Forged or ... not ?
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
i have a forged set of TRW's (if i remember correctly) and they are a bit noisy for about 3-4 mins. on a cold winter morning; once the engine warms up a bit they're quiet.
and i wouldn't really even register it as a complaint as far as i'm concerned.
and i wouldn't really even register it as a complaint as far as i'm concerned.
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
I'm not disagreeing, but asking out of my own ignorance. When you gonna get that ? I'd be inclined to think one's motor has some serious issues if there were detonation occurring under full retard. I'd not expect detonation under full retard. enlighten me a little ? thanks 
The mahle power packs (forged)) are pretty quiet in my build
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Meps
biggie in forged vs cast is what 'engineeer types' refer to as MEPS (mean effective piston speed)...MEPS is itself a misleading 'reference number' as the piston speed is ZERO at each end of its stroke and 'mean' (aka averaged) speed is a poor substitute for the real gremlin at work here, namely 'acceleration'...but longer engine strokes would require a higher average piston speed anyway, and thus giving a higher 'mean' speed 'number' for reference use, and easier to calculate than 'A'.
'acceleration' of the piston 'multiplies' the weight of the piston, and has resulted in many,many cases of actually 'pulling' the wrist pin out from the piston at high engine speed (rpm), resulting in total engine destruction...'cast' pistons will fail at lower engine speed than forgings, found (the hard way) to be about 5800 rpm with a 3.5'' stroke for the cast type.
hope this makes sense, tryin to put years of theory into a few words is not ez
'acceleration' of the piston 'multiplies' the weight of the piston, and has resulted in many,many cases of actually 'pulling' the wrist pin out from the piston at high engine speed (rpm), resulting in total engine destruction...'cast' pistons will fail at lower engine speed than forgings, found (the hard way) to be about 5800 rpm with a 3.5'' stroke for the cast type.
hope this makes sense, tryin to put years of theory into a few words is not ez
Race Director
Joined: Feb 2004
Posts: 12,518
Likes: 19
biggie in forged vs cast is what 'engineeer types' refer to as MEPS (mean effective piston speed)...MEPS is itself a misleading 'reference number' as the piston speed is ZERO at each end of its stroke and 'mean' (aka averaged) speed is a poor substitute for the real gremlin at work here, namely 'acceleration'...but longer engine strokes would require a higher average piston speed anyway, and thus giving a higher 'mean' speed 'number' for reference use, and easier to calculate than 'A'.
'acceleration' of the piston 'multiplies' the weight of the piston, and has resulted in many,many cases of actually 'pulling' the wrist pin out from the piston at high engine speed (rpm), resulting in total engine destruction...'cast' pistons will fail at lower engine speed than forgings, found (the hard way) to be about 5800 rpm with a 3.5'' stroke for the cast type.
hope this makes sense, tryin to put years of theory into a few words is not ez
'acceleration' of the piston 'multiplies' the weight of the piston, and has resulted in many,many cases of actually 'pulling' the wrist pin out from the piston at high engine speed (rpm), resulting in total engine destruction...'cast' pistons will fail at lower engine speed than forgings, found (the hard way) to be about 5800 rpm with a 3.5'' stroke for the cast type.
hope this makes sense, tryin to put years of theory into a few words is not ez
Safety Car
Joined: Jul 2008
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From: Made In America
St. Jude Donor '10-'11
The 85s pistons are forged because they carried them over from the C3s. L98s suck. Lt1s are a smidge better IIRC?
Safety Car
Joined: Jul 2008
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From: Made In America
St. Jude Donor '10-'11
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
next time, if there is a next time, its gonna be a 427 out of the factory. ahh F it, why not a top fuelie dragster to go to work in
torque is king, the rest is numbers and empty boasting.
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Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
btw, mfr reccomended skirt clearance for my forged h-u pistons is .0015'' MIN, have run these back/day at .006'' with no prob other than slight noise (piston slap) at cold start...a 'dummy' that 'redlines' this when cold could be sorry.
Last edited by redrose; May 3, 2009 at 12:33 PM.
Race Director
Joined: May 2003
Posts: 10,749
Likes: 41
please don't be envious of my engine; there's nothing to be impressed with. cubes -- that's where the real deal is and that's where i screwed up. my bad, my lack of experience.
next time, if there is a next time, its gonna be a 427 out of the factory. ahh F it, why not a top fuelie dragster to go to work in
torque is king, the rest is numbers and empty boasting.
next time, if there is a next time, its gonna be a 427 out of the factory. ahh F it, why not a top fuelie dragster to go to work in
torque is king, the rest is numbers and empty boasting.
did you sell that thing yet?
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
It's a matter of the expansion rate of the material the piston is made out of. Forged pistons expand more, so call for greater piston to wall clearance. So what you hear is piston slap that goes away once the piston heats up, expands and tightens the piston to wall.
GM tried to address complaints about that noise over the years in an attempt to keep customers 'happy campers'. GM seems to be quick to jump on the band-wagon of a new part when it seems to save them a few pennies. Many times this results in the new part being less able to handle high stresses.
I've also always hated GM's production tolerences too. Widening the tolerences saves them money, but results in a less than desirable engine build. It's the main reason I have never recommended a crate engine to anyone. Everything will arrive all clean and shiny, but you never REALLY know what you're getting.
Just my views.
Jake
West Point ROCKS!