F-head high altitude head?

[LarrBeard]

" ...back in the day they only had 70 or so octane.."

Check the octane rating on this overhaul plate from a German Overhaul Depot after WWII.

[bmorgil]

Yikes! 68 Octane... sounds like dishwater from the greasy spoon.

[gmwillys]

Fuel has come s long ways since then. I had a John Deere B that had a small gas tank to warm the engine up then you turned the main tank which was for distillate, (low grade fuel). The deuce and a half military trucks would run multi-fuel engines that could burn anything flammable.

[56willys]

56', I promise you I have seen more boy's passed on the track that didn't understand the basics, than I have seen those that did understand get passed. When you start where you are starting, things make a lot more sense when you jump into the advanced stuff. So many today want the answer not the process. You can rest assured the day will come when those who rush in with money and incompetence, watch from behind those who understand how the whole thing works from the very basics, finish in style. When you build your first Hot Rod, it will be a winner. Flossy is showing you how it all started.

I can agree, the journey is always the most fun. I can think of soo many examples, like I am into model trains and model cars. (Or used to be, lately jeeps have been taking time/money away from other hobbies) but I always think as I'm building a new train layout or model car, how much I want to see it finished. But when it's done the thing I truly enjoyed the most was the process of building it. I could care less about having it done, the real fun is building it.


Wow, 68 octane,. That's just a little different then the 110 my friend runs in his cars!!

That's why I was thinking higher comp. might be a good idea since now the lowest is 87. Although I don't think it will hurt anything in the motor to have higher octane.


I looked over my spare head and didn't find markings that match what gm found. The only thing similar was an 8.07. Backwards of what it should be. But after all it is a willys part! I did learn something new, so if I ever find a head for sale I can see what compression it is. So I appreciate the help!

[56willys]

Fuel has come s long ways since then. I had a John Deere B that had a small gas tank to warm the engine up then you turned the main tank which was for distillate, (low grade fuel). The deuce and a half military trucks would run multi-fuel engines that could burn anything flammable.

Oh yes, I always wanted an m35. It would look so cool with a willys pulled up into the bed. And yes, running it off of vegetable oil would be so neat! The only problem is the fact that it's the size of a house. But they are such cool trucks! That john deere is like a lot of antique tractors/hit and miss engines. That would start on gas to warm up then switch to kerosene for running . (Okay I might have the two backwards but it's something like that).

[gmwillys]

The building is half the fun. The other is the years of smiles you'll get from driving Flossy.

[LarrBeard]

"...Yikes! 68 Octane... sounds like dishwater from the greasy spoon...."

If I can trust my failing memory, in Germany during WWII, much gasoline was derived from coal, not crude oil. During the restoration period, local gasoline might still have been from coal stocks and could have had an octane rating about that number.

[gmwillys]

I am certain you are spot on Senior Chief. Cooking oil is a good fuel source if it is warmed up, but it makes everyone riding and passing by hungry for French fries.

[bmorgil]

Since we are going on an octane journey here, I like this chart. Notice how even though we "got the lead out" and octane ratings stabilized, compression ratios continued to climb. In fact some of the newer engines approach 11 to 1 compression on 87 octane fuel. This is a testament to the design of modern cylinder heads and combustion chambers. As the combustion efficiency goes up, the tendency to detonate goes down. We make some good motors these days.

https://www.energy.gov/eere/vehicles...asoline-octane

[LarrBeard]

There are several old airplanes flying today (Doc and FiFi, The SuperConnie and numerous B-17/24/25's) that can't fly above about 12,0000 feet because above that altitude they need boost on the engines and with "just 100-octane" fuel, they detonate and gag.

Although I don't understand the complete octane rating, WWII AvGas and fuel for the last generation of radial engine aircraft was rated as 113/130 octane. They were called "aromatic fuels" because the molecular structure looked more like perfume than conventional fuels.