Rapid Robert
Well-Known Member
63 dart 360 2bbl 904 8&3/4. 235/75/15 street tires. 3/8 mile high banked ruff dirt track. hobby stock class (street stock). 6K rev limiter. thank you for your time. RR
are 5:57 gears too deep?
- Thread starter Rapid Robert
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Maybe not. When modified raced cedarburg where I grew up, they raced 6:66 0n 1/4 mile clay.
My 49 Ford 8N tractor has 6.66 gears. It's goin to hell. lol
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What gear ratio are you running now and do you hit the rev limiter now?
Professor Fate
Push the button, Max...
Second gear nets you just over 60 mph if you're bouncing the engine off the rev limiter, 90ish in third. I doubt you'll be seeing 6K very often with a 360/2bbl.
Don't know what they let you run for a cam in HobbyStock, but a stockish 360-2 makes peak torque around 2000 rpm, so keep that in mind.
Don't know what they let you run for a cam in HobbyStock, but a stockish 360-2 makes peak torque around 2000 rpm, so keep that in mind.
1WildRT
Well-Known Member
Tire is 28.7 tall
What is max MPH
Running in Second or Drive?
Realistically your 360 2bbl will be all done around 52-5300
What is max MPH
Running in Second or Drive?
Realistically your 360 2bbl will be all done around 52-5300
Rapid Robert
Well-Known Member
excellent info! I will check out that site. It hasn't ran yet & I have the 5:57's on hand. running in drive. we can run any non roller cam. EDIT 9-1 CR. genuine EQ magnum heads.
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Rapid Robert
Well-Known Member
good info. Yeah I'll have to get out there & running to get some figures. I'm just worried that the 5:57's might be too deep to start with. RR
;57
;57
1WildRT
Well-Known Member
As previously mentioned 5.57 with a 28.7" tire in drive at 6000 rpm's not allowing for convertor slip should be 92 MPH
Rapid Robert
Well-Known Member
92 MPH X 5.57 x 336 divided by tire dia =5999 RPM
5999 RPM X28.7 divided by 92 MPH X 336 = 5.56 gear
5999 RPM X28.7 divided by 92 MPH X 336 = 5.56 gear
okay... let's try a different approach. what mph do you need to run to be in the front-middle of the pack?
Professor Fate
Push the button, Max...
What cam are you running? Need to know your approximate torque curve to get real numbers for your gears, and whether the 6K rev limiter is even going to be a factor.
But for the sake of discussion, let's plug some general numbers into this.
If your engine can safely run the 6K number (if not, the rear gear may need to be decreased numerically, and based more off of your torque numbers than rpm) consistently by the end of the straights, then something in the ballpark of a 6 to 6.30 final drive would be where you want to be. Your 904 would give you 5.56 in third or 8.06 in second, neither of which is considered ideal- but running it in third would be best with your existing gears. Optimal would be a set of 4.10/4.11 gears that would get you a final drive right at 6 if you run in second (1.45:1 in your 904).
Since you're just starting, get the chassis figured out before you start pursuing every last HP- tie your subframes (I'll assume that's done, since you undoubtably have a cage), get about 100# of ballast at the left rear (even if it puts you over the minimum weight) and the heaviest shocks you can lay your hands on.
Disclaimer: my dirt track days ended almost 40 years ago, but the basics are still valid. Not knowing your track rules, i.e. competition/stock shock rules, .500 lift cam rules, header/manifold rule, etc. can and will affect a lot of things.
But for the sake of discussion, let's plug some general numbers into this.
If your engine can safely run the 6K number (if not, the rear gear may need to be decreased numerically, and based more off of your torque numbers than rpm) consistently by the end of the straights, then something in the ballpark of a 6 to 6.30 final drive would be where you want to be. Your 904 would give you 5.56 in third or 8.06 in second, neither of which is considered ideal- but running it in third would be best with your existing gears. Optimal would be a set of 4.10/4.11 gears that would get you a final drive right at 6 if you run in second (1.45:1 in your 904).
Since you're just starting, get the chassis figured out before you start pursuing every last HP- tie your subframes (I'll assume that's done, since you undoubtably have a cage), get about 100# of ballast at the left rear (even if it puts you over the minimum weight) and the heaviest shocks you can lay your hands on.
Disclaimer: my dirt track days ended almost 40 years ago, but the basics are still valid. Not knowing your track rules, i.e. competition/stock shock rules, .500 lift cam rules, header/manifold rule, etc. can and will affect a lot of things.
I sent you the gear chart for the class you're running in and the tracks near you in Nebraska. It has gear recommendations for open and crate options. If it's not on the chart tell me which track you need the gear recommendation for and I'll find it for you. If you didn't look at it here it is again. Why are running a 6k rev limiter? Your rules allow 7000 RPM on an open motor.
Rapid Robert
Well-Known Member
92b yes I saw the chart, thank you very much & it tells me that my 5:57's will be just fine which was surprising. & I reread the rules & you are correct my motor can use a 7K rev limiter
Which track are you racing at?
Rapid Robert
Well-Known Member
eagle nebraska
Eagle takes a 6.50 or a 6.66 gear for an open motor. You want to run a 5.57?
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Rapid Robert
Well-Known Member
yes, its what I have at the moment.
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