Help me solve an arguement...
#870852
12/04/10 03:56 AM
12/04/10 03:56 AM
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Joined: Feb 2005
Posts: 5,207
Menomonee Falls
DemonDust
OP
master
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OP
master
Joined: Feb 2005
Posts: 5,207
Menomonee Falls
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My buddy and I are arguing about a very simple subject I think... I could be wrong. I'm trying to convince him that on a steel block, aluminum headed engine, as it warms up the lash loosens up. He tells me it gets tighter. Please tell me I'm right 
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Re: Help me solve an arguement...
[Re: DemonDust]
#870853
12/04/10 03:56 AM
12/04/10 03:56 AM
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Joined: Feb 2006
Posts: 2,379
MD
Kevins493
top fuel
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top fuel
Joined: Feb 2006
Posts: 2,379
MD
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you are correct. Easiest argument to make is the aluminum heads expand at a much higher rate (vs temp) than the steel or moly pushrods. I believe cast iron does as well. just not looking it up now.  so basically you are making the pushrod seem "shorter" in relation to the distance between the lifter and the rocker (or technically adjuster) so you have more clearance.
Last edited by Kevins493; 12/04/10 03:59 AM.
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Re: Help me solve an arguement...
[Re: DemonDust]
#870857
12/04/10 04:10 AM
12/04/10 04:10 AM
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Joined: Aug 2003
Posts: 43,157
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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Your correct, aluminum expands eight times more than steel and cast iron when heated to the same temperatures as each other  Google aluminum expansion rates, one of my old Crane Cam catalogs says to set the lash .002 loose when setting the valves on a cold cast iron motor, set them .006 tighter cold with aluminum heads on a cast iron block and set them .012 tighter cold on a aluminum block with aluminum heads. I found that information to be accurate on the first all aluminum street Hemi motor I built and on many other mtors since with iron blocks and aluminum heads  you do want to check each motor to make sure those settings is what that motor needs and wants 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Help me solve an arguement...
[Re: Cab_Burge]
#870858
12/04/10 11:04 AM
12/04/10 11:04 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Yeah I use .006 as the cold/hot difference.. then I also run my lash .010 tighter than spec calls for but still with the .006 difference 
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Re: Help me solve an arguement...
[Re: MR_P_BODY]
#870859
12/04/10 11:17 AM
12/04/10 11:17 AM
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Joined: May 2005
Posts: 6,446
NJ-USA
HPMike
master
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master
Joined: May 2005
Posts: 6,446
NJ-USA
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Even though it's a pain at times, I always make a point of checking the lash hot. That's what the engine actually sees, so it makes the most sense. Eliminates the guesswork. Minor lash variations can make some significant horsepower swings(both ways) on some engines, so it's always a good idea to have this ironed out.  MB
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Re: Help me solve an arguement...
[Re: MR_P_BODY]
#870863
12/04/10 01:51 PM
12/04/10 01:51 PM
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Joined: Jan 2007
Posts: 3,695
nc
emarine01
master
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master
Joined: Jan 2007
Posts: 3,695
nc
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Quote:
Yeah I use .006 as the cold/hot difference.. then I
also run my lash .010 tighter than spec calls for
but still with the .006 difference
I guess you dont like roller cam valve chatter 
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Re: Help me solve an arguement...
[Re: emarine01]
#870864
12/04/10 01:58 PM
12/04/10 01:58 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
Yeah I use .006 as the cold/hot difference.. then I
also run my lash .010 tighter than spec calls for
but still with the .006 difference
I guess you dont like roller cam valve chatter
No its not that... I need all the lift I can get,
one of these days when I get a few bucks I'll have
it reground for another .100 lift(I went wimpy the
first time around)
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The way I explain it is that since the aluminum expands so much, it's actually pulling the rocker arms away from the block...... 