I had a question about running my car in the 1/4. I have taken it many times and seen falling times as my mods list grows. I basically roll off the line at 2500 and feather the clutch, shifting at 6100 for 1-2, 2-3 and 3-4. The problem is I almost have to shift into 5th, once I do, my times drop.

My best time with street tires is only 13.6 @103.7. I am working on the cars issues under a separate thread and think I have that part of the equation licked for this season. I wanted to focus on the issues with the driver in this thread.

Any advice?

 

posting 60' as well as 1/8th mile times would help.

 

Sure-

2.051 60'
8.801 1/8 ET
80.78 1/8 MPH

13.615 1/4 ET
103.73 1/4 MPH

 

You shouldnt have to shift into 5th gear with 4.10s. 6000rpm in 4th gear with 4.10s equates to 112mph IIRC with stock height tires.

 

I did change my rims to the afs zr1 replicas running 275/40/17s.

 

I am also using the factory tach.

 

The 275/40/17 still has the same diameter as stock 245/50/16's, so you're shifting way before 6100 rpm, although your factory tach may say it.

www.f-body.org/gears

You should be able to run out 4th with no problem. You may even be able to shift higher according to the stock Tach than 6100. Try shifting at 6500 and see what she does. I'm running a cam that is similar to the hotcam, but with less exhaust duration and less lift (1.5 rockers), and I shift at 6000 on my stock tach (which is correct apparently) and I just shift into 4th as i'm going across the traps at the end of the 1/4 with the stock 3.42s. According to that site, the top of my third is 103, and I'm trapping about 103, so my tach is correct. Yours is probably wrong if you are hitting 5th and shifting @ 6100 if you're only trapping 103.

 

I run the same setup trapping a best of 115mph in 4th @6100-6200. You shouldnt have to hit 5th.

Shifting the hotcam with stock heads at 6500 isnt a good idea, power drops off after 6200, at least with mine it does and its running very well.

 

How could my factory tach be that far off?