What Does It Take . . . - Mopar Tech

Glow Worm · #1 12-12-2007, 06:41 PM

I've often wondered . . . .What does it take to get the front wheels off the ground during take off/launch?

Let's say it's a Duster/Dart/Cuda and the car weighs 2500 to 2900 pounds.

I don't have any plans to do this. I'm just curious.

Correct the car weight if I'm off too much...

Ace · #2 12-12-2007, 07:04 PM

I had 520+ rwhp in a race weight w/me of 3350 in an 85 Mustang GT. 90/10's and 50/50's with an anti-roll bar. It all needed adjusted out for better short times, but I carried the front end with this car with an auto, tight stall, leaving at idle.

Cheapstreet_duster · #3 12-12-2007, 07:19 PM

ofcourse traction is huge factor..
but lets just take a fairly stock vehicle for the approach..
i had a 348 rwhp 418 ftlbs of torque at 4200
in a duster with a transbrake 4200rpm converter and 4.11 gear...
launching off the brake at 3300 it would lift the tires about 2" of air between the front tires..for about a foot of forward motion..
same car with a 410hp engine leaving off the brake ...i get what you see in this picture..plus maybe 3-4" more if its jetted just right..
my car weighs 3410lbs and is all metal no fiberglass anything..
for comparison..Locomotion dartsport runs a 380hp crate motor and he gets a solid 8" to a foot of air under the tires. I dont know how light his car is,,i am fairly sure he has a glass hood and bumpers..
I know of a 410" b motor in a 74 dart that has the front end completely gutted..no rad support ,no inner fenders..and body panels held on with 1/4 aluminum fabricated rods. no interior or dash..but a 12pt cage..
glass bumpers and lexan windows
a t-brake and 30x11.5 tire and a 5.13 gear..get the wheels up 2-3ft no problems.(except comming back down?)
id estimate the hp of the motor at 450hp...but the car is light...especially up front (by design)
so it can be done with modest numbers ...
you can then move/remove weight and or add power...to make a wheelie happen more often...
this is just my experience....but it should be close..
iam sure a torque to front end weight could be factor'd to get a formula..?
cheapst.

Glow Worm · #4 12-12-2007, 07:42 PM

So... Light weight front end (maybe) 350 to 450 horsepower....big torque numbers, excellent grip.....

Sounds simple, but I can tell it is complicted, and $$$$$ is involved.

Bill · #5 12-12-2007, 11:24 PM

depends , mopars make alot of torque anyway , 350-400 horses by what cheap is saying is pretty easy with stock parts , they dont call him cheap for nothing , with the combos that cheap has most of the time with STOCK PARTS.

Mopower71 · #6 07-21-2010, 07:41 AM

So,
Should a Demon ( don't know the weight) with glass hood and bumper, 12pt cage, full interior, all steel big block,727 no brake, 4500 tight converter, 4.11 spool be able to lift the tires?
Ran an 11.83 consistently 3 times with no tuning, the time I took it to the track. On 325x50x15 BFG street tires.

77 Dragracer · #7 07-21-2010, 12:54 PM

My Aspen is 3420# with driver all steel and the wheels started to lift when i went to a TCS 8" converter that has a 5400 flash to it but they call it a 4000 stall?? No trans brake in this car either but has 4.30 gears with 9X30 Hoosier radial slicks.
As for Myrons car his Dart Sport is all steel to meet Stock specs and weighs in at 3500 + with him in it.Stockers run alot of stall usually in those cars and high rpms.

Brewzer67 · #8 07-21-2010, 04:56 PM

I have video somewhere of my 4200 lb. Coronet lifting the driver side tire 6-8" off the ground when I was running 12.0's on...are you ready for this...20 year old 7" JC Penney brand cheater slicks on steel rims that I borrowed from a friend. They were pretty hard and I had to smoke the hell out of them to get them to grip, but when they did, they hooked hard. The first time I did it I thought I broke something because the car made a horrible noise from the differential. It almost sounded like a rubberized version of those cheesy wire curb feelers. I didn't know I had lifted the tire 'til I came down pit road and was greeted by my buddy that was video taping. He was jumping up and down and just kept going "holy sh@t, Holy sh@t, that was awesome, holy sh@t".

That was with a 448" stroker, mild cam , 4.30 gears and a 3500 stall leaving from idle and hammering it. 60' times were typically high 1.6's, low 1.7's.

I loved that motor! Still have it...

Mopower71 · #9 07-22-2010, 12:17 PM

So do you think a set of 4:88's behind the Big Block with 27.8" tires will run out of rpm's before the traps?

