, so
> > it's possible that something got pulled in. Maybe one of your rings
> > broke and took the piston top out. That's the only way I
> > could see the
> > hex screw head causing problems, if it got squished and the
> > metal jammed
> > the rings. When I cleaned up my pistons, I found some metal jammed in
> > one of the ring landings, so I know it happens. You should
> > drop the oil
> > pan, and pop out that piston so you can inspect the condition
> > of the #3
> > cylinder. If you didn't get any metal fragments dropping below the
> > piston, and #3 cylinder isn't damaged, it may be possible to
> > re-hone the
> > cylinder and put in a new piston without pulling the engine. But get
> > second opinions on this, as you will be better off going the whole
> > distance by a complete teardown. Let me know what you need as
> > I have the
> > tools.
> >
> > Fred
> >
> > ________________________ Reply Separator __________________________
> > >Subject: Blown engine
> > >Author: "Sochoux; Stephan" <SSochoux@dbc.com>
> > >Date: 10/12/99 7:51 AM
> > >
> > >A little update on my latest "breakdown":
> > >
> > >Pulled the head off last night, front 1/4 of piston #3 is
> > vaporized !
> > >Head looks fine though. Any clues to look for to determine
> > the cause ?
> > >I did notice that the head of the hex screw on the throttle shaft
> > >holding the butterfly (rear carb) was sheared off. Why that would
> > >happen is a mystery by itself, but would such a tiny head
> > screw crumble
> > >a piston if sucked in ?
> > >Anyway, i'm looking to buy a U20 engine or possibly a low windshield
> > >2000 project car (running) while i pull the motor out. I think it's
> > >trashed.
> > >
> > >Thanks-
> > >
> > >Stephan.
> >
> >
>
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