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detonation vs compression, static or dynamic??
#1471154
07/21/13 01:44 AM
07/21/13 01:44 AM
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Joined: Jan 2003
Posts: 1,255
Columbus, GA
Michael Ecks
OP
pro stock
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OP
pro stock
Joined: Jan 2003
Posts: 1,255
Columbus, GA
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Playing with numbers on my night off. Using the compression ration calculator on the kb-silvolite website using the the parts I am considering for my build I come up with very different numbers. 10.929 static that's way too high for pump gas, but 9.420 dynamic which seems okay if I am understanding quench correctly. So which one is the important one for avoiding detonation problems, as I am planning a pump gas motor build? Static or dynamic? The combo I am looking at is a stock stroke 360, 4.040 KB107 pistons at zero deck, RHS X heads, Voodoo cam (Lift: .475/.494 Duration: 265/271 LSA: 112), and .039 Fel Pro head gaskets for .039 quench. Trying to learn and figure all this out before I start ordering parts and 
"The happiness of your life depends upon the quality of
your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471155
07/21/13 02:09 AM
07/21/13 02:09 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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Static is just a cyl volume thing(bottom to top with head and gasket).. it doesnt take into account when the valve closes and really starts the compression stroke 
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471157
07/21/13 02:18 AM
07/21/13 02:18 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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Quote:
Playing with numbers on my night off. Using the compression ration calculator on the kb-silvolite website using the the parts I am considering for my build I come up with very different numbers. 10.929 static that's way too high for pump gas, but 9.420 dynamic which seems okay if I am understanding quench correctly.
So which one is the important one for avoiding detonation problems, as I am planning a pump gas motor build? Static or dynamic?
The combo I am looking at is a stock stroke 360, 4.040 KB107 pistons at zero deck, RHS X heads, Voodoo cam (Lift: .475/.494 Duration: 265/271 LSA: 112), and .039 Fel Pro head gaskets for .039 quench.
Trying to learn and figure all this out before I start ordering parts and
Is that duration at .050 or what.. thats alot of duration
for a small lift(I dont know the Voodoo stuff) other
than a fancy name
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471160
07/21/13 03:17 AM
07/21/13 03:17 AM
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Joined: Feb 2004
Posts: 4,501
Gainesville,FL
goldmember
master
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master
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
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Quote:
Quote:
Not even close to a workable combo of parts on pump gas.
Didn't think so. I think I found the error in my math and it leaves me with a dynamic of 10.38. 
I could switch to speed-pro's .015 in the hole and thick gaskets which would put me at static 10.14:1/dynamic 9.64:1. But then I've lost all quench! 
Back to the drawing board I guess. Any recommendations? I was hoping to use hypereutetic pistons and have it run a little better than the mopar 380 crate engine.
without more info it's very hard to make a recommendation other than to say do not push the comp if your limited to pump gas. how does the 380hp crate engine run? Ported heads,better camshaft and intake may be all you need.
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471161
07/21/13 03:21 AM
07/21/13 03:21 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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If you went with more duration the pressure would be down during low rpm (which is the problem area) and still use the same piston BUT you have to take the revs higher ... but that also needs the head flow... just a thought... plus what are you talking for pump gas EDIT Plus a looser conv would help so you dont load the engine at low rpm... along with the rear gear.... my 416 is a 10.5 static but with a 260/270 at .050 cam and a 5000 stall conv and 4:10 gears in a some what lighter car
Last edited by MR_P_BODY; 07/21/13 03:32 AM.
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471162
07/21/13 11:26 AM
07/21/13 11:26 AM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
master
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master
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
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You are going with aluminum heads that is huge in resisting detonation. I do vote for the looser converter and bigger cam though. Do you have all the specs on heads head gasket pistons and so forth to do compression numbers?? 
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Re: detonation vs compression, static or dynamic??
[Re: Dodgem]
#1471164
07/21/13 11:43 AM
07/21/13 11:43 AM
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Joined: Mar 2003
Posts: 2,524
PA
moparacer
master
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master
Joined: Mar 2003
Posts: 2,524
PA
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You are way too small with the combustion chambers on the RHS heads right?
I ran into the same problem with 318 magnum heads and the flat top zero deck engine I put in my Barracuda.
The cheapest solution for me was to open the chambers up to 68 CC.
67 Barracuda street/bracket car 11.27-119
68 Dart 502 BB 8.70s-152
414 cid SB Dragster 7.65-174
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471165
07/21/13 04:03 PM
07/21/13 04:03 PM
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Joined: Dec 2010
Posts: 208
Norrland, Sweden
Swedcharger67
enthusiast
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enthusiast
Joined: Dec 2010
Posts: 208
Norrland, Sweden
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I think the dynamic one is the important one for considering the risk of detonation.
At higher revs the cylinder pressure may rise slightly, but the engine may at the same time be less prone to detonation.
Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection
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Re: detonation vs compression, static or dynamic??
[Re: moparacer]
#1471166
07/21/13 04:17 PM
07/21/13 04:17 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
Striving for excellence
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Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Are you sure the math is right?
