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Author Topic:   Fuel Octane VS. Compression Ratio
GnarlyCar
Dirt Newbie

posted August 11, 2002 12:39 PM
OK, guys..Comin outta left field here. Haven't been in this forum for a LONG time cuz I sold one of my cars and have spent the race season assembling the other for my kid to run as a B-Mod. What's a B-Mod? Well, it's a modified that runs a 9.5:1 stock-everything-engine, 'glide with a converter, and a Holley 4412 on gas. We're getting close to gettin it on the track and I started remembering when I ran street stocks 7 or 8 years ago, and having seen a chart in one of the race mags that said what octane you should run with whatever compression ratio you have. I have to think a 9.5:1 motor should be able to run pretty well on pump premium, but I have no idea where I might look for that info. Any suggestions, ideas, or info would be greatly appreciated.
Also..anyone with any ideas what the chassis is gonna do when it goes from 550hp to 350hp, you'r input could come in handy as well. The car's a 4-bar, floated brakes on both sides, with a lift bar. The car worked very well when it was run as a 550hp modified 2 years back, and I have some ideas what I want to do with the chassis to compensate for the HP difference, but some fresh unput's always welcome.
Thanks,
Matt

uforacing51
Dirt Freak

Total posts: 240
posted August 11, 2002 11:40 PM
I would think that most any engine manufacturer would be able to help you out with a question like that, or vp racing fuels or turbo blue is a sponser of WISSOTA, maybe they would have answers for you. I run the vp red in a mostly stock 10.5 to 1 pure stock engine and it really kicks things up a notch. But I can offer no real science to my answer just seat of the pants stuff. As far as the chassies goes, I would assume that taking some spring out to compensate for the lesser horsepower makes sense but, again, I have no r&d to back it up.

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