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Data request, what is your cranking PSI? #2744902
02/20/20 11:43 AM
02/20/20 11:43 AM
Joined: Jun 2015
Posts: 215
Northeast Indiana
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73DAD Offline OP
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73DAD  Offline OP
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Joined: Jun 2015
Posts: 215
Northeast Indiana
What is your cranking PSI? Please specify hot or cold.

&...

What octane can you run?
How much advance are you running?
What combustion chamber?
Alum or Iron heads?

The more info the better, thanks!

I plan on doing a cranking pressure test to see if I'm high or low. The problem is, I have no frame of reference for this & would like to hear what others have. I'd bet there are plenty of others on this forum that would find this information interesting or useful too.

Re: Data request, what is your cranking PSI? [Re: 73DAD] #2744907
02/20/20 12:00 PM
02/20/20 12:00 PM
Joined: Oct 2005
Posts: 5
Anchorage, Alaska
metallicareload Offline
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metallicareload  Offline
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Anchorage, Alaska
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.

1968, when Dinosaurs ruled the Earth
Re: Data request, what is your cranking PSI? [Re: 73DAD] #2744913
02/20/20 12:16 PM
02/20/20 12:16 PM
Joined: Jan 2003
Posts: 11,725
Marion, South Carolina [><]
an8sec70cuda Offline
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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 street car...8.91 at 150.5 mph w/ 4.10s, 8.97 at 152.5 mph w/ 3.54s so far
'69 road runner 440 w/ Indy SRs
'69 road runner 440-6, 4 speed...Dad's ride
'71 Demon 340 resto project
'06 GMC 2500HD LBZ Duramax...toy hauler
'16 Grand Caravan SXT...baby hauler
Re: Data request, what is your cranking PSI? [Re: an8sec70cuda] #2744914
02/20/20 12:20 PM
02/20/20 12:20 PM
Joined: Aug 2019
Posts: 496
Spudsville
Mr. Potatohead Offline
The member formerly known as..EV2..
Mr. Potatohead  Offline
The member formerly known as..EV2..

Joined: Aug 2019
Posts: 496
Spudsville
How is you car acting now?

What is your setup?


My family is a bunch of Fruits and Vegetables and many cant tell us apart. EAT ME!
Re: Data request, what is your cranking PSI? [Re: Mr. Potatohead] #2744935
02/20/20 01:56 PM
02/20/20 01:56 PM
Joined: Jan 2003
Posts: 17,354
Las Vegas
Al_Alguire Online laugh2
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Al_Alguire  Online laugh2
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Las Vegas
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

Re: Data request, what is your cranking PSI? [Re: Al_Alguire] #2744964
02/20/20 03:21 PM
02/20/20 03:21 PM
Joined: Jan 2003
Posts: 2,894
Auburn WA
Dave_J Offline
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Dave_J  Offline
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Auburn WA
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 wink

UPDATAED^^^

Last edited by Dave_J; 02/20/20 06:00 PM.

SSG/E-6 Retired, US ARMY 1973-1994
Retired GTE/VERIZON/FRONTIER 1997-2015

Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, most good.

03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
Re: Data request, what is your cranking PSI? [Re: 73DAD] #2744979
02/20/20 03:59 PM
02/20/20 03:59 PM
Joined: Mar 2007
Posts: 2,946
West Coast, USA
jbc426 Online content
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jbc426  Online Content
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Posts: 2,946
West Coast, USA
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 3.91's (closest thing to an automatic 5 speed going)
Re: Data request, what is your cranking PSI? [Re: jbc426] #2744990
02/20/20 04:37 PM
02/20/20 04:37 PM
Joined: Jun 2003
Posts: 51,616
Romeo MI
MR_P_BODY Online content
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MR_P_BODY  Online Content
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Posts: 51,616
Romeo MI
No one says where the cam is installed.. advancing or retarding it will change your cyl pressure
wave

Re: Data request, what is your cranking PSI? [Re: MR_P_BODY] #2744992
02/20/20 04:39 PM
02/20/20 04:39 PM
Joined: Jun 2008
Posts: 3,114
usa
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lewtot184 Offline
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lewtot184  Offline
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usa
Originally Posted by MR_P_BODY
No one says where the cam is installed.. advancing or retarding it will change your cyl pressure
wave
I think the real question is when does the intake valve close.

