Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2744907
02/20/20 12:00 PM
02/20/20 12:00 PM
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Joined: Oct 2005
Posts: 265 Anchorage, Alaska
metallicareload
enthusiast
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enthusiast
Joined: Oct 2005
Posts: 265
Anchorage, Alaska
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Smog 440, big old iron open chamber heads, atleast 36⁰+ of timing, any octane:
Average of all 8 hot is 142 psi
Last edited by metallicareload; 02/20/20 12:01 PM.
440, 4-Speed, 3.54 1968, when Dinosaurs ruled the Earth
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Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2744913
02/20/20 12:16 PM
02/20/20 12:16 PM
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Joined: Jan 2003
Posts: 13,318 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,318
Marion, South Carolina [><]
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The cranking pressure won't tell you much. I have an aluminum head 11:1 hemi that cranks 185 psi and runs on pump gas w/ 34°. Also have an aluminum head 14.5:1 wedge that cranks 185 psi and needs 112 fuel. The same motor w/ a different camshaft cranked 275 psi and also ran 112 fuel. Both run at 38°. Had an iron head 12:1 440 years ago that cranked 220 psi and needed 110 fuel at 38°.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Data request, what is your cranking PSI?
[Re: Mr PotatoHead]
#2744935
02/20/20 01:56 PM
02/20/20 01:56 PM
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Joined: Jan 2003
Posts: 19,304 Las Vegas
Al_Alguire
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I Live Here
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Posts: 19,304
Las Vegas
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My Predatoer is fairly low, but being an aluminum block they usually are. It is 210ish per hole, Q16 fuel 39 degrees in first gear and 33 in high gear, This is a 1200HP 15.8-1 engine. When it gets freshened later this year we will be going closer to 17-1 in an effort to up the cylinder pressure. FWIW the heads up car, aluminum block again only pumps about 175, its 16.4-1 runs on C45 and we have timing curves for each gear
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Data request, what is your cranking PSI?
[Re: Al_Alguire]
#2744964
02/20/20 03:21 PM
02/20/20 03:21 PM
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Joined: Jan 2003
Posts: 3,122 Auburn WA
Dave_J
master
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master
Joined: Jan 2003
Posts: 3,122
Auburn WA
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Like said, this will not tell too much. 1984 Shelby 2.2, 0.039" over flat pistons with ported Aluminum G head, 252 deg cam (0.460 lift) installed 4 deg advanced , 0.030 cut on block, true measured 11.2:1 compression ratio. 20 degrees base timing, with factory Shelby computer and knock sensor. It would show 215 PSI warm. It ran on pump SUPER. Shifted at 7200 RPM. Top speed on 85 MPH speedo was 15 MPH UPDATAED^^^
Last edited by Dave_J; 02/20/20 06:00 PM.
Retired, US ARMY 1973-1994 ASE mechanic, Electrical 1994-1997 Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter 65 Formula S Cuda 78 Little Red Express Truck 98 Buick Regal (wifes car)
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Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2744979
02/20/20 03:59 PM
02/20/20 03:59 PM
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Joined: Mar 2007
Posts: 3,275 West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,275
West Coast, USA
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10.2 to 1 in both my 493" RB & 408" Magnum. Both have aluminum heads, pistons 0 decked with high quench heart shaped chambers. The RB has reverse dome that matches the Indy EZ chambers. The Magnum has flat top pistons with Eddie heads.
Both motors crank 200 psi warm. I run 35* total advance locked in on the RB and reflashed factory JTEK computer controlled on the 408. They both run on California 91 ethanol pump swill. No detonation even on hot days.
(Installed on 105* centerline)
Last edited by jbc426; 02/21/20 12:21 PM.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Data request, what is your cranking PSI?
[Re: MR_P_BODY]
#2745028
02/20/20 07:28 PM
02/20/20 07:28 PM
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Joined: Jan 2003
Posts: 9,963 Frostbitefalls MN (Rocky&Bullw...
gregsdart
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master
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Posts: 9,963
Frostbitefalls MN (Rocky&Bullw...
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I have a H ones inverse ground roller cam and he uses VERY long lash ramps. If you are a few degrees off when setting lash it can make a noticeable difference in opening point. Add to that aluminum block and heads and things must change a bunch from running cold to hot.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2745038
02/20/20 08:06 PM
02/20/20 08:06 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
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master
Joined: Oct 2007
Posts: 4,205
New York
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Not enough data: missing IVC closing ABDC, rod ratio, intake vacuum during test. CCP is useful to compare the same (or almost identical) engine(s) with different tunes, not to compare different engines.
Boffin Emeritus
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Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2745092
02/21/20 12:28 AM
02/21/20 12:28 AM
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Joined: Jan 2003
Posts: 1,753 Windsor, ON, Canada
Diplomat360
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,753
Windsor, ON, Canada
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Hughes Engines HE3844AL hydraulic flat tappet cam, specs are: see attachment.
This is in a semi-blueprinted 360 block at 10.5:1 CR, cranking some 185 PSI @hot.
Engine runs on 91 pump gas, 21 initial and 38 total mechanical advance.
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Re: Data request, what is your cranking PSI?
[Re: Diplomat360]
#2745211
02/21/20 01:17 PM
02/21/20 01:17 PM
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Joined: Jan 2003
Posts: 19,304 Las Vegas
Al_Alguire
I Live Here
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I Live Here
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Las Vegas
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The two examples I listed might scare to many in here if they knew the cam specs
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Data request, what is your cranking PSI?
[Re: 73DAD]
#2745307
02/21/20 08:43 PM
02/21/20 08:43 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
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master
Joined: Oct 2007
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New York
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The same CCP can be arrived at by many different combinations of CR & IVC, like late IC + high CR or early IC + low CR may produce the same CCP at cranking speed. The cylinder combustion pressure of the low CR will rise immediately but not that much, the high CR will take longer (delayed VE and torque curve) but get much higher. Two engines with the same CCP, produced the same way, may not have the same knock sensitivity.
Things to avoid: using the wrong cam (not the optimum choice for best power characteristics) to change cranking pressure.
Overlap has nothing to do with CCP, but it definitely affects knock sensitivity by retaining exhaust gas in the chamber.
Boffin Emeritus
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Re: Data request, what is your cranking PSI?
[Re: polyspheric]
#2746011
02/24/20 09:43 AM
02/24/20 09:43 AM
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Joined: Jan 2003
Posts: 13,318 Marion, South Carolina [><]
an8sec70cuda
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I Live Here
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Marion, South Carolina [><]
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It seems to me that the OP is trying to judge what octane you can run by the cranking compression of the engine. That's not gonna work.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Data request, what is your cranking PSI?
[Re: an8sec70cuda]
#2746100
02/24/20 02:27 PM
02/24/20 02:27 PM
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Joined: Jun 2015
Posts: 310 Northeast Indiana
73DAD
OP
enthusiast
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OP
enthusiast
Joined: Jun 2015
Posts: 310
Northeast Indiana
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It seems to me that the OP is trying to judge what octane you can run by the cranking compression of the engine. That's not gonna work. I didn't say that, nor imply it. Thanks to all those that have contributed to the thread.
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