DOTracer
07-25-2006, 09:16 PM
lets' try this again in a different forum.
hello all,
I wanted to see what some of you might feel my combination might do with a tire swap.
3450 lb 79 Malibu stock suspension
461 ci bbc, 13.4 to 1 compression, CFE/BMF 310cc heads, vic jr intake, 1000HP 4150 Holley by Pro Systems, 269/276 @ .050 Bullet roller cam.
th400, 8" ATI flashing 5600-5700 rpm off the footbrake launch
shifts made at 7200-7500 rpm
trap rpm a bit low at 6900 rpm (thinking it should be 7400-7500?)
converter slippage 6.5 to 7%
rear gear is a 4.10 with a 295/54 M/T ET Radial DOT tire
I suspect the 30" tall 295 tire may have been a mistake in terms of killing gear ratio. I recently picked up a slightly used (25 passes) pair of 325/50 M/T Radials which are 28" tall.
My thinking here is to use these shorter tires as an experiment to see how the car would respond to more finish line rpm and more effective start line gear ratio. If the car responds well I could either keep the 28" tall tire, or go back to the 30" tire and swap gears to either 4.33's or 4.56's.
The reason for this test is the 60's have been soft this season after the head/cam swap telling me I need to reconfigure the combination to properly/effectively use the power band of the new engine combination.
Anyway, would like to hear some input on how the car might respond to a swap from 30" tall tire to the 28" tire assuming it still dead hooks as it does now. What should I expect to see?
I have my own predetermined idea, but want to hear others ideas to see if my line of thinking is correct or not.
thanks
Todd
BTW, the current best in good air this past spring was a 9.71 @ 138.5 mph with a 1.40 60. This summer at the same track in 3150 ft D/A air the car ran a 9.83 @ 137 mpg with a 1.42 60'. At a different, yet slower local track the car has run a best of 9.97 @ 125 mph on the brakes (10.0 index class) and that run should have been 9.93 @ 136 with the 60' being a 1.46.
hello all,
I wanted to see what some of you might feel my combination might do with a tire swap.
3450 lb 79 Malibu stock suspension
461 ci bbc, 13.4 to 1 compression, CFE/BMF 310cc heads, vic jr intake, 1000HP 4150 Holley by Pro Systems, 269/276 @ .050 Bullet roller cam.
th400, 8" ATI flashing 5600-5700 rpm off the footbrake launch
shifts made at 7200-7500 rpm
trap rpm a bit low at 6900 rpm (thinking it should be 7400-7500?)
converter slippage 6.5 to 7%
rear gear is a 4.10 with a 295/54 M/T ET Radial DOT tire
I suspect the 30" tall 295 tire may have been a mistake in terms of killing gear ratio. I recently picked up a slightly used (25 passes) pair of 325/50 M/T Radials which are 28" tall.
My thinking here is to use these shorter tires as an experiment to see how the car would respond to more finish line rpm and more effective start line gear ratio. If the car responds well I could either keep the 28" tall tire, or go back to the 30" tire and swap gears to either 4.33's or 4.56's.
The reason for this test is the 60's have been soft this season after the head/cam swap telling me I need to reconfigure the combination to properly/effectively use the power band of the new engine combination.
Anyway, would like to hear some input on how the car might respond to a swap from 30" tall tire to the 28" tire assuming it still dead hooks as it does now. What should I expect to see?
I have my own predetermined idea, but want to hear others ideas to see if my line of thinking is correct or not.
thanks
Todd
BTW, the current best in good air this past spring was a 9.71 @ 138.5 mph with a 1.40 60. This summer at the same track in 3150 ft D/A air the car ran a 9.83 @ 137 mpg with a 1.42 60'. At a different, yet slower local track the car has run a best of 9.97 @ 125 mph on the brakes (10.0 index class) and that run should have been 9.93 @ 136 with the 60' being a 1.46.