Knurling is very useful to take up a thou or two, ie a very minor
wear deviation from factory specs, and only when everything else
in the bore and on the piston is in perfect order, ie you are not
reboring, just honing. You are in fact slightly expanding a close
to stock aluminum piston to take up a bit of cylinder wear,
(mainly caused BTW by the rings).
Usually, done only on the thrust side, where the contact pressure
is less. Supposedly knurling holds oil better and helps lubricate
that non thrust surface.
Light knurling is a metal deformation process, and like forging
and peening does not necessarily weaken metallurgical
characteristics. Please note, this is only a thou or two, you can
barely feel it - very unlike the knurling you see on a hammer
handle.
Each piston knurled must be clearance matched to its own bore.
You really got to have a good reason to this and then only by a
machinist craftsman who knows what he is doing.
I remanufactured an 18,000 mile Etype engine and did not have to
go oversize by knurling. 10 years ago and still runs like new.
Mike L., P. Eng.
60A,67E,59Bug
----- Original Message -----
From Ulix Goettsch <ulix at u.washington.edu>
To: Spridget List <spridgets@autox.team.net>
Sent: November 6, 2000 10:36 PM
Subject: Sleeving the block on a 1380?
> Thanks to everyone who responded about my piston to bore
clearance.
> Knurling crossed my mind after I posted, but after talking to
Dave Anton at
> APT today, it would require bigger rings to match the bigger
bore and would
> offer less surface area to the bore, making the pistons wear
faster. Does
> anyone have experience with knurling pistons?
>
> Dave also mentioned antifriction coatings that could potentially
be applied
> thick enough. Any opinions?
>
> I also talked to the owner of the LBC shop through whom I had
contracted the
> work. He talked to the machine shop and they say they will fix
the block if
> they indeed made a mistake. So next, I have to tow the car to
the shop to
> have them measure the bore and pistons. They will probably
suggest sleeving
> the block. Is this possible/safe to do on a block that is to be
bored to
> 1380cc? I checked Vizard but found no info. Des Hammill
suggests in his
> book to avoid blocks that have been sleeved in the factory due
to
> manufacturing defects for racing use since the sleeve might
break. I won't
> be racing, but bore flex might stress the sleeves. Also I just
don't know
> if there is enough room for sleeves.
> Will an even thinner wall and a thin sleeve be as strong as the
wall is now?
>
> If sleeves won't work, I would have to find another block and
have the shop
> redo bores, cam brgs, align hone the mains, etc plus potentially
pay for the
> block. That might be a hard sell on my part.
>
> Thanks for any input y'all might have.
> Ulix
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