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What cylinder pressure on pump gas?
#1792663
03/31/15 04:55 PM
03/31/15 04:55 PM
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Joined: May 2008
Posts: 984
San Diego CA
65 Hemi
OP
super stock
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OP
super stock
Joined: May 2008
Posts: 984
San Diego CA
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Changing my Hemi over to pump gas. What cylinder pressure can I get away with on 92 pump gas? All aluminum 4.50 bore motor.
Doug
MOPAR or NO CAR!!!
1965 Dodge Coronet soon a 6.1 Hemi with a Magnson blower 810 hp on pump gas
1964 Dodge Polara 582" Indy alum Block 426-1RA heads,
1933 Plymouth PE all Steel, LT1 4L60E
1959 Plymouth Savoy 33,000 mile survivor
Old cars are never done. They are ongoing projects!
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Re: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792664
03/31/15 04:59 PM
03/31/15 04:59 PM
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Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
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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: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792666
03/31/15 05:48 PM
03/31/15 05:48 PM
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Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
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You're welcome.  My 14:1 wedge motor also has 185 psi...definitely not running pump 93 in that one though. 
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: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792668
03/31/15 08:15 PM
03/31/15 08:15 PM
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Joined: Oct 2009
Posts: 1,267
North, Alabama
D-50
pro stock
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pro stock
Joined: Oct 2009
Posts: 1,267
North, Alabama
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I run 93 octane in my small block and I have 195-201 lb cranking cylinder pressure. 10.9-1 comp, .255/.266 @.050 camshaft with aluminum heads. Distributor locked out at 35 degrees.
1.33 60 ft,6.21 at 110.59 in the 1/8, pump gas small block,2950lbs,drag radials,mufflers and driven to track ...
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Re: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792670
04/01/15 01:08 PM
04/01/15 01:08 PM
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Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
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Quote:
Quote:
You're welcome. My 14:1 wedge motor also has 185 psi...definitely not running pump 93 in that one though.
Yes, it's a little tougher to run that high of cylinder pressure in a wedge.
The wedge had 275 psi before I changed the cam. 
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: What cylinder pressure on pump gas?
[Re: 68LAR]
#1792672
04/01/15 04:18 PM
04/01/15 04:18 PM
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Joined: Feb 2007
Posts: 6,295
U.S.
moparniac
master
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master
Joined: Feb 2007
Posts: 6,295
U.S.
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I crank at 170, I run 9s on local 93 gas.
Mopar Performance
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Re: What cylinder pressure on pump gas?
[Re: moparniac]
#1792673
04/01/15 06:26 PM
04/01/15 06:26 PM
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Joined: Oct 2007
Posts: 3,978
Hilltown Pa
1967dartgt
master
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master
Joined: Oct 2007
Posts: 3,978
Hilltown Pa
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I have 190s on pump puke.
Brett Miller W9 cnc'd heads
STR Chassis fabraction
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Re: What cylinder pressure on pump gas?
[Re: 1967dartgt]
#1792674
04/01/15 08:28 PM
04/01/15 08:28 PM
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Joined: Jan 2011
Posts: 4,785
Utah and Alaska
astjp2
master
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master
Joined: Jan 2011
Posts: 4,785
Utah and Alaska
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212 psi is a little too high.
1941 Taylorcraft
1968 Charger
1994 Wrangler
1998 Wrangler
2008 Kia Rio
2017 Jetta
I didn't do 4 years and 9 months of Graduate School to be called Mister!
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Re: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792676
04/01/15 08:43 PM
04/01/15 08:43 PM
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Joined: Jan 2003
Posts: 9,994
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,994
Frostbitefalls MN (Rocky&Bullw...
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There was a point made in one of the posts on compression and pump gas that the true test is how well it will run when the motor hits the peak torque area where max volumetric efficiency is achieved. With a big cam and high compression the motor will still need the octane to handle the static (not cranking) compression due to ram intake and exhaust tuning.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: What cylinder pressure on pump gas?
[Re: 1980volare]
#1792677
04/02/15 10:17 AM
04/02/15 10:17 AM
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Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,360
Marion, South Carolina [><]
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Quote:
Cylinder pressure is not directly related to compression ratio. You need to know cam specs, bore, stroke, rod length, static compression, and valve closing angle. other wise you're just guessing.
 Just b/c my wedge cranks 185 psi doesn't mean it'll run on 93. It still has the same 14+:1 compression it did before when it cranked 275 psi...the cam is the only difference.
The compression ratio still needs to be on the low end (for the most part) to be pump gas friendly.
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: What cylinder pressure on pump gas?
[Re: 65 Hemi]
#1792678
04/03/15 01:50 PM
04/03/15 01:50 PM
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Joined: Jan 2003
Posts: 1,758
Windsor, ON, Canada
Diplomat360
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,758
Windsor, ON, Canada
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360 mopar, 9.8:1 CR, 175 PSI cranking with a Hughes hydraulic flat tappet cam: 238/244 @ 0.050, with nasty/crappy quench on stock heads. I run 93/94 pump gas...pretty aggresive advance curve: 21 idle@900, 35 @2000. No ping.
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Re: What cylinder pressure on pump gas?
[Re: Diplomat360]
#1792679
04/03/15 05:22 PM
04/03/15 05:22 PM
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Joined: May 2004
Posts: 12,386
Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
Joined: May 2004
Posts: 12,386
Taxes & Virus's R-US, NY
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Quote:
360 mopar, 9.8:1 CR, 175 PSI cranking with a Hughes hydraulic flat tappet cam: 238/244 @ 0.050, with nasty/crappy quench on stock heads. I run 93/94 pump gas...pretty aggresive advance curve: 21 [Email]idle@900[/Email], 35 @2000. No ping.
I would advance final timning even more on that one. All my low compression 340's and 360's liked at least 38...
And for the nay sayers, you can run 14:1 on pump gas....Its called water injection and it works really well. If you can tune a carb, you can tune a water injection system. We have guys tired of paying for race fuel and went this route and will never look back.
Last edited by Dragula; 04/03/15 05:24 PM.
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Re: What cylinder pressure on pump gas?
[Re: 572charger]
#1792681
04/06/15 11:58 AM
04/06/15 11:58 AM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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With a loose verter you can get away with 185-195 all day long. Go to a manual trans with the same setup and plan on taking about 5-6 degrees out of total timing or it will be ping city.
Mopar to the bone!!!
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