MPH vs ET

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72Dart360

72Dart360

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My timeslip shows MPH of 114.23 with ET of 11.372. 60 ft is 1.486. Should the MPH be higher? If so, what fixes it? My car weighs 3350 with driver, 3.91 rear gear, 904 trans with low gear set, 4200 stall.
 
ET with a low MPH is usually a sign of converter slippage. Going to a smaller/better/$$$ converter usually solves the problem.
 
What tire diameter do you have, and what rpm are you crissong the stripe at? Also - what brand and diameter of convertor are you running?
 
I'd rather have your situation than the opposite, high mph and bad et. You have the GOOD side of that predicament.

What's the engine? MPH is HP dependent, ET is chassis/convereter efficiency.
 
Ok, what RPM are you at when you cross the line?? You may also need LESS gear for more MPH. Sometimes you just run out of power before you run out of track.

I had a customer running a 4.30 gear in his last combo, told him to drop it to 3.91 with the "new" engine. They didn't and called me with the same issue. The engine was peaking around 6000rpm, they were crossing at 6800! So they dropped it down, ET dropped and MPH went up. They also dropped the 60ft time as they could control the wheel spin better with the taller gear.

You have the power, now you just need to use it better!
 
Had this problem with my car, was the 906 cylinder heads refusing to move fuel and air, after .500" lift. Car would launch pretty and accelerate down track until about 1000', then go flat. I thought sure I had a fuel problem, so I bought a 450 gph pump and a 1050 Dominator. It liked the bigger carb because, it picked up 1 mph and still it popped at the finish line, on hot humid days.
Confirmed the heads were the problem, with a visit to a flow bench. Raced the car just as it was for a couple seasons. made a perfect 10.90 racer.
 
moper said:
What tire diameter do you have, and what rpm are you crissong the stripe at? Also - what brand and diameter of convertor are you running?
Click to expand...

275 60 15 Mickey Thompson drag radial. Crossing at 6250. The convertor is a 10 inch built by a neighbor.
 
275/60 MT are 28 inch tall...with 3.91 gears....that is not alot of gearing for a small block

need info on camshaft...hydraulic...solid....as the engine might not want to rpm ..

what rpm is your 1- 2 and 2-3 shift?

fuel line...fuel pressure...fuel pump...
 
My guess, a 10", 4200 stall converter is going to be pretty inefficient.
 
Your neighbor built you a very good converter for the 60'. Those times are really fast for the rest of your numbers. A well built converter will surely help. I'd talk to one of the good converter builders, and I'd bet you will probably end up with something a little different then you have currently. If you're ok with it now, then run it and enjoy it as is!
 
70aarcuda said:
275/60 MT are 28 inch tall...with 3.91 gears....that is not alot of gearing for a small block

need info on camshaft...hydraulic...solid....as the engine might not want to rpm ..

what rpm is your 1- 2 and 2-3 shift?

fuel line...fuel pressure...fuel pump...
Click to expand...

Comp Cams solid Part No 20-635-5 252 in, 262 ex @.050, 542 in lift, 555 ex lift 106 centerline / leave line at 3000, shift at 6500 / BG220, -8 line, 7psi
 
72Dart360 said:
330= 4.49, 1/8= 7.11, mph=93.3, 1000= 9.40
Click to expand...


ideal pass with a 11.37 et


60 Foot 1.58
330 Foot 4.57
660 Foot 7.17
660 MPH 94.74
1000 Foot 9.44
1/4 Mile ET 11.37

shift at 6500...did you happen to see what the tach says going thru the traps..
1/4 Mile MPH 116.53
 
Your car should be running high 11 teens with the 1/8 mile it turns. More than likely converter slip is killing it.
The typical 1/8th mile to 1/4 mile factor is 1/8 mile time X 1.57 to 1.58 = 1/4 mile time.
 
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