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Whats your compression ratio?
Just interested in what compression ratios some of you are running in your engine. I have been calling a few places, looking for pistons, and was told by someone that 9.5:1 is about MAX for a street engine- which just happened to be the only thing he had available for my particular application.
So, what compression ratio are you running, and what is your opinion on the highest compression ratio for a street engine with todays fuel? Greg *edit* FWIW- I plan on going with the Edelbrock aluminum heads (72cc) |
I'm running 10.25 to 1 with aluminum heads. 9.5 to 1 with iron heads or 10.25 to 1 with aluminum is about as high you can go and still run pump gas.
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Hi Greg,
I am going to have right at 10.0 to 1 with my FE and Ededl heads. I know I could push it but I don't need the max. I want to be able to run on pump gas. I agree that 9.5 is just about max with iron heads. Later, Byron |
I am running 10.5 (I think its more like 10.8 based on what I have been told - not really a gear head) on 93 octane. Is 93 what you are calling pump gas or do you guys mean that because I am over 10.25 that I need to run race fuel?
James |
It all depends on how hard you want to run. I have 10.5:1 with iron heads and get by with 91 octane. If I was going to run hard 93 octane or higher would be in the car. Having said that, a guy I really respect because of his knowledge and background said 9.5:1 is the max he could recommend for 91 octane.
John |
All we can get here seems to be 91. There are a couple of stations around the metropolitan area that has 93 but they are not at all convenient. By the way, here is Indep Mo.
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Was 12.5 to 1, iron heads, NIGHTMARE on the street, loved it on the track with race gas! Rebuilt, went with 9.6, iron heads, NICE, and STILL darn near as fast as it was before!
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10.1 to 1 with aluminum heads ,351 stoked to 402. I live at high alttitude 6000 ft. so 91 octane works great for me. It ran at sea level but complained a little(lumpy idle and such)probably needed some timing taken out. go big or ?10 to 1 is fine with alu heads.
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I'll be running 10.1 to 1 in the 427, KC is building for me. Aluminum heads, HR cam. I told Keith that I wanted it to run on pump gas, and that was what he recommended. We have 94 Octane here, so it should run just fine!:D Used to run 12.5 to 1 in my old Corvette. I had to run Vortex Octane Booster, though for that!
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Mild 351 with aluminum heads and 10.2:1 compression ratio.
With about 35 degrees total advance, it runs great on 89 octane (mid-grade). |
I'm running 10.0:1 on 93 octane with my 428 FE w/iron heads...should be fine with the Edelbrock Performer RPM intake manifold.
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I am at 10.5 and run either 105 or 112 race gas mixed with 91 pump gas. The cobra snarles like a rabid dog. I luv it!!
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10.5, alum heads, all in @ 38deg timing. 93 octane / use 2 gal of av (100LL) gas per 10 of ultra. Runs fine.
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5.0 EFI 10.9:1 with aluminum heads and 93 oct gas. I made about 18 pulls on dyno's in three years. And a thousand 6000 plus rpm shifts, no problems.
Dwight And about 18 runs down the Main Street of London.:) |
I'm runninig 11.5 to 1 with Dove alluminum heads. I buy the best pump gas available (ussually 91 sometimes 92 rarely 93) and add Octane Booster & Fuel Stabilizer concentrate additative by Manhattan Oil . A 4 fluid oz. bottle treats 60 gallons of gas at 1 increment per 5 gallons. It was recamended by the previous owner. If I could buy 93 it would be great but. I had more a problem with cam and lifters going flat. 14° of initial advance and 20° in the distributor.
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I am running a Keith Craft 427 Windsor. Dart iron block with aluminum heads. 10.5 to 1 compression and does just fine on Kalifornia krappy 91 octane.
Doug, SPC088 |
So it sounds like there is no hard and fast rule then. As I said, I am somewhere between the 10.5 and 10.8 numbers I have been told. Its an all aluminum Dart block 351W bored and stroked to 427 with aluminum (AFR 205) heads and I run 93 octane only. The 93 is at almost every station around here and alot have 100 race fuel, but I didn't think I needed it... so do I? What if I plan on running a dyno? If I run a road race I would put race fuel in for sure, as thats what its for... but just cruising with the occasional squirt of the loud pedal???
James |
On my 347 w/aluminum Edelbrock heads, I have a "static" compression of approx. 10.3:1 and on 91 Octane here in California. So far, it's been running great. I am going to see what happens when we start hitting 100deg. weather this summer; all the driving so far has been in moderate to cold temperatures since early October.
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I am running 10.8 with Aluminum heads. I use 93 octane, but in cool weather I can run 89 ok if I need to.
I also have very tight piston quench clearance which supposedly helps. |
10:1 and aluminum heads.
Have only run 93 octane in it, and no problems at 6,500 miles. Cheers! Dave |
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