Ron at Bonneville VP racing fuels brand is the gas available.
Anyone running for a gas record must use the VP gas. Example of the octane grades available C-16 has an octane rating of 116 for compression ratios up to 17.1.
The actual altitude at Bonneville is just over 4000 feet for a flathead that has a hard time breathing at sea level this of course is a big issue. I've read for every 1000 feet of altitude an engine can see a reduction in power of 15 percent.
When other factors are added in the density altitude gets even worse early morning at Bonneville the density altitude is just under 6000 feet. That's why the backup runs for a record at Bonneville are held early morning so our engine's have the the best air possible.
Here's one example and some details from the fastest run to date we made with our stock block Ford flathead
{Note stock block means we use the three exhaust ports on each side of the block as designed we do not add any other exhaust port}
Our flathead is 292 cubes we burn C-16 VP gas the car weight is well over 3000 pounds.
The density altitude just after 2 PM in the afternoon was over 7000 feet the Ford flathead engine turning 6100 RPM ran 219.8 MPH . To get a speed this fast burning gasoline takes horsepower lots of it we always run a block relief to help the combination to survive. Hopefully this information will help others in the future who may one day decide to try and do this crazy stuff some of us are doing.
Ronnieroadster