Re: Pump gas compression
[Re: 6pkScamp]
#1424792
04/24/13 11:54 AM
04/24/13 11:54 AM
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Joined: Jan 2003
Posts: 6,266 Renton Washington
Triple Threat
master
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master
Joined: Jan 2003
Posts: 6,266
Renton Washington
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I ran 92 octane pump gas in my 11.3:1 390" small block stroker. Edelbrock heads and 263/268@.050 solid FT cam.
I never measured cylinder pressure.
-Dustin 67 Dart, 9 second, 392" G3 Hemi 68 Barracuda 340 F/SA
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Re: Pump gas compression
[Re: 383man]
#1424794
04/24/13 12:26 PM
04/24/13 12:26 PM
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Joined: Dec 2006
Posts: 1,178 Indy
FlyFish
super stock
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super stock
Joined: Dec 2006
Posts: 1,178
Indy
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410 stroker, edelbrocks, 10.89:1 compression, 248/254 @ 0.050 solid roller and it runs on premium pump gas.
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Pump gas compression
[Re: 6pkScamp]
#1424795
04/24/13 01:25 PM
04/24/13 01:25 PM
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Joined: Nov 2006
Posts: 635 mississippi
bentwheel43
mopar
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mopar
Joined: Nov 2006
Posts: 635
mississippi
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I have 512"kit, 12.42 Eddy heads,street roller cam,pumps 185# pressure on 93 pumpgas.I think the pumping pressure is the key.No gain with 110 racegas,no gain from 33* or 36* on the timing.308*/.575" cam installed@ 106*.
Last edited by bentwheel43; 04/24/13 01:28 PM.
Section 8 Racing We are nuts about racing.
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Re: Pump gas compression
[Re: 6pkScamp]
#1424796
04/24/13 03:17 PM
04/24/13 03:17 PM
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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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Your cam will dictate alot of your question(when the intake valve really closes is when you start making compression) but on my 416 with W-5 heads and a static compression of 10.7 and 260/270 105 lsa installed at 105 and the timing at 39*... it made 550 hp on 93 octane and if I pull 2* or 3* it will run on 87 no problem
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Re: Pump gas compression
[Re: 6pkScamp]
#1424797
04/24/13 04:24 PM
04/24/13 04:24 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 only crank at 170psi. Probably why my car is such a dud.
Mopar Performance
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Re: Pump gas compression
[Re: moparniac]
#1424798
04/24/13 07:44 PM
04/24/13 07:44 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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My stroker small block, 394 cubic in.is 10.9 to one has a 255/266 at .050 cam, cylinder pressure is in the 190's. Run it on 93 octane. 35* timing.
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: Pump gas compression
[Re: Dunnuck Racing]
#1424801
04/24/13 11:02 PM
04/24/13 11:02 PM
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Joined: May 2011
Posts: 625 Oakville, Wa
HOTMOPR
mopar
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mopar
Joined: May 2011
Posts: 625
Oakville, Wa
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Is there a general rule of thumb that says with a certain compression you should be running a certain octane gas? I always wondered how much you could push it. Such as a 9-1 motor on 8 psi is almost 14-1 total compression. Give or take.
67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
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Re: Pump gas compression
[Re: HOTMOPR]
#1424802
04/24/13 11:12 PM
04/24/13 11:12 PM
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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:
Is there a general rule of thumb that says with a certain compression you should be running a certain octane gas? I always wondered how much you could push it. Such as a 9-1 motor on 8 psi is almost 14-1 total compression. Give or take.
There are still the other factors that have been said.. the static compression number is just that... its a mathematical figure of what the area is with the piston up and down.... if the intake closes when the piston is half way up verses if it closed with the piston at the bottom they both still have the same static compression value but they sure wont be the same
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Re: Pump gas compression
[Re: Thumperdart]
#1424804
04/24/13 11:24 PM
04/24/13 11:24 PM
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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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I just had a thread about my struggles with my 10.2.1 iron headed BB when I switched from auto to manual trans. I used to run fine on pump 91 and 37 degrees total with a converter that flashed to 3500. And with the manual trans it was a ping fest until went to 35 total, a lighter spring in the dizzy and one step colder plugs. I can get it to ping still a little if I'm in 3rd and stand on it at 1500 rpm so I just don't do that.
Mopar to the bone!!!
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Re: Pump gas compression
[Re: 72Swinger]
#1424806
04/25/13 02:37 AM
04/25/13 02:37 AM
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Joined: Nov 2009
Posts: 520 New Zealand
nz383man
mopar
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mopar
Joined: Nov 2009
Posts: 520
New Zealand
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Quote:
I just had a thread about my struggles with my 10.2.1 iron headed BB when I switched from auto to manual trans. I used to run fine on pump 91 and 37 degrees total with a converter that flashed to 3500. And with the manual trans it was a ping fest until went to 35 total, a lighter spring in the dizzy and one step colder plugs. I can get it to ping still a little if I'm in 3rd and stand on it at 1500 rpm so I just don't do that.
I'm also of the belief you can run higher compression with a higher stall converter as you are removing the load at low RPM, where ping is usually at it's worst.
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Re: Pump gas compression
[Re: 572charger]
#1424810
04/26/13 05:58 AM
04/26/13 05:58 AM
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Joined: Nov 2009
Posts: 520 New Zealand
nz383man
mopar
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mopar
Joined: Nov 2009
Posts: 520
New Zealand
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Quote:
my pumpgas hemi is 12.1 to 1 comp but its a big roller cam/ only has 185#s cranking comp it goes 2 tenths SLOWER on 112 race gas !! all the wedges i build with aluminum heads i shoot for 11 to 1 comp on pump gas its pretty safe with a good cooling system !![aluminum radiator ]
OK, so what compression would you run an alloy head 484ci Hemi at with a roller cam 268*/264* @ .050 & .637"/.634" street strip E-Body, pump gas here in NZ is 95-96 but some stations have 98 Cheers
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