Re: [Amc-list] Piston Stretch

[Greg Taylor <amundaza@xxxxxxxxx>]

Bruce Hevner <scramblr@xxxxxxxxxxx> wrote:  Good question!! Got you thinking!!
FIRST,, I would recommend you call Arias. I have dealt with them before
and they have always been very receptive to questions and willing to
help. BEAUTIFUL products!!!
It depends on the TYPE of material they are made from. Low or high
silicone, and the design of the skirt. MOST (I HIGHLY recommend you call
them) High Silicone pistons are designed to be run "tight" close to
stock clearance. MOST low Silicone are meant to be run "loose" because
they expand more.
Pistons do NOT expand uniformly when in use. TRW USED to have some nice
charts showing the different temperatures at different points of a
running piston. They used them as a selling point for their forged
pistons. Wish I still had those things! Anyway the temp on the top of
the piston is MUCH higher than the skirt. AND they don't grow uniformly
so it would be kinda hard to tell how much the crown (top) will expand.
If it's quench you're worried about it doesn't have to be exact of
course the closer the better but better to error on the loose side!!
Pistons touching the head is NOT a good thing! 
I shoot for a MINIMUM of .038 on street under 5500 RPM motors. On race
motors 7500 RPM shoot for a minimum of .042 (steel rods). 
The late great Smokey Unick did a lot of research on quench and said
that anywhere between .040 and .060 is OK but over .060 you start losing
the effect. 
If you're interested in combustion chambers and their effect on power
(like I am!) check DIS guy out,,,
http://somender-singh.com/component/option,com_frontpage/Itemid,1/
But HEY,,, that's just ME!
Bruce Hevner

  Hi Bruce,
  Thanks for the feedback on piston stretch/expansion.  With my current setup, the piston?s will be 0.030? in the hole and make about 10:1 compression with the Ebay advertised 1.595? compression distance.  I?m waiting to hear back from the seller if this was Arias? value for height or not ... and will be measuring the with Calipers.
   
  These are older Arias pistons that were forged by ALCOA and include the skirt clearance spec card from Arias.  They are old enough that Arias doesn?t have records on file for the Job #.
   
  As for Somender Singh and his ?Groovy Ideas? ? I am already planning to incorporate those into my AMC heads.  Check out this link ? http://speedtalk.com/forum/viewtopic.php?t=4069 ? I have been in touch with one of the head builders there and he has given me good feedback on where to place the single groove for AMC heads.  He typically runs 10:1 compression with 87 octane on grooved heads in various motors.  He has also set up 12:1 engines to run on 92 octane with grooves, but stated that it took some testing to get them right (for 92 octane).  Another site he recommended checking out is http://forums.turbobricks.com/showthread.php?t=66779 
    
 



Sincerely,
Greg Taylor :)  <><

And the testimony is this, that God has given us eternal life, and this life is in His Son. He who has the Son has the life; he who does not have the Son of God does not have the life.  - 1 John 5:11-12
       
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