My 434" small block was broke in and tuned on a engine dyno using Crate 98 race gas. After all the tuning we pumped the fuel cell and emptied the carb bowls and poured in a can of pump 93. After bringing it up to temperature it made 30 more hp than the 98 did. I thought it was a fluke or something went wrong with the computer so we cooled it down and made another pull, again 30 more hp.
One dyno operator I talked to said some combos that can run on pump 93, will sometimes make more power than race gas. He didn't say why, but one thought I had was the oxygenation of the 10% ethanol (need to jet for it). My 10.3CR engine didn't vary more than 1-2 hp going from the dyno shop 112 race gas to my 93 pump gas I brought with we. We used a oxygen sensor in the exhaust to tune my carb. So in my case, the fuel was not the limiting factor (likely my unported 452 iron heads, LOL).
