sellecting the correct compression or PIN HEIGHT in pistons

grumpyvette

Administrator
Staff member
http://kb-silvolite.com/calc.php?action=piston_comp

http://victorylibrary.com/mopar/rod-tech-c.htm

BBC deck heights are NOMINALLY 9.8" on most blocks and 10.2" on SOME truck blocks
theres also AFTERMARKET 10.6" and 11" deck blocks
most SBC blocks have a 9" deck height, all those blocks tend to have an additional .020-.025 deck height to allow machining the deck to get it 100% square with the crank centerline.

this caculator above might help

just some info
lets say you want to install a 4.25" stroke crank and a 6.135" length rod in a 454 block to build a 489 BBC the deck or compression height is 1.52" like the piston displayed below.

http://kb-silvolite.com/performance.php ... s&P_id=121

now youve got the option of useing a longer 6.385 "connecting rod and a shorter 1.27" deck or compression height piston to build the same basic 489 BBC.

http://kb-silvolite.com/forged.php?acti ... s&P_id=373

OR we can build a 427 BBC with those longer 6.385" rods and these pistons

http://kb-silvolite.com/forged.php?acti ... s&P_id=358

NOTICE THE SAME 1.52 DECK HEIGHT

which you should easily see allows that 1.27 deck height piston with a 6.5" long aftermarket connecting rod.

http://www.scatcrankshafts.com/PDFs/ScatCrank07.pdf

LONGER RODS AND SHORTER PISTONS TEND TO BUILD LIGHTER TOTAL ROTATING ASSEMBLIES
pistontem.jpg

pistontemq.gif

Mahle pistons are designed for specific applications with the alloy that is best suited for that particular application.
but keep in mind the better versions of forged pistons tend to have the advantage in both strength and heat tolerances

......................Piston Alloy Comparison
4032...................................................... 2618
High silicon............................................No silicon
Low expansion........................................expansion
Tighter piston-to-wall clearance................More Piston-to-wall clearance needed
Quiet Operation......................................Noise when cold
Less ductile............................................More ductile
More stable & consistent.........................Higher resistance to detonation
Longer life cycles....................................Shorter life cycles
Harder...................................................Softer
 
keep in mind that maximizing the useable compression ratio builds a good deal more torque than youll get with a significantly lower compression, but to do that both cam timing and the ignition timing curve must be carefully matched to the fuels octane, and burn characteristics
engbal5.gif


http://racingarticles.com/article_racing-10.html

http://www.popularhotrodding.com/tech/0 ... index.html

https://www.engineprofessional.com/EPQ2-2020/mobile/index.html#p=17

http://garage.grumpysperformance.co...s-one-really-over-looked-part.978/#post-79095

http://victorylibrary.com/mopar/cam-tech-c.htm

http://victorylibrary.com/mopar/otto-c.htm

http://www.sdsefi.com/techocta.htm

http://www.sdsefi.com/meltdown.htm
 
Last edited by a moderator:
If your thinking of stroking a 454 big block Chevy with a 4.25" stroker crank to build a 489-496 stroker, theres internally and EXTERNALLY balanced crank assemblies, the longer 6.385" rods and INTERNAL BALANCING is the preferred route if you can, because it allows larger counter weights on the crank to clear the piston skirts, larger counter weights that allow less internal stress and vibration and internal balancing.

yes it possible to use the standard 6.135" rods the 454 cam with but thier fairly short at 6.135" and the correct size counterweights for internal balancing clear the piston skirts far better with the slightly longer 6.385"rod length

keep in mind stock 3/8" rod bolts are pitifull compared to 7/16" ARP rods and aftermarket rods is generally a far stronger option.
stock rods
http://kb-silvolite.com/forged.php?acti ... dLen=6.135

6.385" rods

http://kb-silvolite.com/forged.php?acti ... dLen=6.385

read

viewtopic.php?f=53&t=942

http://www.adperformance.com/index.php? ... page=index

http://www.performance-auto-parts.com/s ... forged.php

forged components are generally stronger
(IE will take abuse longer and at greater stress levels) and forged pistons are slightly more heat resistant than hyper eutectic or cast
as a general rule if your going to exceed 100hp shot of nitrous or have the rotating assembly spin at near 4000 feet per minute in piston speed forged components tend to be a good investment

viewtopic.php?f=53&t=110&hilit=4032

viewtopic.php?f=53&t=343&p=1170&hilit=redline#p1170

viewtopic.php?f=53&t=204&p=239#p239
 
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