Commpression
#932152
02/19/11 02:04 AM
02/19/11 02:04 AM
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Joined: Feb 2010
Posts: 38
Canada
69 GTX
OP
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OP
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Joined: Feb 2010
Posts: 38
Canada
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I have tryed to figure out how to use those online CR formulas with no luck, can someone give me a figure on my CR with these componets,440 bored 30 over 4.350, stock deck height using stock length H beam rods,6.768 with Ross 99501 dome pistons,2v/v relieves,comp dist 1.273,dome height 0.640, piston head volume -50cc, comp height 2.065, dome volume -14cc.On top is a set of stock Stealth Heads with a .040 head gasket,also cam is Comp 284H with Crane 1/6 roller rockers with a lift of 541 in and 544 ex intake opens at 36 BTDC and closes 68 ABDC, EX opens 82 BBDC and closes 34 ATDC, Duration @.50 In 240, Ex 246,Valve timing 0.006 Lobe center 110,intake centerline 106 Thanks very much for any info, Rodger
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Re: Commpression
[Re: 69 GTX]
#932153
02/19/11 02:52 AM
02/19/11 02:52 AM
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Joined: Jan 2003
Posts: 75,020
U.S.S.A.
JohnRR
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I Win
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Some of your things do not compute , first off there is no H beam rod that is STOCK length , all except for a manely which is not available anymore, are 6.760 . Then your piston volumes, -50 and a dome of -14 ???? A dome with a NEGATIVE volume is a DISH Compression distance of 1.273 but a compression height of 2.065 ???? No wonder you can't figure out your compression ratio  edit ... i goofed the rod length , damm dyslexia
Last edited by JohnRR; 02/20/11 04:38 PM.
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Re: Commpression
[Re: 69 GTX]
#932155
02/19/11 12:11 PM
02/19/11 12:11 PM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
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Ontario, Canada
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So you have a 2.065 compression height piston with a 14 cc dome and stealth heads in a + .030 440 with a .040 gasket. You compression will be about 12.5 to 1 Stroke 3.75 deck 0 deck Dome - 14 cc Head 83 cc average gasket .040 average about 10 CC Displaces 913 cc per cylinder effective volume 83 + 10 - 14 = 79 913 + 79/79 = 12.55 to 1 
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Re: Commpression
[Re: 69 GTX]
#932156
02/19/11 12:14 PM
02/19/11 12:14 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Rodger get the correct specs & plug em in & see what you really have & head CC's and deck height figures you really need to measure what you actually have as listed specs are not accurate. The KB calculator is simple/accurate for SCR but to add in your cam specs etc for DCR you'd want a diff calculator (not sure which one, maybe Wallace racing ones which have been mentioned on here)
live every 24 hour block of time like it's your last day on earth
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Re: Commpression
[Re: Dodgem]
#932159
02/19/11 06:39 PM
02/19/11 06:39 PM
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Joined: Feb 2005
Posts: 4,314
Prospect, PA
BSB67
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Prospect, PA
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Quote:
So you have a 2.065 compression height piston with a 14 cc dome and stealth heads in a + .030 440 with a .040 gasket.
You compression will be about 12.5 to 1
Stroke 3.75
deck 0 deck
Dome - 14 cc
Head 83 cc average
gasket .040 average about 10 CC
Displaces 913 cc per cylinder
effective volume 83 + 10 - 14 = 79
913 + 79/79 = 12.55 to 1
Is your presumption that "stock deck height" is the same a bluprinted deck height?, verses factory actual deck height?
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Re: Commpression
[Re: Dodgem]
#932160
02/19/11 08:02 PM
02/19/11 08:02 PM
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Joined: Oct 2005
Posts: 4,946
WI
Dcuda69
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Quote:
No stock length H beam rods better tell eagle
http://chucker54.stores.yahoo.net/corodse1.html
Those rods are listed at 6.760...I believe stock length is 6.768. It's only .008 but  i went through that when I did my low deck stroker,got some of the last Manleys that are a true 6.768 rod as JohnRR said.
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Re: Commpression
[Re: Dodgem]
#932161
02/20/11 04:24 PM
02/20/11 04:24 PM
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Joined: Jan 2003
Posts: 75,020
U.S.S.A.
