Re: Alu rod question
[Re: Dodgem]
#447185
08/23/09 04:36 PM
08/23/09 04:36 PM
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Joined: Jan 2003
Posts: 4,448 Phoenix, AZ
MoparBilly
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Phoenix, AZ
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Umm....technically...the rod doesn't stretch when it's "Static"!!! I never worried about all that "stretch" or growth" stuff with my BME aluminum rods, until I had it apart after 350 passes and saw shiney spots on my heads, and the pistons...figured .054 clearance was enuff, and it almost was...
"Livin' in a powder keg and givin' off sparks"
4 Street cars, 5 Race engines
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Re: Alu rod question
[Re: MoparBilly]
#447186
08/23/09 05:22 PM
08/23/09 05:22 PM
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Joined: Aug 2003
Posts: 43,230 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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Quote:
Umm....technically...the rod doesn't stretch when it's "Static"!!! I never worried about all that "stretch" or growth" stuff with my BME aluminum rods, until I had it apart after 350 passes and saw shiney spots on my heads, and the pistons...figured .054 clearance was enuff, and it almost was...
Come on Billy, BME says .055 minimum, not .054 Just kidding I think it is real important to write down the deck or dome hieght and check it after running them every 200 or more runs, once they start to stretch it is probally a good time to replace them
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Alu rod question
[Re: MoparBilly]
#447187
08/23/09 07:58 PM
08/23/09 07:58 PM
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Joined: Jan 2007
Posts: 3,695 nc
emarine01
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Quote:
Umm....technically...the rod doesn't stretch when it's "Static"!!! I never worried about all that "stretch" or growth" stuff with my BME aluminum rods, until I had it apart after 350 passes and saw shiney spots on my heads, and the pistons...figured .054 clearance was enuff, and it almost was...
Technically it does when its hot, but if the word static is twistin your panties we can change to mechanical compression and back to the point which you kinda answered in a backassward way, I am guessin you were running a .040 head gasket and you had some form of interference @ .054 than .019 was the rod gain ,<.035 min for steel rod> I can add that to my static compression math and come up with a more realistic number, thankx
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Re: Alu rod question
[Re: emarine01]
#447188
08/23/09 08:37 PM
08/23/09 08:37 PM
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Joined: Nov 2004
Posts: 4,330 Lynchburg, VA
Leon441
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With my GRP rods I run .035" clearance. You shouldn't have stretch during compression stroke. But, you probably do when the valves are open.
Leon
Career best 8.02 @ 169 at 3050# and 10" tires small block power.
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Re: Alu rod question
[Re: dvw]
#447191
08/24/09 09:50 AM
08/24/09 09:50 AM
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Joined: Jan 2003
Posts: 4,448 Phoenix, AZ
MoparBilly
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Ummm...technically Doug, Rod stretch would be calculated as less deck height...right? My head is starting to hurt.
"Livin' in a powder keg and givin' off sparks"
4 Street cars, 5 Race engines
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Re: Alu rod question
[Re: MoparBilly]
#447192
08/24/09 03:56 PM
08/24/09 03:56 PM
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Joined: Jan 2007
Posts: 3,695 nc
emarine01
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The BME spec for piston to head is .060 , around .025 more than a steel rod engine, when doin engine math if you use the .060 figure you are shorting the compression ratio quite a bit, So what I was asking was what was a good figure to use for engine math that was closer to actual ratio after heating the rod ,stretch or what ever you wan to call it , since Alu grows, swelles stretches or what ever more than steel if you had a real number you can figure the ratio closer, Take Bills engine , he had piston to head interference at .054 so we now know in a running engine with a alu rod the .054 clearance is no longer there , thats why you got the shiny spots so if most engine math is done using .035 or .040 piston to head math a Alu rod engine should figure a lower than .060 number, now my head hurts also
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Re: Alu rod question
[Re: emarine01]
#447193
08/24/09 04:04 PM
08/24/09 04:04 PM
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Anonymous
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Anonymous
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for te sake of figuring your actual static compression ratio,(on a warm engine) just use .015 shorter deck height in your equation.
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Re: Alu rod question
[Re: MoparBilly]
#447195
08/24/09 08:46 PM
08/24/09 08:46 PM
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Joined: Mar 2006
Posts: 9,858 MI, usa
dvw
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Quote:
Ummm...technically Doug, Rod stretch would be calculated as less deck height...right? My head is starting to hurt.
I agree. I was thinking the height of the piston would be calculated at a taller figure to compensate for the rod being longer when warm. I used the term deck hieght incorectly. Doug
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