How high can you and should you spin a 5.3L with a Radix? Right now I am shifting at 6300rpms, is that ok to keep?

 

what pulley size? springs? cam? UD pulley?

 

Where do you make peak HP/TQ?
I spin mine to ~6300, my HP starts to fall off over 6050 and I make peak tq ~4200

 

If you get a dyno done, make sure you pull past the point where you normally shift. Look it over and find the range where power stops gaining and begins to drop. Ideally, you'd find the rpm level where power really falls off and base your shifts on that. You want the most power delivered to the wheels that you can get and you want to stay in that sweet spot as long as possible.

I had 6300 rpm shifts with a 2.75" radix pulley on my SS, which put it way out of its efficiency range. A 5.3 shouldn't have that problem.

 

I have shifted at 7000rpm with a 2.75" pulley when I was running the bigger cam in the 402.I doubt you will hurt the supercharger,shift at an rpm where you are making power,6300 should be about the max with a stock cam.

 

Me too. IATs are through the roof though.

 

I'd start to wonder about springs, too. I shifted at 6300 with my 2.75 pulley regularly but I had a cam and valve springs.

 

Dang you guys are turning some RPM, I keep trying to get Dewmanshu to try shifting at 5,500 like real men do....

 

not sure on his setup cam wise but my stocker quits pulling around 5500rpm

 

i always use my gtech to help me decide when to shift. it is real easy to use. you want to maximize your g's thru the run. the g's before and after the shift should be real close to the same. if there is a big jump in g's after the shift then you are shifting too high. if there is a big drop in g's then you are shifting too soon. easy as that.

here is a chart of a stock truck with stock shift points.



the et's dont mean much here since the launchs were all diferent but you can clearly see the shifts and the drop in g forces. if the shift was held off longer the average g forces would be higher and the et quicker. you can see on the black run where we held it in 2nd at the top and how the g's are a little higher. the 1-2 shift would be the same if it was shifted higher.

it's a sweet tool(toy).