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03-13-2011, 05:43 PM
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CC Member
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Join Date: Mar 2011
Cobra Make, Engine: #6101 streetbeast Ingelese stack EFI 351w/t-5 9" 4link 3.55
Posts: 277
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Not Ranked
Octane
Ok one more ? for tonight. I have a 425 hp/400tq 351w at 9.5 to1 compression. I'm going to run 93 octane, but should I use octane booster and if I do what boost 104, 106, 108? thanks. little w.
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03-13-2011, 06:00 PM
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Senior Club Cobra Member
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Join Date: Jun 2007
Location: Covington,
wa
Cobra Make, Engine: Superformance # 532, 466 BB, 560HP
Posts: 3,027
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Octane by it's self does not add power to an engine.
What it does is allow higher compression ratios, more timing advance, radical cam, etc. that does create more power.
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John Hall
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03-13-2011, 06:02 PM
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CC Member
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Join Date: Dec 2010
Location: Tempe,AZ-High Point,NC,
AZ
Cobra Make, Engine: Kirkham #684, 482FE, Mike Mccluskey build
Posts: 2,520
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9.5 compression is fine on 93 octane, it actually could run on less octane with that compression. 93 is perfect, no booster needed.
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PRIDEnJOY
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03-13-2011, 06:17 PM
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Senior Club Cobra Member
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Join Date: Jan 1999
Location: MARKSVILLE,LA.,,
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Quote:
Originally Posted by fordracing65
9.5 compression is fine on 93 octane, it actually could run on less octane with that compression. 93 is perfect, no booster needed.
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Since the mid 90's all I've put in my car is 93 octane pump gas........351-W, 10.3 to 1 compression, iron heads, no problems..............
David
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DAVID GAGNARD
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03-13-2011, 06:31 PM
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CC Member
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Join Date: Jun 2008
Location: Chester Springs,
PA
Cobra Make, Engine: Kirkham 289 FIA #690, FRPP 427 Boss engine
Posts: 764
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Actually, 91 should be fine with that set up.
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Kirkham #690 289 FIA
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03-13-2011, 06:40 PM
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Senior Club Cobra Member
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Join Date: Jan 1999
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Quote:
Originally Posted by mreid
Actually, 91 should be fine with that set up.
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At the stated HP level,I'm assuming aluminum heads, if so, easily do it on 91 octane and most likey have no problems with 89 octane pump gas.....
David
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DAVID GAGNARD
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03-13-2011, 06:58 PM
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CC Member
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Join Date: Mar 2011
Cobra Make, Engine: #6101 streetbeast Ingelese stack EFI 351w/t-5 9" 4link 3.55
Posts: 277
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thanks guys!!
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03-13-2011, 11:01 PM
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Join Date: Sep 2009
Location: Camarillo,
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Cobra Make, Engine: SPF #2608, Roush 427SR T-W
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David, at the same compression ratio do aluminum heads require less octane than factory type iron heads?
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03-14-2011, 04:44 AM
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CC Member
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Join Date: Dec 2001
Location: Castalia,
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Cobra Make, Engine: EM cobra, 450 inch sbc running a best ET of 9.14..so far..ALL MOTOR...approx 800 horse.............ERA with 482 FE..All Aluminum Engine
Posts: 1,395
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Aluminum heads run cooler than iron heads, thus you can usually run one point more compression. Looking at it in reverse, I guess you could say they require less octane.
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Jack
XSSIVE .....
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03-14-2011, 06:15 AM
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CC Member
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Join Date: Feb 2003
Location: Puyallup Wa.,
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Cobra Make, Engine: Superformance Cobra #1628, Coast Performance Stroker 427W Ford 520HP/535FT.TQ, Blue with white stripes
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Depending on how aggressive your timing is set, you just might have to retard the timing if it starts to knock.
Jake
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03-14-2011, 06:58 AM
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Me
Cobra Make, Engine:
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You do not need it unless you have too much timing in the motor.We have 91 octane and my 10:1 460 does just fine.Additives will do nothing for adding power.
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03-14-2011, 01:27 PM
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Senior Club Cobra Member
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Join Date: Mar 2001
Location: Southern Connecticut,
CT
Cobra Make, Engine: SPF - 351W, 944 non-turbo
Posts: 2,105
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Higher octane rated gasolines burn more slowly. Therefore using more octane than you require may actually decrease your HP. Using lower octane than you need will damage your engine.
Bob
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03-21-2011, 08:28 PM
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Super Moderator
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Join Date: May 2001
Location: Fresno,
CA
Cobra Make, Engine: KMP 184/482ci Shelby
Posts: 14,445
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......................................
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Jamo
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03-21-2011, 10:01 PM
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CC Member
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Join Date: Feb 2007
Location: Colorado Springs,
CO
Cobra Make, Engine: Backdraft, supercharged Coyote
Posts: 2,444
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Octane is predominantly used to control detonation. Detonation comes when the pressure or tempe is high enough to ignite the mixture before the spark plug can.
9:1 comprssion is pretty low, even at 1,000' ASL. The SBF generally can't make use of more than 35* or so of timing. Even with iron heads, the only time you might have problems is when it's really getting hot; like 220*+.
What's your cylinder pressure? Have you done a compression test? If you have a big cam you might be giving away a lot of power. 9:1 is stock engine range.
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