Pistons R Pistons,,or ARE they?

["Bruce Hevner" <scramblr@xxxxxxxxxxxxx>]

>I'm not positive that Silvolite doesn't still make the Badger pistons.
There was a big >merge/close-down of piston manufacturers 6-10 years ago.
The bad batch could have been rushed >during a merger, or rather made
shortly after manufacturing facilities were changed. At any rate, >the
problem seems to have been fixed. 

I think you are right about that. I never sold Badger direct but I DID sell
Silvolite and Ertle (sold under about 4 different brand names, Ohio, Nylen,
etc). They way I understood it back then  the problem was (and they DID have
a problem! not just AMC pistons) at least partially due to the
buyout/reorganization. In the shop where I work now we see Badger pistons
all the time. I have not seen any problems with them in a LONG time. Not
saying there aren't any, but I am not seeing any with the stuff they sell
now. We don't do a LOT of AMC work, mostly 304 Jeeps, some 360 too. Haven't
seen any of them having problems.

>When badger took the manufacturing of the pistons over again, they used
"struts" to reinforce the >piston skirts to control expansion and cracking.
This is a common practice with many production >car engine manufacturers as
well. The struts are basically steel(I believe) plates. If you get a >set of
Badgers without the struts you "could" have a set manufactured by silvolite
that "may" have >a problem with!

Most ALL OE cast pistons will have steel struts in them. Problem is many
times you won't be able to see them because they will be completely covered
in the casting. So just because you can't SEE the struts does not mean they
aren't there.

>You don't want forged pistons unless you're building a race engine. They
require more clearance >and are therefore noisy (like a warmed up diesel)
until the engine warms up.

Not necessarily, TRW (now Federal Mogoul) has made stock type (along with
high performance) forged pistons for YEARS! The difference is in the design
of the oil drain back of the oil ring groove. In the high performance piston
the oil drain back is most often done with HOLES drilled in the slot. This
makes the piston skirt MUCH stronger but also allows the heat from the top
of the piston to travel down to the skirt much more rapidly. One of the main
reasons for more clearance. On the stock type forged piston there is a SLOT
cut in the oil ring groove for oil drain back. This slot effectively
prevents the heat from the top of the piston from going directly to the
skirt. The slot allows this type piston to run OE type clearance.
  The stock type FORGED TRW piston uses say .0015 clearance for street use
(4" bore). The same piston can be used for light high performance by
increasing the clearance to about .003. The High performance type FORGED TRW
piston needs about .005 (or a little more) clearance. The stock type piston
will not be noisy; the high performance WILL be noisy till it warms up.

Forged pistons are not necessarily better than cast depending on the usage.
It has a lot to due with the stress the piston will take. The bigger the
bore the higher the stress (among other things). Take motorcycles, they
(usually) have pretty small bores (2-3"). These things use cast pistons and
twist to 12 or 14 THOUSAND RPM all the time. But look at the bore size.

I have also used Hypereutectic pistons with reasonable success. Lots of OE
TURBO engines use Hyper pistons. They REALLY resist scuffing compared to
stock pistons. But they are CAST pistons so there are some limitations. Cast
pistons as a rule are lighter (and MUCH cheaper to make) than forged
pistons. Main thing that kills cast pistons on the big bore sizes is RPM. I
tried to keep all my cast piston 4" bore motors under 6500 or so RPM. Seemed
to do OK there. Above 7000 and you're on your own. Here's a good comparison
from Silvolite,,,
http://www.kb-silvolite.com/article.php?action=read&A_id=5

I'm sure others will have their own take on this topic. I base mine on over
35 years of engine rebuilding in which I saw THOUSANDS of engines of all
types taken apart and rebuilt. And the fact that I was a factory direct
dealer for Silvolite and Ertle engine parts for about 10 years.
But hey,,,,,, that's just me!!
Bruce Hevner