I have a 87 IROC w\ 305 4bbl, 700r4 tranny and 4:10 posi rearend. I want to know if anyone has any tips (besides the obvious running the same water temp and shifting at the same RPM's) on making my car more accurate. I cant use a transbrake, air shifter or any electronics. The 305 is a 450hp engine and the tranny is a built up 700r4 w\ 2400 stall converter and B&M hammershifter. I want to beable to dial in at, lets say 12.50 and run a 12.50 or a 12.499 or a 12.501... just to give you an idea what im looking for

 

Become god

When you find out how, let me know.

As the weather changes over the day, a car can become inconsistant no matter what you do but there are many things to make it better.

Eliminate all the slop from the suspension. Factory suspension parts are not designed for performance. They're to give a soft ride. Change all the rear suspension parts to aftermarket and replace all the attachment ends with poly bushings or heim joints. The factory rubber bushings are unpredictable.

SFC, 6 point roll bar (even in a slower vehicle) will all help stiffen the chassis. A chassis that twists is unpredictable since energy is going somewhere else and you can't control it.

Slicks to eliminate wheel spin but after all the suspension has been upgraded.

Common stuff such as making sure the vehicle weight is the same each time. Making a pass down the track burns fuel. Each time you make a pass, the car gets lighter.

Make sure the tire pressures are the same each time. Even 1/2 pound can make a difference.

Convert the fuel system to alcohol. Alcohol engines are more consistant because they're not affected by the weather as much as a gasoline engine.

If I can make 3 test and tune passes withing .010 seconds apart I'd be happy. Most of the time it's more like .050. It's not easy to be able to run an identical number each time. That's why bracket racing isn't as easy as it looks.

 

Gene, it's impossible to make a car run the same every time out. My car runs 13.30's to 12.80's depending on the time of the year. Air tempeture, humidity, barometer, air density, track conditions, and wind are variables that change between runs. That's why its important to do everything the same each run. Anything different adds to the list of variables. Keep a detailed log of each run. The dial in is one of the hardest things in bracket racing. I make my time traial runs and use them as a baseline. I then adjust for changes in the wind, air density, cloud cover, tempeture, rising or falling barameter, and track conditions. Say I run 12.50 in time trials. When elimination start I see that the air density droped by 1000 feet. I know that my car will run faster because of the better air. I may dial a 12.45 or keep the 12.50 and know I have to tap the brakes before the finish line to keep from breaking out. You have to keep detailed records of each run. Then you can make some logical decisons on your dial.

 

Same gas and same amount of it.
Same air in tires
Same launch rpm
Same shift points
Same lane
Same rollout
Same burnout
Same oil and water temp
Same tranny temp


It doesn't matter. The car will still have a mind of its own.

You need a weather station too. All runs that are good runs need to be factored in. If you spin the tires, miss a shift of something, don't bother with the data. If you do it right, write it down.

Compare and correlate the data and add a dose of common sense and maybe you will be right more often than not.

Also, factor in whether you are chasing or being chased, and whether by a lot or a little. More races are won/lost on mistakes than anything else...