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What would be the highest compression ratio you would want to run on the street. Being able to run on pump gas...
 

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depending on where you live could depend on what kind of gas is available. Here in San Diego we have 92 octain as premium ($1.55 gal.) so when my engine was built they recamended 9.5:1 for me.

So what kind of octain are you guys getting for how much?
 

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From the pumps that I have been to, 1.27 for 91 Octane Premium, around Reno, NV. I have heard a rumor that there is a station in town that has high octane for older cars. I have yet to go check it out. I hope it is true! It would beat buying octane boosters!
Later-
Matt
 

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Do yourself a favor,keep the static compression ratio in the range of 8.5:1 to 9:1.This will allow you to use a cheaper gas and enjoy care free motoring.As the other gentlemen mentioned,when compression ratios climb above the 9.5:1 ratios,it takes a considerable amount of tweaking to make the engine operate trouble free.The gains from a usable increase of compression ratio will be minimal..Livermore Dave.
 

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I kinda think that 8.5 to 1 would suck
then again I am in AZ so premium is running like 1.15

although 8.5 to 9 to 1 will let you use lower octane gas it will also not make as much power so you will use more gas

your decision, use more or pay a little more for the good stuff
 

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While we're on the subject, Does anyone know what the stock compression should be on a 1989 5.0 HO motor?
I'm putting mine back together soon and I guess that's something I probably should know...
 

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Well, I will be runnung 11.3:1 in my 466. Should run OK on pump gas with polished chambers and a large cam. Good heads make a big difference with detonation and compression issues.

Greg P
 

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It all depends upon the rest of the engine combination, the cooling system, head material, plugs, A/F ratio, etc...

But, larger cams bleed off more cylinder pressure, so the larger the cam, the higher the compression ratio needs to be.

With a near-stock cam, anything over 9 to 1 is pushing things. With a hot 7000rpm cam, 11:1 is not out of the question. All this is with iron heads.

Aluminum heads can stand about another half point.

Good Luck!
 

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On 2001-12-21 20:35, SawBones25 wrote:
While we're on the subject, Does anyone know what the stock compression should be on a 1989 5.0 HO motor?
I'm putting mine back together soon and I guess that's something I probably should know...
I belivie it is somewhere around 9:1
 

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Lordviper,it all depends on your camshaft with it's overlap!! You may get 220 psi cranking compression,and running be at 150 psi!! IT'S ALL IN YOUR CAMSHAFT!!!
 

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I've got aussie iron heads on my cleveland which give around 10.5 to 10.75:1 compression. It runs fine on 92-93 octane pump gas, but i've got a pretty big cam also.
 

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I am running 11.5:1 compression with a 600+ lift cam topped with a tunnel ram with 2 600's on a 351w. It is in a 68 mustang which I drive 45 min. to work a couple times a week and I get 18 miles to the gallon. I run 92 octane with no problems.
 
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