octane?175psi compression

[action280]

what is the perfect fuel to use with 175 psi compression on a mercury 280 ROS? i just shaved the heads and got 175psi compression. i have used it with 93 octane with booster and it just worked good but i dont feel any difference in power or acceleration, same top speed also :( :confused:

[rock]

I think that 175psi with 93 octane is like playing with fire. You might get by with it once or twice but you WILL get burned. I would think 101-103 should make it live but at that cranking pressure I would use racing fuel only. Just an opinion.
Rock

[EFI25]

If you mix VP 110 or Sunoco 110 race gas 50/50 with 93 pump you will be okay at 175.

[action280]

I'LL use vp c10 this weekend as i'm almost sure it will be destroyed with 93 with octane booster but i've used it about 4 tanks now with no problems.what do you guys think about the no- power boost with the higher compression? :o

[78Vector]

I'd use 50/50 93 octane pump gas mixed with Aviation 100LL gasoline in it. 100LL Aviation fuel is actually 115 octane using the automotive pump gas method of octane.
If you want to run straight AV100LL, you would have to re-jet if carbed 2 numbers richer as AV 100LL is less dense than pump/race gas though.

AV100LL is MUCH cheaper (around $2.70/gal at most small airports) than ANY race gas that sells in my area starting at $4.59/gal for Turbo Blue 110 or Sunoco 110. AV gas is actually higher octane than "base" level race fuel.
VP C16 is a whole other ball game....near me that stuff is upwards of $8/gal !