How fast with stock stubs and flanges?

[weedburner]

The ratio difference between 1st gear and 2nd gear is going to be a huge factor in keeping the stock stubs/flanges alive thru the shift. It's basically the energy stored in the rotating assy at shift point rpm vs the energy stored in the rotating assy after the shift. The difference between those two energy levels equals the amount of energy released during the shift. Eric JB's use of a 700R4 and a 2500 converter puts more stress on stubs/flanges than just about any other common sbc combination, especially with drag radials and a tire chirping shift kit added to the mix. The tighter splits of the T350 are a far better drag race choice over the 700R4, not only less 1st gear ratio but about 12% less energy release on the 1/2 shift.

 

To help make that statement easier to understand, lets say you have an entire rotating assy (crank/flywheel/pressure plate) out of the engine and spinning on bearings at 1000rpm. That rotating weight spinning at 1000rpm contains a fixed amount of energy that can be put to work. One way to measure that stored energy is to apply a braking force to the rotating assy and then measure how long it takes for that braking force to bring that rotating assy from 1000rpm to a full stop. Lets say a braking force of 100ftlbs can take that rotating assy from 1000rpm to a full stop in 1 second. Basically the energy contained at 1000rpm is 100ftlb/seconds. Sounds pretty reasonable so far, right? 

 

Now consider that the energy stored within that rotating assy is an exponential function of it's rpm. Spin that rotating assy up to 2x the speed, it will contain 4x the energy. Spin that same rotating assy all the way up to 6500rpm, now it contains 4225 ftlb/seconds of energy! 

 

Now further consider what happens when the transmission shifts from 1st to 2nd gear. The ratios in a 700R4 indicate an rpm drop to 3450rpm in 2nd gear after a 6500rpm shift. At 6500 before the shift, the rotating assy contained 4225 ftlb/seconds of energy. After the shift at 3450, the rotating assy only contains 1190 ftlb/seconds.

 

Now the question- where do you think that 3035 ftlb/sec of energy released during the shift goes? 

 

Same thing applies to manual trans gear splits.

 

Grant

 

 

[jnjdragracing]

I just went a 5.23 in the 1/8 th which crosses to a 8.04 in the 1/4. I have been a 8.57@158 . Thanks 

[jnjdragracing]

On 7/28/2015 at 2:25 PM, Eric JB said:

Hey all, Wondering how fast (ET) any of you have gone in the quarter with stock 280 stub axles and flanges? I am not pushing mine very hard with an auto, and a tight converter, and running 12.05 to 12.08. I am putting it up on the converter to stage, so everything is preloaded and there is minimal shock.(235/60 mickey dr's)

 

I would like to upgrade the heads, cam, ect, Should I upgrade the stubs before I go any harder? Thanks.

Yesterday I went a 8.43 @ 166 mph.