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Max compression with regular gas?

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Old Dec 25, 2014 | 11:09 PM
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Max compression with regular gas?

On a 400, how high of compression could you have and still run regular, not premium fuel?
 
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Old Dec 25, 2014 | 11:20 PM
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. Depends on cam size/spec.s, combustion chamber and piston prep., ignition curve/advance, thermostat temp., cooling capacity, usual workload, and engine quench distance... etc...


. Usually 9:1 or slightly more... lots of variables... I'd aim for 9 for efficiency's sake and do what's necessary to make it work if sticking with 87 regular... avoid the actual 7's of '72 and later engines...
 
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Old Dec 25, 2014 | 11:37 PM
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That's where I'm having trouble. This is going on a 79' 2wd that will be used as a daily driver and to occasionally pull a trailer (around 3-5 thousand pounds, 3-4 times per year) I want a strong motor that can run on the cheap gas. I'll be running an Edelbrock 2171 intake with a street demon 625 carb, just haven't decided exactly how I want to build the motor from here.
 
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Old Dec 26, 2014 | 12:47 AM
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. Even Premium is cheap gas now... $1.79 here today for Regular...


. 400's came with 9:1 for the first year... 1971...
 
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Old Dec 26, 2014 | 07:07 AM
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Another thing it depends on is the material of the heads. Aluminum will let you have another point or so of compression.
 
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Old Dec 27, 2014 | 12:14 PM
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Agree with all the above......

Back in the day of when lower octane 1st hit, Crower had a series of grinds that would allow up to a 11:1 CR and not exceed 150 psi.....of course with all the right parts.......
 
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Old Jan 1, 2015 | 08:05 AM
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. Geez... gas still dropping here in the new year... $1.59 now... gotta get that 400 built so I can put some serious amount of gas through it...
 
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Old Jan 1, 2015 | 08:23 AM
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Originally Posted by BuzzLOL
. Geez... gas still dropping here in the new year... $1.59 now... gotta get that 400 built so I can put some serious amount of gas through it...
Amen, brother! My 400 is begging for life!
 
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I'm running about 8.5 on my 2v cleveland. I've got a set of aussie heads that would bring me up to 10:1.
 
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