i was curious what octane you mix your 110 with? Ive built new motor over the winter and ended up with about the same compresion..

That is a great calculator. Thanks for sharing. I had the thought of contacting tech support @ VP race fuels today. I asked him how to accurately mix different octane fuels. His answer was as simple as my first post. In a mix of different octane fuels, the octane will be an average of the fuels mixed, by percentage of mix. Meaning, 5 gallons of 90 mixed with 5 gallons of 100, produces 10 gallons of 95. The equation is simple to do. Now that by u boy has added the neat calculator, its even easier. The problem is it takes a good amount of race gas to raise the octane of pump gas. In my case, I have an 80 gallon tank. It would take 15 gallons of 100 octane , to raise 65 gallons of 89, to 91. Not easy for me to do, when I cant fuel up at my marina for insurance reasons. I was hoping that it would take alot less race gas to bring up the pump gas. I am sure I could get away with adding a few gallons at the yard, but 15 may be a bit much.
My friend who is in the same situation as me, came across a stroke of luck today. He found that a local fuel dock, will be getting a shipment of 91 delivered tomorrow. If it sells enough, he will keep getting more. If that is the case, all our problems are solved. Maybe I should hire a sign plane to fly by the ocean beaches advertising for this guy. May as well start here... Anyone looking for 91 in the area of Jones Beach, head over to Scotty's in Point Lookout..

I run 8.9 to 1 comp & 36 deg timing with iron heads. I use 89 octain and have not had any issues. Keep your fuel fresh and only buy what you will use in a couple of weeks. I learned my lesson with old E10 fuel, I took out the tops of my rod berrings.

interesting thread, I just bought 500 gal. of 90 octane premium fuel with no ethanol. my engines call for 93, my fuel dist. told me because this fuel has no ethanol is should be fine. I have some avgas was thinking of mixing some in, what do you fuel guys think? should I add some avgas or is the high test 90 good?

as most of you know I operate a fuel distributorship and we make and blend our own race gas. I will be more than happy to attempt answering your questions. If it were me I would mix mixed race gas instead of just av gas. It will take more av gas ratio than race gas. Your beat option is to buy some higher grade race gas and mix it. That way you could raise the octane level with smaller quantities of fuel

So you think I should add some race gas to it? I like the idea of what I have now having no ethanol or additives, less water issues etc. Does not having the ethanol help with detonation? Can I get by with the 90 as it is? Hard to get good race fuel around here, can maybe get Torco or Cam2 somewhere or have to drive an hour to the refinery and by a 55gal drum of the good stuff.

The anchorage in lindenhurst has good gas !! I think they even have 100 rite at the dock .

I think you answered your own question with the knock sensor set up. Everything else is just a guess....or expensive.

It should only be necessary to install a knock sensor on one engine. As a base like, test with 89 as is. If you detect any knock, start dialing the timing back. We see minimal HP change in the timing on 9.3 CR and iron heads....maybe 10 HP between 34-38 degrees. If you still have detonation and you aren't willing to give up the HP, you can blend in 110 race fuel in five gal increments until you like the answer.

Share the results and everyone on OSO that reads will all buy you a beer

I run 93 and only add the 110 to the fuel that sat in the tank all winter. I put about 5 gallons to the 60 gallon tank. After that I just run 93 and have had no problems. I did snap a crank last summer and have not pulled the motor yet

I found this interesting write up on octane. You guys thinking of avgas, beware, page 2 says it may contain lead. Not that many of us, if any, run cat converters. Its just good info to know.

http://auto.howstuffworks.com/fuel-e...question90.htm

zzsupeboat,
Didnt know the anchorage has good fuel. Thanks for the info.