Re: Positive vs. negative piston deck height
[Re: Plumcrazyracing]
#173183
12/23/08 01:40 AM
12/23/08 01:40 AM
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Joined: Aug 2003
Posts: 43,317 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,317
Bend,OR USA
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all domes are usually above the top of the deck, the 1970 440 6 paks where .005 above and the early HP 340 (Pre 1972) called for a positive deck hieght also. The last legal 340 stocker I built had the pistons around .030 above, if I'm remembering the blueprint spec on the piston deck hieghts correctly
Last edited by Cab_Burge; 12/23/08 02:07 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Positive vs. negative piston deck height
[Re: Plumcrazyracing]
#173184
12/23/08 01:49 AM
12/23/08 01:49 AM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
Just got a call from my machine shop and learned that i needed take more off the block than anticipated. Pistons are now going to be about .008 out of the hole. I figure i will run a cometic compressed at about .051 to give a quench of .043. Any opinions as to having a positive deck hieght like this?
At that positive deck height .008 I wouldnt be concerned about a thing/nothing mike
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Re: Positive vs. negative piston deck height
[Re: JUST_N_TIME]
#173189
12/23/08 09:20 PM
12/23/08 09:20 PM
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Joined: Sep 2004
Posts: 1,828 houston texas
gremlinsteve
top fuel
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top fuel
Joined: Sep 2004
Posts: 1,828
houston texas
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heck..late model 6.1 3g hemis are 15 out of the hole new. the 5.7 is less...like 5
steve
if You Like Gremlinsteve. Gremlinsteve Likes You.
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Re: Positive vs. negative piston deck height
[Re: JUST_N_TIME]
#173190
12/23/08 09:55 PM
12/23/08 09:55 PM
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Joined: Dec 2008
Posts: 184 Central Coast
Plumcrazyracing
OP
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OP
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Joined: Dec 2008
Posts: 184
Central Coast
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Closed chamber Indy's. .620 lift solid roller on my 493 stroked 440
Last edited by Plumcrazyracing; 12/23/08 10:00 PM.
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Re: Positive vs. negative piston deck height
[Re: Plumcrazyracing]
#173191
12/23/08 10:07 PM
12/23/08 10:07 PM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
Closed chamber Indy's. .620 lift solid roller on my 493 stroked 440
In that case that with that .008 positive piston deck height will cause you a whole heap of trouble.
Plum I , think that open vs closed question was directed a jburch. Plum you will be fine with a closed chamber, jburchs head if its closed is on the tight side. mike
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Re: Positive vs. negative piston deck height
[Re: BobR]
#173197
12/25/08 10:27 AM
12/25/08 10:27 AM
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Joined: Sep 2003
Posts: 1,397 Toronto Ontario, Can
Glen440
pro stock
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pro stock
Joined: Sep 2003
Posts: 1,397
Toronto Ontario, Can
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My 511 was originally .023 above deck. My 400 block was not close to square. Every piston was a different height till I had the machine shop square it. I fixed it with a .062 head gasket.
My custom pistons that are in it now have .025 less pin height to put them -.002.
87 dakota 6.1 hemi
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Re: Positive vs. negative piston deck height
[Re: patrick]
#173203
12/28/08 12:29 AM
12/28/08 12:29 AM
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Joined: Feb 2004
Posts: 4,501 Gainesville,FL
goldmember
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master
Joined: Feb 2004
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Gainesville,FL
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Alot of good points,most don't add up to 2 hp,but good points. Most post what they read or internet info.Keep it safe and don't try to get it too tight.
Last edited by goldmember; 12/28/08 12:30 AM.
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Re: Positive vs. negative piston deck height
[Re: 360view]
#173204
12/28/08 01:39 AM
12/28/08 01:39 AM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
it is worth pondering the "crevice volume" effect
crevice volume is generally thought to be a bad thing because it 'quenches' the flame and creates unburned hydrocarbons ... which reduces both power and fuel economy
there is crevice volume in the little gaps of the head gasket joint
there is crevice volume in the 'ring land' from the top of the first ring to the piston crown
could the undesired two crevice volumes be combined to eliminate a bit of both?
some engine builders try to do this by having the piston come above the deck enough to cover the head gasket joint during the peak of the combustion event
it is an approach that might gain a bit of power and fuel economy
in one of the last 'Engine Masters' competitions one of the top engines had a very large value for positive deck and this may have been one of his strategies
there is also a small effect in being able to use a tiny bit longer connecting rod
it is worth thinking about
another small detail
"The Devil is in the Details"
I like that idea as you described it.mike
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Re: Positive vs. negative piston deck height
[Re: Sport440]
#173205
12/30/08 12:23 PM
12/30/08 12:23 PM
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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