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Old 05-25-2011, 08:46 AM
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drag racing help

why does my car quit pulling after the 1/8 i have a set of 4.11 gears and a set of 5.13 and im running comparable times in both the 1/8 and 1/4 mile im running 7.32 at 94 mph in the 1/8 and 11.50 in the 1/4 at 112 dont under stand whats goin on

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Old 05-25-2011, 08:54 AM
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Ran it across the 1/8 mile to 1/4 mile conversion chart, it says with a 7.32 1/8 mile time, you should be running a 11.51 with a 1, looks to me like it is pretty close
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Old 05-25-2011, 08:56 AM
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Looks pretty close to me, What do you have the timing set at for these runs ?



Cole
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Old 05-25-2011, 09:23 AM
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but im running almost exact same time and speed with both gear sets
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Old 05-25-2011, 02:27 PM
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what about rpm- I took a guess at 6500 with the 4.11 with the 5.13 you would be around 8,000rpm!!! that tells me you don't have enough engine for the 13's . a couple racing buddies are running in the 10.50 -4.56 gear shifting around 7200. what is your setup cam ,heads ,tire size , traction device, converter and what are your 60' times with either gear. I would use the 4.11's for common sense purpose. what is the weight of your car?
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Old 05-25-2011, 04:22 PM
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Quote:
Originally Posted by bsp92097
but im running almost exact same time and speed with both gear sets
Yep i know that, and as stated the 5.13s are to much for what you have IMHO. And what type car are you running anyway what size rear tires ?
What engine and trans and what are the specs of the engine and what converter are you running also?

Cole
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Old 05-25-2011, 05:34 PM
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According to an article in Drag Review (DRM), if want as good of performance in the 1/8 as in the 1/4, divide 1/4 mile gear by .8. In this case 4.11 divided by .8 = 5.13. It should work, unless you have the wrong gears for the 1/4.
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Old 05-26-2011, 09:09 AM
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ok imho and like i said with either gear im running exact same time in both the 1/4 and 1/8 and i have plenty engine in my 55 chevy its a 427 small block motown engine the only thing that changed is rpm ive always ran 5.13 but didnt like turning my engine 8500 rpm and have just recently started run the 1/4 im only gaining about 15 mph from the 1/8 mile mark thru the 1/4 only thing that changed was rpm from 8500 to 6500
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Old 05-26-2011, 03:50 PM
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you are not making any power much after the 6500, thats why at 8500 your running the same time. run the 4.11's at 6500 live a long time, think you need more engine to go quiker not gear
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Old 05-26-2011, 03:50 PM
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Well at least it is consistent!!! I don't think you will see a remarkable difference in just changing gearsets. 8500 seems about right, maybe a little high for a screaming little sbc. At 6500 with the 4.11 gears your probably giving a little bit away. Only you know on here knows all the specs of the motor, how much the car weighs, and what it likes. Run it and have fun, just don't blow it up trying to squeeze the from it.
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Old 05-27-2011, 01:08 PM
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Post up timeslips from 1/8th and 1/4 mile tracks.
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Old 05-27-2011, 11:01 PM
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It's a 1955 chevy 210 all fiberglass front doors and deck lid the engine is a 427 cu small block by bill mitchell racing dunk at 530 up with a turbo 350 trans built by a local builder oh the car weight is 2600 lbs and a 9in ford rear
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Old 05-27-2011, 11:11 PM
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You don't have enough cam and/or induction flow for the 5.13 gears. You ought to try running the 4.11 w/a taller tire to see if the combo actually wants LESS gear.
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Old 05-28-2011, 01:42 AM
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I agree^^^, it will probably respond to even less gear than the 4.11's like 3.90 or 3.73. The Mitchell 427 SBC isn't a really radical race version it's more of a street rod engine, and it is not going to make any power above 6500rpm - it's done and out of breath at that point. Cam, heads/intake manifold and likely your carb are all not big enough to make power above that point. It will rev up there above that, but all it is doing is making noise at that point.

Just an FYI, it is horsepower versus weight that decides Drag strip MPH, and gearing has little to do with it. Pretty much any rear gearing between 3.25 and the 5.13 you have tried will result in the same or similar ET's. If you want to go faster(MPH) you will either have to make more power by either installing parts that will allow the engine to breathe above 6500 rpm and thus make more power, add nitrous or forced induction, or reduce vehicle weight.

Correct rear gearing, tire size, torque converter stall, along with engine tuning may lower your ET by .5 seconds in the 1/4 mile...but none of these things will change MPH much.

The conversion calculator at www.wallaceracing.com also shows the 7.32 1/8 mile time matching a 11.51 1/4 mile time, and shows a 24 mph gain ideally compared to your 18 mph gain.

The more info you can post up about the parts in the car will help folks here help you sort it out. Right now it looks like you are rather down on power if the car really weighs just 2600 lbs - it should be faster at that weight. Right now the HP calculator only shows a bit over 300 hp.
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Old 05-28-2011, 09:19 AM
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the engine dyno was at 530hp not sure which cam will have to find the build sheet but im running a 3500 stall and a 870 cfm holley all you guys help is very appreciated i dont really care about speed i just want my e.t. lower
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