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Author Topic:   Required Octane
Dirt Full Roller

Total posts: 68
posted March 11, 2003 09:55 AM
How do I figure out the required octane for my new engine? On my Grand National, there's a software program that measures knock. But on a race car turning 6500 rpm with an "open" exhaust, I'm not sure I can here the engine knock! I remember reading somewhere that any octane over what your engine really requires is wasting money and fuel burning efficiency. I'm figuring I need somewhere between premium and 100 octane, any help?

350 sbc, stock rods and stroke. 10.5:1 compression, un-ported vortec heads. 4412 through a super victor manifold with headers. .520" or so lift with 250 duration @ .050". 3100# car.


Dirt Freak

Total posts: 352
posted March 11, 2003 04:32 PM
i agree, though i think 100 will go to 12-1 probably buy 105 or so and mix it..

Dirt Maniac

Total posts: 135
posted March 11, 2003 06:13 PM
5 octane more than you need is a whole lot better than 1 less. I would not try to pin it down too close, cause you are right, you can not hear it. A circle track engine, if detonating, tends to operate in the detonation range for a much longer time than a street or drag car. Even minor detonation will take it's toll.

Dirt Freak

Total posts: 214
posted March 12, 2003 09:37 AM
I know that some Gas stations sell higher octane racing fuel. Do you know of any?

Dirt Freak

Total posts: 237
posted March 12, 2003 12:36 PM
I've got a motor very similar that I ran a whole year on mixed fuel. 3 gallons of Cam2, with 2 gallons pump premium. I figure it was about 105 octane.

Of course, with the cost of pump premium right now, you don't save much over the cost of straight racing gas...

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