Starting the fabbing process of putting a Dana under my junk. My question is how much et would I lose dropping from 4.30s to 4.10s? My combo is a 10.6 to 1 440, in a 3800 lb car, 28 inch tall ET street radials, 8 inch TA converter that flashes 4900ish. Best ET is 11.33@ 117.72, turns 6500 out the back. Best ets are shifting at 6200.


Ive got 4.30s in the 8 3/4 in it now and Ive got a 4.10 R&P for the 60 already, Id like to not have to buy 4.30s unless there is gonna be a big difference.

What ya think?

You may not see much difference. While I did make some other slight changes to mine I went from a 4:88 to a 4:56 and so far it has stayed pretty close ET wise. I did have to play around with the shift point a bit to find the new sweet spot but I'm not sure if that was due to the new gear or the slightly bigger cam. (I went from a 525 hyd to a 555 sld with roughly the same dur.)

My is if you already have them, use them and if you find it doesn't like it it's not that tough to swap them out later.

went from 8 3/4 with 4.30 gear to dane 60 with 4.10 gear and picked up a tenth

We run a similar combo. 3600 pound N/SS car. .060 426 wedge, 12.2:1. We have a converter that stalls at 4200rpm. Our car picked up two tenths by swithching from 4.30's to 4.56's. It's kinda working backwards, but I think for the weight of the car you're running, 4.56's are perfect. We run a 29.5" tall tire.

There is a formula that works very well concerning tire size, et, and MPH with a specific gear. I have used it on a number of our cars. It always is very close.

[(MPH x 17.6) / (tire o.d. x 3.1415)] x 60 x gear ratio = RPM's at the traps.

Use an ET slip that was from one of your previous bests. Make sure the input info is good. It should tell you what you need. Tom

I dont think you will see much change if any. I run 4.30's also but I only ran them because I had them. I do like them as I like a nice launch but I was going to run 4.10's or 3.91's with a 28" tire so I just use a 29" tire with the 4.30's. I would do it as you can always go to a slightly smaller tire if you need to. Ron

I tried going to a 4.10 from a 4.30 and ran the same ET but was more consistent with the 4.30's.

Im thinking you will not gain any ET but loose it, What are your plans for the car, is it street strip or just all out race car? I myself would run a higher gear, 3.91 or 3.73 gear with a 28" tire but thats just me, you have a BB with gobs of low end. Should pull like crazy out of the hole with little RPM....My Phill