pump gas ??HIGH COMPRETIOM

James Bond

Dragway Regular
Dec 26, 2005
1,359
0
0
Earth
i'm no engine expert, but i believe there are more factors than just compression. i'm thinking rod length, piston shape, and chamber shape will need to part of the equation as well..
 

DFWMalibu

Dragway Regular
Dec 15, 2006
999
0
0
Dallas,Tx
yeah also if there are any sharp edges in the cylinder or on the pistons it will create hot spots that will cause detonation.....

Chris K.
 
A

Anonymous

Guest
I wouldn't want to run straight pump gas on anything over 10.5:1, but that's just me.
 

Blackwizard22

Frequent Racer
Feb 26, 2007
453
0
0
NJ
You can run pump gas on a 13:1 motor that has all the timing taken out of it.

For street you wouldn't want more than 10.5:1 and that is with a good cylinder head.

You can run a little more compression with pump gas with a vortec head because they like less timing that the old school stuff. Aluminum heads will get you a bit more of a buffer against detonation as well.

You will also want to make sure you have the right heat range with your plugs.
 
A

Anonymous

Guest
I have a 383 that's 11.5.1 with a good head on it and run pump gas I do have a little timing taking out of it but car still runs hard and strong with no spark knock or anything i even dyno'd it that way made a little over 600hp to the tires. So it all depends on your combination.. 8)
 

Jordan81

Pro Stocker
Feb 10, 2004
1,774
0
0
wichita, ks
heads, pistons, cam... none of that matters. how much money you got? thats what matters. if your not working with much and iron heads i would go 11.1 at the max. alum heads you can usualy get 1 more point of compression out of
 

ProJunk

Dragway Regular
Sep 12, 2006
902
0
0
Glendale, AZ
The closing point of the intake valve has some of the largest influence on octance tolerance vs. compression, as well as combustion chamber shape and quench area. The later the intake valve closes, the less cylinder pressure the engine will develop, and the more tolerant of increased static compression ratio the engine will be. For a general rule of thumb, engines with cast iron heads will usually handle up to 10:1 on 91 octane, and engines with aluminum heads will usually handle up to 11:1. There are more extreme pump gas combinations out there, but this is a good general rule to follow. Cranking compression is a little bit more accurate determining factor for pump gas use. 170-180 psi of cranking compression is about the max for iron heads, and 200 psi for aluminum heads.
 

big-angry-hillbilly

Amateur Racer
Mar 28, 2009
107
0
0
Windsor, Ontario, Canada
ProJunk said:
The closing point of the intake valve has some of the largest influence on octance tolerance vs. compression, as well as combustion chamber shape and quench area. The later the intake valve closes, the less cylinder pressure the engine will develop, and the more tolerant of increased static compression ratio the engine will be. For a general rule of thumb, engines with cast iron heads will usually handle up to 10:1 on 91 octane, and engines with aluminum heads will usually handle up to 11:1. There are more extreme pump gas combinations out there, but this is a good general rule to follow. Cranking compression is a little bit more accurate determining factor for pump gas use. 170-180 psi of cranking compression is about the max for iron heads, and 200 psi for aluminum heads.

^^^^^^^^^ We have a winner!

Thanks for saving me having to type all that :D
 

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