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ratio question: Car description-weight 2k,BBF 460 making 604HP,C6 ,9 inch,30inch diam wheels, Currently using 3.7 (posi) , turns 2700rpm at 60mph.. plan to go back to 3.5..(open)(2200rpm at 55), thinking maybe 3.3.. keep in mind i can't hook up 18 inch mickeys and always on the edge of going sideways. Question? how high a gear can i go in order to drop RPM for cruising and still feel quick and have punch off the line. Dyno shows 300hp at 3000RPM and 509 ft-lbs,,440hp at 4000rpm and 576ft-lbs,,all done at 6000 rpm .. thanks for your opinions.
 

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600hp with peak torque in the same neighborhood in a 2K vehicle is a gracious plenty. Not sure what it takes to keep something like that pointed in a safe direction, but how sorted out is the suspension?

Any way you can get away from the 3-speed and get into an OD transmission? Even with my scrawny 200 hp, that 2.84 first and 0.70 4th with lock up make a big difference. Got a buddy running 4:10 rear with OD trans and he loves it too.
 

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Agreed, if the higher rpm muscle car sound bothers you, go OD. There are a number of reasons dropping the ratio is a compromise, but a couple are that it's easier to break the tires loose once you get rolling (you do burnouts in 2nd or 3rd, right?) and the pedal is more sensitive to that line that it will break loose, while the acceleration control is reduced.

You won't see much difference from 3.70 to 3.50 (most folks only seem to "notice" with more than .25 change), but likewise the improvement in reducing muscle car rpm will be minimal as-well. OD and 3.70 gears would provide a cruise ratio of about 2.60:1 while keeping the low-rpm grunt and control. Many here claim it as the best mod they ever did.

If economy is part of your motivation, efficiency tuning will bring better results than gear up-change, which can actually make mileage worse depending on your cam and other factors. Be prepared to possibly lose some MPG if you up-gear, moving farther out of the engine's rpm "happy zone".
 

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Agreed, if the higher rpm muscle car sound bothers you, go OD. There are a number of reasons dropping the ratio is a compromise, but a couple are that it's easier to break the tires loose once you get rolling (you do burnouts in 2nd or 3rd, right?) and the pedal is more sensitive to that line that it will break loose, while the acceleration control is reduced.

You won't see much difference from 3.70 to 3.50 (most folks only seem to "notice" with more than .25 change), but likewise the improvement in reducing muscle car rpm will be minimal as-well. OD and 3.70 gears would provide a cruise ratio of about 2.60:1 while keeping the low-rpm grunt and control. Many here claim it as the best mod they ever did.

If economy is part of your motivation, efficiency tuning will bring better results than gear up-change, which can actually make mileage worse depending on your cam and other factors. Be prepared to possibly lose some MPG if you up-gear, moving farther out of the engine's rpm "happy zone".
Thank you Mercury and PSIG for your response, OD is certainly the most drivable option. I looked into the add on OD for a C6 and they are expensive. I'm using a summit calculator that determines RPM,speed,tire dia,ratio for a guide line. I agree 3.7 to 3.5 isn't much. The 2.6 ratio i believe is optimal, but with out OD and a 1 to 1 trani in 3rd the cam would be struggling to feed the cylinders smoothly. Comardo Racing did as i asked and built me a streetable cobrajet 460. It is now up to me to tame it for safe driving. I had to remove kick down for safety reasons. I'll try the 3.5 since i have one,. Next I'll start working down. The suspension is designed for this HP. Reality is I'm
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probably not moving more then 400 to 425 hp to rear wheels driving on the street. Its the torque and the driver that breaks the wheels loose. Sure be fun to have a modern 10 speed transmission. Thanks again,every bit of info helps.
 

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Currently using 3.7 (posi) , turns 2700rpm at 60mph.. plan to go back to 3.5..(open)(2200rpm at 55),
Using an open rear with 600hp will result in the embarrassing 'one wheel peel' at anything over 1/4 throttle. I'd definitely use some sort of (posi) with whichever gear you choose. My favorite is a 3.25 for the street, but with your tall 30" tires, 3.5 would work well. I wouldn't go any taller than a 3.25.
Good Luck
 

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Thank you Mercury and PSIG for your response, OD is certainly the most drivable option. I looked into the add on OD for a C6 and they are expensive. I'm using a summit calculator that determines RPM,speed,tire dia,ratio for a guide line. I agree 3.7 to 3.5 isn't much. The 2.6 ratio i believe is optimal, but with out OD and a 1 to 1 trani in 3rd the cam would be struggling to feed the cylinders smoothly. Comardo Racing did as i asked and built me a streetable cobrajet 460. It is now up to me to tame it for safe driving. I had to remove kick down for safety reasons. I'll try the 3.5 since i have one,. Next I'll start working down. The suspension is designed for this HP. Reality is I'm View attachment 168781 View attachment 168782 probably not moving more then 400 to 425 hp to rear wheels driving on the street. Its the torque and the driver that breaks the wheels loose. Sure be fun to have a modern 10 speed transmission. Thanks again,every bit of info helps.
Awesome car too. You might find a pretty good market for a well built C-6 and I think there are some shops that fit a beefed up 4r70w in a BBF E4OD case (or something like that) there is a way to get the OD and if you aren't really hooking up anyway, the transmission may never see the engine's peak torque.
 
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