117 octane fuel for a Jd G

If a natural aspirated tractor engine won't operate without detonation on 100LL. The combination of cam, mechanical compression ratio and combustion chamber is wrong.
High compression does not build power, it's the high expansion ratio even with extra cam timing that makes power.
It takes power to compress the air/fuel mixture which is #1 wasted as heat. #2 the engine makes power from expanding gasses. What is going to expand more? a cool 200F air/fuel mixture or a 450F air/fuel mixture?
Anybody ever wonder why the power increases from more "compression" is not linear?
 

Bowser - that must be some kind of "G"....

I have a Rockett Brand racing fuel brochure (2004) that lists 118 Minmum Octane (R+M)/2. Typical application would be for turbocharged, supercharged, nitrous oxide and high compression. I would think at 118 octane, if that does not run your G, you may have another problem.
 
In the real world, I have seen a 15 to 1 355 Ford Na. Engine make 850 HP. They can't make this power at 7.5 to 1 maybe 350 at most. Last tractor put together got it as close to 15 to 1 as possible. A little over 200 in. 85 plus HP. 2600 rpm. 4 cyl. 108 gas.:) Vic
 
We buy from our local speed shop. Also most Fuel jobbers can order by the barrel. Guys look on super Chevy danger mouse. Has the effect of compression on power. 10 to 1 to 12 to 1 45 HP on 91octane. Can't remember increase on 105 But substancil. We have needed a good discussion on here. Vic
 
VP Racing fuels makes one called Q16, it's 116 octane R+M/2 & is highly oxygenated (not alcohol) & is supposed to be excellent for big bore engines. They also have C16 which is non-oxygenated. The right fuel for your specific engine combination can easily show a 10% power gain v.s. One that just gets the job done. It's incredible.
 
(quoted from post at 22:37:36 12/24/14) Any idea who sells 117 octane fuel
If you're looking for a research octane number of 117, that isn't hard to find. If you're looking for motor octane of 117, choices are limited. I don't use Sunoco racing fuel at this time, but I believe they still have a 118 MON fuel for big inch engines

If you're looking, for a local dealer, the mfg will be glad to give you names of dealers in your area. There are a few other racing fuels available, but the most commonly available are VP or Sunoco. My buddies the drag racers experiment with different fuel brands looking for every single HP.

What quickly became obvious to me on these big cubic inch/cylinder engines with less than optimum combustion chambers is they like high octane gas. Without it, at lower RPM's with low air velocity and not-so-great fuel atomization, they knock. Big octane numbers could well be a crutch for mediocre combustion chambers, but we need to do what it takes.

Our local VP dealer is my neighbor and he does sell Q16, 116 MON (120+RON), to some of the area pullers. I've found that VP Late Model Plus, 113 MON, does not detonate in my JD. For our circle track racing engines, I've not had any problems with CR up to 16:1 using the VP Late Model Plus. But then again, the carburetor, intake, ports, and combustion chambers are not a 60 yr old design.

Unsolicited advice...For infrequent use, when gasoline is not returned to a sealed container, stay away from oxygenated fuels. They are not stable, dyno results for fresh out of the can are not what is seen at the track when the gas has been exposed to ambient conditions for a week or two in a vehicle gas tank or fuel cell. Key ingredients break down or evaporate and fuel quality is not the same.
 

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