no mph in 408?
#1
no mph in 408?
we've got a 408 stroker thats not mph right. It made 502 rwhp all motor and 684rwhp on nitrous. It was in a six speed car with stock gears and stock suspension and it trapped consistant 120s spinning like crazy. Now we put it in a t/a w/ full aftermarket suspension front to back and a th400 and 12bolt(3:73) and its only trapping 112-115. What could be the issue? the 400 and rearend??? any suggestions would be great!
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Did you check the thrust angle and wheel alignment. I have personally witnessed knocking 7 tenths (3/4 of a sec.) off of a '67 Big block Chevelle by aligning the wheels only! We did nothing else, only the alignment. He also gained almost 10 mph.
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The only reason it was trapping in the 120's was because it was "spinning like crazy" and it had a 6spd behind it.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
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Originally Posted by 1QuickT-A
The only reason it was trapping in the 120's was because it was "spinning like crazy" and it had a 6spd behind it.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
#7
Originally Posted by GOaT Cheese
Huh? I understand the increased parasitic drag from an auto versus an M6, but please explain your tire spin theory. How does hooking slow you down? That hasn't been my experience.
Al
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And...
Originally Posted by 1QuickT-A
The only reason it was trapping in the 120's was because it was "spinning like crazy" and it had a 6spd behind it.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
Now its probably hooking alot better so naturally the trap speed is gonna be a good bit lower than when it was spinning the tires. And on top of that you now have an automatic behind it so its not gonna mph as high anyways.
Datalog the runs, and look at the engine rpm. Then, do a calc to see what converter slip % is.
Also, look at rpm drop between shifts.. Could tell you even more about converter performance/match.
What is the stated stall vs the actual?
A high slip %, and/or a very low drop on the shifts, too much stall, indicates a poor match to the engine performance curve.
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I was looking at that trans and conveter before scott bought it for his car. I saw how much that it got beat on and was a brand i never heard of before and when i looked them up couldnt find anything good about the company so i would say you are blowing threw that thing and need to pick up a yank or ati, you also might want to get a stock stall and put it in and make sure it still is making the power it should. What rpm was he going threw the traps if you figure out your slippage you will know if the one in there now is junk or not.
Last edited by sbcgenII; 10-24-2006 at 08:05 PM.
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If the motor is running good, it's probably the convertor. Get one speced for your use. My 402, T-400, 12 bolt (also 3:73), DR, traps 125.6, with a best of 127, not much difference in MPH on or off the transbrake. This is on motor, with a convertor speced out for nitrous.
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Originally Posted by T6Rocket
Some manual transmission cars can run a higher speed on a pass with severe wheelspin. The wheelspin causes you to hit the rev limit, and you shift to the next gear sooner, all the way down the track. The ET ends up horrible, but the MPH is a "little" higher.
Al
Al
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Might it...
Originally Posted by sbcgenII
I was looking at that trans and conveter before scott bought it for his car. I saw how much that it got beat on and was a brand i never heard of before and when i looked them up couldnt find anything good about the company so i would say you are blowing threw that thing and need to pick up a yank or ati, you also might want to get a stock stall and put it in and make sure it still is making the power it should. What rpm was he going threw the traps if you figure out your slippage you will know if the one in there now is junk or not.
Like I posted, B4.... Get a datalog and see WTF is up w/ the rpms...Simple test/sound results.
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Originally Posted by GOaT Cheese
I've been drag racing for some time now, both auto and manual cars, some hook, some don't, but I've never had faster trap speeds with the cars when they are spinning versus when they are not. As the tires are spinning all you are doing is consuming realestate before the power of the engine can actually accelerate the car. Then instead of running 1320 feet at full power acceleration, now you only have 1150 feet to gain top speed. ( or whatever the distance deduction may be before optimal traction occurs).
Lets say you compare 2 time slips and on 1 slip you went 12.503@114.6 with a 1.65 short time and on another you went 12.58@115.8 with a 1.74 short time then you will see what I'm saying..