enginehistory.org

[jschauer]

Back in the '60s, I heard a story that the Doolittle B-25s had a carburetion mod done to them. Another story I heard from a different source was that the B-25s used a much higher octane of fuel so as to get a higher horsepower out of the engines for takeoff. Anyone ever hear of this?

[wpearce]

If I remember correctly from Doolittle's biography, they used 100 octane fuel and the carbs were adjusted/bench-checked at Eglin AFB in FL. Doolittle did not want anyone touching the carbs after that but one plane had its carbs adjusted while in Alameda (CA) and it never ran quite right afterward (rougher and higher fuel consumption).
_________________
Bill Pearce

www.oldmachinepress.com

[jschauer]

I remember the carbs being readjusted, but could it have been to use a special higher octane fuel? Higher than 100/130 octane.

[wpearce]

I really do not know. Doolittle may not have known or not remembered or just not mentioned the extent of modifications to the carbs in his book. Since 100 octane was nothing new in 1942, there could have been a higher PN fuel used aboard the Hornet. Several times the book mentioned having 100 octane shipped to China but in my quick search, I do not see anything about what fuel was used on the ship.

It should be remembered the Doolittle worked for Shell and was very involved with the development, manufacture, and adoption of 100 octane fuel. It is conceivable he could have had higher PN fuel for the mission. But since the carbs were adjusted in FL and not touched after that, I would think that whatever fuel was used on the mission was the same used to ferry the aircraft to CA.

Given Doolittle's involvement and knowledge of fuel as well as the mentioning of 100 octane in China, I would think he would have mentioned if there were a higher PN fuel used on the mission. But that is pure speculation on my part.
_________________
Bill Pearce

www.oldmachinepress.com