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Old 08-18-2010, 04:40 PM
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too much compression

The debate continues... How much compression is too much compression for pump gas on a Iron headed Small block chevy with a 276/284 duration cam??? I have 10.7:1 with no detonation and my buddy wants to go 11:1.. I think it's too much...

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Old 08-18-2010, 05:01 PM
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You can run on pump gas with 11.1 comp. I do it all the time you will have to properly adjust everything just like you would anyway but you can run on it. At-least 93 octane JMO. But i would say 11.1 is pushing the limit pretty close. IMHO.
I am sure someone will say no way but i know for a fact you can maybe not on all setups but for the most part you can. JMO You might want to through in some good additives every now and then but it will work. But it would probably perform better on a little better fuel though.

Cole

Last edited by eloc431962; 08-18-2010 at 05:07 PM.
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Old 08-18-2010, 05:14 PM
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With Iron heads??
We have 93 octane here and that's pretty much all we use anyway. A little more when we get fuel at the track..
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Old 08-18-2010, 05:16 PM
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Yes with Iron heads, I am running a set of 230 Dart Iron Eagle heads on my set-up does fine on pump gas.

Oh by the way which Iron Heads is your buddy going to be running anyway ?
Cole
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Old 08-18-2010, 05:23 PM
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11-1 is certainly right in the edge for something that isn't reverse cooled, fuel injected, and has knock sensors.

I've done it too, just like Cole. You can't do it with a cam that small if that is the advertised duration #'s that you posted, you need the @.050" duration numbers to be up near that, to get away with it. Chamber shape plays a part too, you can't do it with typical smogger heads
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Old 08-18-2010, 05:42 PM
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He has the World Sportsman II's with 200cc runners and they've been ground to 56cc chambers. The @ .050 duration numbers are 233/241 on the cam.
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Old 08-18-2010, 07:05 PM
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Quote:
Originally Posted by 19nova69
He has the World Sportsman II's with 200cc runners and they've been ground to 56cc chambers. The @ .050 duration numbers are 233/241 on the cam.
Not going to work, not enough duration, needs 246+ @ .050" on the intake side.
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Old 08-18-2010, 07:07 PM
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Quote:
Originally Posted by 19nova69
He has the World Sportsman II's with 200cc runners and they've been ground to 56cc chambers. The @ .050 duration numbers are 233/241 on the cam.

I take it he has the heads and wants to sell them to you and make your 10.7:1 motor 11:1.

1. you are really riding the edge now at 10.7.

2. the power gain if any will be minimal at best. A strong tail wind will make more difference.

3. Just a bit too much compression ratio is instantly way too much when detonation results. Kind of like tightening the lid further and further on a pipe bomb.

All is well right up to the point when it goes BANG!!!!
Then your friends and all the dynamic cr theorists /experts scatter.

4. There are many many critical variables that don;t stay constant., that you cannot control.

www.ramairbox.com Make the engine process more cooler, dense, air.
Does not need better gas. No increased risk of detonation. More real power gain.

Easy to install on a 1969 Nova.

Last edited by F-BIRD'88; 08-18-2010 at 07:23 PM.
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Old 08-18-2010, 08:18 PM
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Quote:
Originally Posted by F-BIRD'88
I take it he has the heads and wants to sell them to you and make your 10.7:1 motor 11:1.


www.ramairbox.com Make the engine process more cooler, dense, air.


Easy to install on a 1969 Nova.
NO, I have my my own similar heads but mine are 64cc's. My motor is staying the same, it works well!!!

I like that ram air box, pretty cool, but I think it would defeat the cowl hood I got, or I could have the ducts face the opening.... hmmmm
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Old 08-19-2010, 05:39 PM
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Quote:
Originally Posted by 19nova69
NO, I have my my own similar heads but mine are 64cc's. My motor is staying the same, it works well!!!

I like that ram air box, pretty cool, but I think it would defeat the cowl hood I got, or I could have the ducts face the opening.... hmmmm
The ram air will out perform the cowl hood. Pick up the air from the front of the car. It works better than any cowl hood will. The cowl hood is for clearance room only.
If you can't see it, don't bother.
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