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Discussion Starter #1
My 686 Raptor will be done in about a week or so and my mech said I should atleast run a mix. He suggested Sunoco but didnt say what octane. What other brand of Race fuel should I consider and which type. Also where do most of you get your fuel from? Thanks
 

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Where are you located? I sell Nutec race fuels and they have a new mix that will out :tup: HP any other Oxygenated fuel on the market, if you would like to give a try Pm me with info..
Or i can forward you with the nation wide distributer...
 

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Discussion Starter #3
I am on the East Coast in Virginia.
 

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Hey neighbor! You can get VP race fuel in Manassas at C&C Auto Performance

C AND C AUTO PERFORMANCE
8081 Centerville Rd.
Manassas, VA 20111
(703) 368-7878

What piston in your 686? VP Red ran good in my 13:1 686, I never mixed it down. Depending on your compression, you might get away with 50:50 93 octane and VP Red.

Stay away from C12 for a 4 stroke, I hear it doesn't burn right.
 

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What is wrong with vp c12? I use it and havent had any problems. I am just asking because i havent herd anything about it.

here is what vp has to say about c12

C12
The best all around racing fuel made. Recommended for CRs below 15:1, satisfying the needs of 75% of today's race engines. One of the winningest fuels in racing history, including Modified Tour, GNN, D.I.R.T., Indy Lights, NHRA, AMA as well as other local and national championships across the U.S. and around the world.

• Color: Green
• Motor Octane: 108
• Specific gravity: .717 at 60° F

Info on there other fuels
http://www.vpracingfuels.com/vp_01_fuels.html?mgiToken=0C15B7C8AB5E97F908

I have thought about trying there vp 110?
 

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Discussion Starter #7
My piston is 11:1. I was planning on mixing.
 

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i mix to about 95-96 octane on sunoco....... runs great....thats on an 11:1
 

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I've been told that C12 doesn't like to burn at higher rpm in a 4 stroke? Heard it from two different sources so there may be something to it. When I dyno'd my Raptor at Aledo on C12, the A/F ratio went pig rich after 6k rpm. I was running smaller mains than a similar built Raptor and his EGT temp was 100 degrees higher than mine. Only difference between our builds was compression and fuel.

When I had a high compression 686, I had a heck of a time with the stock carbs. Nobody had figured out all the areas the stock carbs need to be tweaked to feed a built 686. At first, I ran VP Red. The idle circuit kept flooding but the top end was excellent. After fooling around with the stock carbs for a while, I bought a set of 35mm FCRs. Somewhere between testing stock carb mods and the 35mm FCRs, I switched from VP Red to C12. After I got the 35mm FCRs "tuned", I didn't think they had as good a top end as my modified stockers. After the dyno run and EGT comparison at Aledo, I think the C12 made the FCRs feel not as strong on top.

As soon as I get some motor parts back from the polisher, I'm going to try C14 and mix it down with 93 octane. The EGT will tell the truth, if the temps jump up then it was the C12 for sure.
 
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