[Amc-list] Piston Stretch

["Bruce Hevner" <scramblr@xxxxxxxxxxx>]

>I have a piston tech question for you gurus.  I bought a really nice
set of Arias forged pistons from Ebay, for use >in my 304 stroker build.
They were originally built for a 232 0.060" over build, but since there
are 8 of them, I'll >use them in the V8.  Since they are 0.060" for a
3.810" bore, they measure 3.785" roughly in the calipers.  I >calculated
they are this small for a 1.00661 % expansion when heated up, to achieve
to correct bore size.
   
  >So, here is my question . since the bore increases 1.00661%, would
the compression distance also grow >1.006"?  I want to effectively
calculate the final compression ratio and this could be off by 0.011".
Thanks all for >the feedback!

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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://splatter.wps.com/pipermail/amc-list/attachments/20080317/d244c061/attachment.htm 
_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list