The dynamic equation relies heavily on the intake closing @ .050 PLUS 15 degrees. I'm making some changes to avoid this very thing. I chose a Lunati Solid. This one closes at 57 degrees. With the 15 additional degrees it comes in at 71. That takes my 10.7 ratio down to a dynamic of 8.138.
I can't imagine that your static and dynamic can be so close to each other.
Even with my old '509 cam, I still had a dynamic reading of 8.8, so I think you may have made an error in calculating.
*******************************************************************
The stories I hear, anything above 190 psi cranking compression or 8.5 dynamic are getting into race gas territory.
Currently in my Charger I get an average psi between 185 and 192. I cannot run more than 31 degrees of advance. Even at 31 I'll get detonation at full throttle.
Last edited by Frankenduster; 07/21/13 06:29 PM.
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Re: detonation vs compression, static or dynamic??
[Re: Kern Dog]
#1471167
07/21/13 04:42 PM
07/21/13 04:42 PM
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Joined: Jan 2005
Posts: 12,423
Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,423
Kalispell Mt.
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It will be fine
I Run stock pistons with .035 quench in a 318 mag it a heavy high geared ram With a stock cam and have no detonation
Mag chambers and tight quench are awesome.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: detonation vs compression, static or dynamic??
[Re: 5spdcuda]
#1471169
07/21/13 11:24 PM
07/21/13 11:24 PM
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Joined: Jan 2003
Posts: 1,255
Columbus, GA
Michael Ecks
OP
pro stock
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OP
pro stock
Joined: Jan 2003
Posts: 1,255
Columbus, GA
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Thanks 5spd. That piston may be just what I need, I like lighter and it should get me the compression I was looking for.
My only question with them now is, can Eagle SIRs be safely narrowed to 1 inch on the small end? I have a set of SIR and factory magnums sitting here, and the small end looks similar thickness minus the factory ones balance pad and casting lines.
I know Eagle's don't have the best reputation anymore. Since this engine will never see nitros, and since I am going with light pistons instead of heavier forged I am hoping to get away with running them since I have them already.
"The happiness of your life depends upon the quality of
your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: detonation vs compression, static or dynamic??
[Re: Michael Ecks]
#1471170
07/22/13 01:14 AM
07/22/13 01:14 AM
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Joined: Nov 2004
Posts: 1,708
S. Il. U.S.A.
5spdcuda
top fuel
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top fuel
Joined: Nov 2004
Posts: 1,708
S. Il. U.S.A.
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Eagle "H" beams are no doubt stronger than the SIR's, but if it's any consolation I friend of mine used them in his .030 360 mid 10 sec. Dart and they held up. He crossed the stripe in the quarter at just over 7,000 rpm and shifted at 6,600. Pretty good for a budget built 360. I should point out that this was a really light car on alky. Still mid 10's at 124 mph and 7,000 rpm+ with KB hyper pistons and SIR rods ain't bad. I would check with your machine shop about narrowing them to 1 inch. I run the 362's with narrowed LA rods in my'Cuda. Pistons are under 600 grams with pins. I shift at 6,200, rev limiter is at 6,600 and I have bounced off it a few times. My engine is internally balanced FWIW.
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Re: detonation vs compression, static or dynamic??
[Re: Kern Dog]
#1471171
07/22/13 11:25 PM
07/22/13 11:25 PM
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Joined: May 2004
Posts: 1,522
Ste-Sophie, Quebec, Canada
Wedgeman
pro stock
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pro stock
Joined: May 2004
Posts: 1,522
Ste-Sophie, Quebec, Canada
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Quote:
Are you sure the math is right?
The dynamic equation relies heavily on the intake closing @ .050 PLUS 15 degrees. I'm making some changes to avoid this very thing. I chose a Lunati Solid. This one closes at 57 degrees. With the 15 additional degrees it comes in at 71. That takes my 10.7 ratio down to a dynamic of 8.138.
I can't imagine that your static and dynamic can be so close to each other.
Even with my old '509 cam, I still had a dynamic reading of 8.8, so I think you may have made an error in calculating.
*******************************************************************
The stories I hear, anything above 190 psi cranking compression or 8.5 dynamic are getting into race gas territory.
Currently in my Charger I get an average psi between 185 and 192. I cannot run more than 31 degrees of advance. Even at 31 I'll get detonation at full throttle.
Precisely,
do not forget to add 15 degrees to the closing point of the intake valve.
Pretty accurate from my experience.
I used the RHS before in my 408 and worked great !
Do not pass 9:1 dynamic c.r.
Dan
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Re: detonation vs compression, static or dynamic??
[Re: HotRodDave]
#1471173
07/23/13 08:26 AM
07/23/13 08:26 AM
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Joined: Jan 2005
Posts: 4,862
the frozen wastes...
Pale_Roader
Swears too much
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Swears too much
Joined: Jan 2005
Posts: 4,862
the frozen wastes...
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Quote:
It will be fine
I Run stock pistons with .035 quench in a 318 mag it a heavy high geared ram With a stock cam and have no detonation
Mag chambers and tight quench are awesome.
Sounds like something i've been thinking a lot about recently.
I'd be interested to know more about the combo...
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