BigDawg Posted October 26, 2003 Report Share Posted October 26, 2003 I was wondering if you have a 11:1 ratio can you run on pump gas? If not what is the highest ratio you can run and use pump gas. Quote Link to comment Share on other sites More sharing options...
Guest nevarmore Posted October 26, 2003 Report Share Posted October 26, 2003 My Lincoln had 10.5:1 (I think) from the factory and I drove it on 92 octane for as long as I had it. Fed it a bottle of booster when I was going on a long haul or a hot lap. EDIT: That number is from 1965 when it rolled off the line, 40 years and 138K have probably seen some leaks and bad seals lower the number. 1965 still had leaded fuel and slightly higher octane ratings IIRC. The car mags usually shoot for not more than 10:1 for pump gas, mostly for efficiency. I do NOT know what the upper limit is. Quote Link to comment Share on other sites More sharing options...
gillbot Posted October 26, 2003 Report Share Posted October 26, 2003 I believe the LS1 is stock 10.0to1 CR and it runs fine on pump gas. I believe many are running 11.xto1 on pump gas as well. Quote Link to comment Share on other sites More sharing options...
SamZman Posted October 26, 2003 Report Share Posted October 26, 2003 Do you have aluminum heads? That will make a difference. I have a friend that's ran 12:1 on pump gas w/ an LT1. If you don't have aluminum heads you should get by w/ pump gas at 11:1, but that may be right at the limit. Quote Link to comment Share on other sites More sharing options...
recklessOP Posted October 26, 2003 Report Share Posted October 26, 2003 depends on the head(s), cam(s), and a million other things. the 11:1 motor in my corvette ran fine on pump gas... Quote Link to comment Share on other sites More sharing options...
gillbot Posted October 26, 2003 Report Share Posted October 26, 2003 Originally posted by Four Wheel Drift: depends on the head(s), cam(s), and a million other things. the 11:1 motor in my corvette ran fine on pump gas... Agreed it depends on many factors but the standard seems to be scattered between 11.5 to 12.5 for max on pump gas. Quote Link to comment Share on other sites More sharing options...
recklessOP Posted October 26, 2003 Report Share Posted October 26, 2003 Originally posted by gillbot: Agreed it depends on many factors but the standard seems to be scattered between 11.5 to 12.5 for max on pump gas. that wouldn't surprise me with an LS1 or LT1. old school small blocks aren't as tolerant... it would help if we had more info on the motor in question... smile.gif Quote Link to comment Share on other sites More sharing options...
slow4now Posted October 26, 2003 Report Share Posted October 26, 2003 Timing has a lot to do with it. Quote Link to comment Share on other sites More sharing options...
desperado Posted October 27, 2003 Report Share Posted October 27, 2003 Originally posted by bigbabyjesus: Timing has a lot to do with it. He's right, newer motors with knock sensors will pull timing to get rid of the pinging that you experience from poor gas. If this is a computer EFI motor, you don't need to worry about it too much. But if it's a carbed motor with regular electronic ignition then it can be a problem. There are ways of dealing with it though, but some are better than others. First thing that you can do is get an MSD ignition box with variable timing, this puts the timing on a knob in the drivers compartment. If you get some pinging, back off the timing to get rid of it. Another cheaper way of doing it is to run a bit less initial timing, which is wat the timing is with the vacuum advance disconnected. Then bring the timing advance slower as the RPM's rise. This requires stiffer mechanical advance springs in the distributor, and get an adjustable vaccum advance unit to also customize the timing curve. And learn to either read spark plugs or buy a bore scope so that you can look at the heads of the pistons. There are distintictive marks that show up on the piston tops if you are experiencing detonation. And detonation is BAD. The other reason to do this is that a hot motor, with headers and flowmasters or what ever is typically loud, sometimes too loud to head the detonation occuring. There are also kits that put a knock sensor in the motor that was not originally equipt with them but it feeds a gauge, not an ignition computer to pull the timing out so you have to be aware taht its' occuring and get out of it before you screw up the motor. Quote Link to comment Share on other sites More sharing options...
BigDawg Posted October 27, 2003 Author Report Share Posted October 27, 2003 I have alluminum heads, and I intend on putting a bigger cam in my car, the one it there now has .049" of lift for intake and exshaust. Quote Link to comment Share on other sites More sharing options...
OGRE Posted October 28, 2003 Report Share Posted October 28, 2003 as said before, you may or may not have to retard timing a couple degrees. when people swap my 99+ head on 96-98 GT's teh CR goes up to 10.5:1 and typically run on premium gas and they are still able to add timing. Quote Link to comment Share on other sites More sharing options...
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