my brother put some octane booster in my stock 400ex... is that gonna mess up anything i think he put about 8 cap fulls in maybe a 1/4 or a 1/5 of whats in the bottle please reply thanx

I've poored a complete bottle of 105 octane boost in my 300ex. It ran fine, i didnt notice anything really... i did roll it 8 times that day... but it still ran great.

Won't hurt anything unless you really overdo it, then it probably wouldn't start anyway. It certainly wouldn't help a stock engine.

The 400ex has relatively low compression, so while it won't hurt the engine, I also doubt it would help the power a noticeable amound. Maybe if you had a 11:1 piston you'd see a difference, but for the most part that octane booster stuff doesn't do much.

it wont hurt, but it wont help , either
only if the engine is modded, or head is shaved/machined will it be of any use

IT WONT HURT IT WHAT SO EVER,YOU SHOULD NOTICE A BIT MORE OVER REV(EVEN WITH A STOCK ENGINE).YOU COULD PUT AS MUCH AS YOU WANT IN AND IT WOULDN,T HURT-IT'S BETTER FOR IT.BUT IT WOULD ONLY HELP TO A CERTAIN POINT UNTIL YOU ADVANCE YOUR TIMING OR UP YOUR COMPRESSION SO IT'S JUST SPENT MONEY ONCE YOUR OCTANE READING EXCEEDS THE ENGINE'S REQUIRMENT FOR PRE IGNITION AND CONTROLED AND BURNING.

psst.. your caps-lock is on. :)

A friend trying putting aviation fuel in my 400EX at Glamis and said it did nothing for its performance. He runs aviation fuel in his highly modified LT500. I can't tell any difference between 92 and 87 octane myself.

except for the crapy gunk building up in your engine... Y do you think cars valves ping?

I believe it is because with lower than optimal octane fuel, or too much timing advance, the peak explosion inside the cylinder happens before the piston reaches TDC, which must cause the piston to slap around a little or something on the down-stroke.