JohnRR
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Quote:
No stock length H beam rods better tell eagle
http://chucker54.stores.yahoo.net/corodse1.html
Maybe you should contact your optometrist because you obviously can NOT read what's written there. A STOCK length RB rod is 6.768 the Eagle , as are most ALL aftermarket rods , are 6.760.
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Re: Commpression
[Re: Dcuda69]
#932162
02/20/11 04:27 PM
02/20/11 04:27 PM
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Joined: Jan 2003
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U.S.S.A.
JohnRR
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Quote:
Quote:
No stock length H beam rods better tell eagle
http://chucker54.stores.yahoo.net/corodse1.html
Those rods are listed at 6.760...I believe stock length is 6.768. It's only .008 but i went through that when I did my low deck stroker,got some of the last Manleys that are a true 6.768 rod as JohnRR said.
It may be only .008 but it starts to add up once you start adding in other market parts that are shorter than factory , the shorter rod and a piston that is already .020 in the hole is now .028 , if you are trying to build a quench engine you are now .008 further away ....
The Manleys that were available were 6.765 , which is closer but ...
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Re: Commpression
[Re: BSB67]
#932163
02/20/11 04:33 PM
02/20/11 04:33 PM
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JohnRR
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Quote:
Quote:
So you have a 2.065 compression height piston with a 14 cc dome and stealth heads in a + .030 440 with a .040 gasket.
You compression will be about 12.5 to 1
Stroke 3.75
deck 0 deck
Dome - 14 cc
Head 83 cc average
gasket .040 average about 10 CC
Displaces 913 cc per cylinder
effective volume 83 + 10 - 14 = 79
913 + 79/79 = 12.55 to 1
Is your presumption that "stock deck height" is the same a blueprinted deck height?, verses factory actual deck height?
Nevermind that he can't read he can't add either , a 2.065 piston on a 6.768 rod in a 10.725 factory deck is .017 IN THE HOLE , put it on his shorter 6.760 rod and now it's .025 in the hole .
Or is that zero deck when you convert from metric to decimal ??? 
Using the above specs, 6.760 rod I get 11.59
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Re: Commpression
[Re: JohnRR]
#932164
02/21/11 01:32 PM
02/21/11 01:32 PM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
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Some of you guys are way to anal! .008 really blueprint really. Yes it was a generalization of being within spec. Short of actual ccing which i doubt you guys have the equipment to do to be exact it does end up ballpark. 
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Re: Commpression
[Re: Dodgem]
#932165
02/21/11 02:28 PM
02/21/11 02:28 PM
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Posts: 75,020
U.S.S.A.
JohnRR
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I Win
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Quote:
Some of you guys are way to anal!
.008 really blueprint really.
Yes it was a generalization of being within spec.
Short of actual ccing which i doubt you guys have the equipment to do to be exact it does end up ballpark.
.025 in the hole is more like grand canyon than ballpark ...
I'll post up a pic of my burret later for you if you'd like .
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Re: Commpression
[Re: Dodgem]
#932166
02/21/11 02:45 PM
02/21/11 02:45 PM
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Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
64Post
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Baltimore/Denver
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Quote:
Your dynamic compression ratio is 10.95 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 237.43 PSI.
237 psi can't be correct.
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Re: Commpression
[Re: Dodgem]
#932168
02/21/11 04:02 PM
02/21/11 04:02 PM
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JohnRR
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Quote:
well if you go to the low side of tolerances 225 tat 12 to 1 with that cam piston has a 14cc dome
It has a 14 cc dome but does that also include the valve reliefs ? If it does that's closer to a 20cc dome, which is pretty big .
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Re: Commpression
[Re: 64Post]
#932170
02/22/11 03:02 PM
02/22/11 03:02 PM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
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Ontario, Canada
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Normally a piston spec includes the valve notch so a -14 cc dome is gross just as a + 14 cc dish would include the valve notches in that number. http://www.rbracing-rsr.com/comprAdvHD.htmThis calculator uses @.050 numbers on the calculation so a 240 at .050 intake lobe is 240/2 = 120 then the install is 106 so 74 deg remain to bdc you take the remaining 120 deg and subtracted the 74 from it leaving 46 degrees @.050 ABDC boost is 0. It gives me 225 and 10.5 This calculator has been withing 7 to 8 lb actual average cranking compression on my last three motors and numerous friends motors.
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