Re: Data request, what is your cranking PSI? [Re: lewtot184] #2744995
02/20/20 04:44 PM
02/20/20 04:44 PM
Joined: Jun 2003
Posts: 51,616
Romeo MI
MR_P_BODY Online content
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MR_P_BODY  Online Content
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Romeo MI
It is the question I think
wave

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
Joined: Jan 2003
Posts: 8,723
Frostbitefalls (Rocky&Bullwink...
gregsdart Offline
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gregsdart  Offline
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Frostbitefalls (Rocky&Bullwink...
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.

Re: Data request, what is your cranking PSI? [Re: 73DAD] #2745038
02/20/20 08:06 PM
02/20/20 08:06 PM
Joined: Oct 2007
Posts: 3,456
New York
polyspheric Offline
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polyspheric  Offline
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New York
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
Re: Data request, what is your cranking PSI? [Re: 73DAD] #2745092
02/21/20 12:28 AM
02/21/20 12:28 AM
Joined: Jan 2003
Posts: 1,312
Windsor, ON, Canada
D
Diplomat360 Offline
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Diplomat360  Offline
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Posts: 1,312
Windsor, ON, Canada
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.

HUGHES - HE3844AL Cam Card.jpg
Re: Data request, what is your cranking PSI? [Re: Diplomat360] #2745211
02/21/20 01:17 PM
02/21/20 01:17 PM
Joined: Jan 2003
Posts: 17,354
Las Vegas
Al_Alguire Online laugh2
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Al_Alguire  Online laugh2
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Las Vegas
The two examples I listed might scare to many in here if they knew the cam specs

Re: Data request, what is your cranking PSI? [Re: Al_Alguire] #2745266
02/21/20 05:15 PM
02/21/20 05:15 PM
Joined: Sep 2006
Posts: 1,382
central ohio
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nss guy Offline
pro stock
nss guy  Offline
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Joined: Sep 2006
Posts: 1,382
central ohio
mines 210-215psi , 499ci
cam specs.

cam specs1.jpg
Re: Data request, what is your cranking PSI? [Re: nss guy] #2745282
02/21/20 06:31 PM
02/21/20 06:31 PM
Joined: Sep 2006
Posts: 1,382
central ohio
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nss guy Offline
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Posts: 1,382
central ohio
Installed at 106

Re: Data request, what is your cranking PSI? [Re: 73DAD] #2745307
02/21/20 08:43 PM
02/21/20 08:43 PM
Joined: Oct 2007
Posts: 3,456
New York
polyspheric Offline
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polyspheric  Offline
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New York
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
Re: Data request, what is your cranking PSI? [Re: polyspheric] #2746011
02/24/20 09:43 AM
02/24/20 09:43 AM
Joined: Jan 2003
Posts: 11,725
Marion, South Carolina [><]
an8sec70cuda Offline
I Live Here
an8sec70cuda  Offline
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Posts: 11,725
Marion, South Carolina [><]
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 street car...8.91 at 150.5 mph w/ 4.10s, 8.97 at 152.5 mph w/ 3.54s so far
'69 road runner 440 w/ Indy SRs
'69 road runner 440-6, 4 speed...Dad's ride
'71 Demon 340 resto project
'06 GMC 2500HD LBZ Duramax...toy hauler
'16 Grand Caravan SXT...baby hauler
Re: Data request, what is your cranking PSI? [Re: an8sec70cuda] #2746100
02/24/20 02:27 PM
02/24/20 02:27 PM
Joined: Jun 2015
Posts: 215
Northeast Indiana
7
73DAD Offline OP
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73DAD  Offline OP
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Posts: 215
Northeast Indiana
Originally Posted by an8sec70cuda
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.

Re: Data request, what is your cranking PSI? [Re: 73DAD] #2746116
02/24/20 03:00 PM
02/24/20 03:00 PM
Joined: Jun 2008
Posts: 3,114
usa
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lewtot184 Offline
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lewtot184  Offline
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usa
for what it's worth one of my 440's does 160psi cold. might do 170 hot. 9.8:1static compression ratio, alum heads. closes the intake valve at 76 degrees after BDC. very pump gas friendly with 93 octane.


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