Subject: [alfa] Piston Slap

[RonHorowitz <RonHorowitz@xxxxxxxxxxxxxx>]

>Subject: [alfa] Piston Slap

>I have a '87 Spider Veloce which has been diagnosed as having piston slap
in
>the #1 cylinder.

Without hearing it myself, I don't know for sure, but I sort of doubt it.

>makes a tapping noise which goes away when the #1
>plug is removed.

I'd say piston slap if the piston rattles when the engine is cold, but
quiets down as the motor warms up. Forgings do that. Hypereutectics do it
to a lesser degree, or if you overbored the cylinder too much. Borgo
pistons are castings, with steel struts cast in, and they are typically
supplied with new liners. Also, whoever built the motor would have checked
clearances before assembly (I hope....) Piston slap just seems unlikely to
me. (I could be wrong!)

Unless the guy that built your motor re-ringed the old pistons and honed
the old liners, what you describe strikes me more like excessive clearance
at the pin, or possibly the big end, though that seems unlikely from what
you description. Does it rattle more or less when under load (or when you
lift)? Does it rattle more at a certain RPM or all the time? Rattle more
cold or hot?

>My opinion is that the liner is abnormally worn,

Unless you've been running the engine without an air filter, or unless
someone honed the bejeezus out of the old liner, I'd say this is
particularly unlikely for a motor with only 25k.

>
>Also, there is no smoke at all from the exhaust.

Just means the rings / bores are good. Doesn't have anything to say about
pin clearance (or even piston clearance for that matter.)

>My question is this: Is
>there any potential for catastrophic failure if I just go ahead and drive
it
>and ignore the noise?

If it's _just_ a little too much pin clearance, you could _probably_ drive
on it for many miles (if you can stand the racket.) On the other hand, if
the pin clearance is indicative of an oiling problem, I suppose it might
give trouble.

>Also, has any one ever heard of a problem like this on
>such a low milage engine?

Not on an Alfa specifically, but sure. Wrong clearances on build up,
plugged up oil jet on a rod, whatever.

Good luck.
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