[AMC-list] 360 Pistons

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Hi Bruce,

I agree, hyper pistons are more affordable than forged but I think the problem is, there are so many cast versions out there for the 360 that the market probably wouldn't warrant a mid grade piston for AMC.  One reason I say that is I don't think there is the same benefits in regards to skirt gulling in an AMC block as there is in lets say a Chevy engine.  SBC engines were prone to excessive cylinder wear and would regularly need to be bored even in low mile engines.  One know benefit of our blocks over Chevy's is the high nickel content.  Unless an engine was rebuilt with improper piston to wall clearance, they typically wear well in this area.  The longer skirt type pistons did have a tendency to break in the skirt area but most have gone to a shorter skirt in recent years.  I doubt the majority of users would see an issue with cylinder wear especially in cars that don't see the kind of mileage they did new.  I have taken apart lower
 compression AMC blocks with 100K on them that had very little wear and a lot of times could either just be honed or go .010 over to clean up.  When you consider this, most applications were a hypereutectic piston would be a fine choice, a cast piston would most likely also fit the bill.  This is a hard call for a lower compression engine.

I can get with my piston supplier to see if there are any alternative for this but my fear is like with a lot of items people say they would buy if they were available, the activity over cast would not be there to warrant the investment.  

Like I said in my previous post, I feel most guys are looking for that low end grunt torque out of their 360 and smaller engines.  That grunt power really comes from higher cylinder pressures which is the real weak point of cast and hyper pistons.  They tend to break when you have more heat/higher compression or cylinder pressure even at rpms below 6 grand.

One other thing with KB pistons.  They use a Chevy pin diameter in the 401 pistons they make.  This meant you had to bush your rods for that size which brought the cost up a fair amount.  With that, the difference is not as big in price and makes you wonder if it is worth it verses forged.

I htink you have some good arguments for them and might be better to see if one of the cast piston makers would be willing to change their fomula for the pistons they already make to a higher silicone content type piston.

Just my thoughts,

Nick 
 Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends 

Message: 6
Date: Sun, 21 Feb 2010 12:25:58 -0500
From: "Bruce Hevner" <scramblr@xxxxxxxxxxx>
To: <amc-list@xxxxxxxxxxxx>
Subject: [AMC-list] 360 pistons
Message-ID: <000001cab31a$ef45efa0$cdd1cee0$@charter.net>
Content-Type: text/plain; charset="us-ascii"
>I know a lot of you are looking for?cheap alternatives for 360s but one
thing to keep in mind is to build the low end torque most are looking for
out?of a 360, you need higher cylinder pressure.? The cheaper style cast or
>even hypereutectic pistons (hypereutectic pistons are just a?cast piston
with?a higher silicone content) are?them?vulnerable to breaking under these
conditions.? Now if?are looking for a low compression pistons?and a >cam
that?has doesn't create a of? pressure, you are ok but you are also not
going?to get a lot of power?out of it either.? There?are pistons out there
for?most of the AMC?Gen II and III engines in both cast and forged.? >Not
sure why there is a such a big fuss for a piston that is only slightly
better than a stock cast piston.? I am not saying?we shouldn't try to get
these, just that I don't see the huge need.? There are already a few brands
of >cast?pistons for the 360.? I?make?forged pistons for
>them so really both performance areas are fairly well covered.??

I'll have to disagree with ya on this one Nick. First there are different
"grades" of hyper pistons. You are right that hyper pistons are cast pistons
and as such are susceptible to the same limitations that stock cast are,
mostly RPM, HOWEVER they ARE better in several regards. First (and most
important IMHO) is the resistance to skirt galling. There are quite a few OE
Manuf that use Hyper pistons as an upgrade for their turbo motors so
(properly designed and used) they WILL stand up to heavy duty usage. 
I used to do a lot of circle track 2.6 Mitsubishi motors. These things have
a long stroke and are pretty hard on piston skirts, when I would disassemble
them for a "freshen up" the skirts looked pretty bad. One thing I noticed
was the Turbo version of these engines used a Hyper piston and the skirts
had VERY little wear. I couldn't use the turbo version in the circle track
motors because of the deep dish.
I found a manufacturer (now long gone unfortunately) who was making a Hyper
version of the piston which only had a very small dish which allowed use of
the early small chamber head without jacking the compression way up. I could
cut the top of the piston flat removing the dish and lightening the piston
as well. This proved to be the answer and we never had any piston "scuffing"
problems again.
It also makes the ring lands harder which helps prolong ring life. 
Adding Hyper alloy to a piston normally doesn't add a lot to the price.
Nowhere NEAR what forged one's cost.
Then you have the KB line. These are heat treated which does add to their
strength but also adds to the cost. I have used KB pistons with good success
in Toyota and Chebbys as long as they are operated within their limits. I
have even used them in race motors turning 6800 and not had any problems.
As long as you're turning LESS than 6,000 RPM (and most street AMC motors
especially with a hydraulic cam will not see more than 5800) you're BETTER
off with a hyper piston in a NON-POWER ADDED (nitrous or blown) engine!!
The reason for the "big fuss" is COST!!!!
A Hyper piston should come in at about HALF of what your forged pistons are
and would be a great alternate for motors built for the street.
Right now there is NO in between choice from cast stock to forged. That's a
BIG jump for most street engines. If Hypers could come in at $350 that would
save enough to cover the cost of a cam kit. 

As to WHY Silvolite refuses to offer them (even after TELLING me they might)
I don't know. That fellow TOLD me they would NOT have to make a new mold
(that was their excuse last year) and that "it doesn't look like it would
take much to make them" face to face. How can you possibly gauge sales on an
item you aren't making or even promoting??
I wish to hell I could come up with a piston company that would LISTEN to
their customers' requests instead of DICTATING to them. Far cry from the old
days when a rep would visit your shop every couple of months just to see how
things were going and to get feedback, and when you could CALL them and
actually get to TALK to an engineer.
Rant off,,,,,,
But HEY,,, that's just ME!!
Bruce Hevner 

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