How do you guys loosen up the front suspension? Mines fairly stiff. I am thinking of trying my summit cheapy adjustables, as it has some stiff adjustable Koni's

Mopower71 · #10 07-22-2010, 12:30 PM

Should I leave the bump stops off for the upper control arms or should I put them on, or run a lower set?

Launch from idle or bring the rpms up to what point?

77 Dragracer · #11 07-22-2010, 01:47 PM

The only thing with launching from idle is you'll have horrible reaction times.But if it's the high flash & harder hit your looking for that will do it

Brewzer67 · #12 07-22-2010, 04:22 PM

Quote:

Originally Posted by Mopower71

So do you think a set of 4:88's behind the Big Block with 27.8" tires will run out of rpm's before the traps?

How do you guys loosen up the front suspension? Mines fairly stiff. I am thinking of trying my summit cheapy adjustables, as it has some stiff adjustable Koni's

If you run that gear combo, you will be pushing 6500 rpm through the traps at 110 mph. With that gear you run out of motor in a hurry unless you want to spin the crap out of it. That is the reason I have always run a stroker motor. I can run a smaller gear and use the torque from the stroke instead of spinning it to get the same times. High RPM=Broken parts + shorter life overall.

I have 318 torsion bars, polygraphite bushings and Lakewood 90/10's up front and get pretty good rise/transfer. I keep everything lubed up with Mobil1 synthetic grease. I also am at an approx. 46% front - 54% rear weight bias so that helps a lot.

Mopower71 · #13 07-22-2010, 08:58 PM

I pulled one of the Koni's out, and it seems a bunch looser than the Doetsch Tech 3 way adjustable (Summit 3 ways).
I'm going to pull the other shock tomorrow, se the car on the ground and see how loose it is.
The way it was/is you can push the front fender down and it is very stiff, no bounce, and barely any movement. Same with pulling up on it.
I grabbed my micrometer and measured the torsion bars. .840" is what it reads.
Anyone know if these could be the drag bars, /6 bars or? The car did have a small block in it.

Mopower71 · #14 07-22-2010, 09:05 PM

Could it be all the new parts are holding the front end to tight.
Is there a way to loosen the bushings up?

Mopower71 · #15 07-23-2010, 09:30 AM

I checked the number on the end of one torsion bar. 888R which is a /6 bar.
That's a good thing.
Now I'll go pull the other shock and put it down and see how tight it is.

Mark · #16 07-23-2010, 07:15 PM

Quote:

Originally Posted by Brewzer67

If you run that gear combo, you will be pushing 6500 rpm through the traps at 110 mph. With that gear you run out of motor in a hurry unless you want to spin the crap out of it. That is the reason I have always run a stroker motor. I can run a smaller gear and use the torque from the stroke instead of spinning it to get the same times. High RPM=Broken parts + shorter life overall.

I have 318 torsion bars, polygraphite bushings and Lakewood 90/10's up front and get pretty good rise/transfer. I keep everything lubed up with Mobil1 synthetic grease. I also am at an approx. 46% front - 54% rear weight bias so that helps a lot.

You could be like me and have 70-30 weight bias.

Mopower71 · #17 07-23-2010, 07:32 PM

Quote:

Originally Posted by Mark

You could be like me and have 70-30 weight bias.

No thank you.
I just want to loosen the front up.
I wonder how close I am to your 70/30 with the all steel 440 up front?

Mopower71 · #18 07-24-2010, 08:51 AM

I removed the shocks, loosened both ends of the strut rod on the passenger side, push the passenger fender down car drops comes back up and stays. It does not bounce up and down like it has no shocks on it. It's not as stiff to push it down, or pull it up.
Next I jacked the car up, loosened up and removed the torsion bar adjuster. Found the lower control arm nut loose, just snug, not much more.
Tried to pick the rotor up to move the suspension. feels like it weighs 50+ pounds just to move it upward.
The upper control arm rubber bushings don't appear to be binding as you can see them rotating, and not twisting.

Am I wrong in assuming with the strut bars loose and the shocks out, it should bounce up and down a few times?

Is it time to pull the torsion bars out and remove the lower control arm?

Anybody have the torque specs for the suspension nuts and bolts?

Mopower71 · #19 07-26-2010, 08:59 AM

After loosening up the strut rods , and lower pivot, and taking the torsion bar adjusters out, lubing up the lower and upper control arms. I tightened/ torqued everything back up at ride height. Put the shocks back in, and now it is a bit looser.
When I push it down, it moves a bit farther and easier than before. It also does this after pulling it up. And either compression or extension, it returns to where it started from.
Glad I climbed under and found the loose lower control arm nuts.
Today sometime I will get it out and go for a ride.

Brewzer67 · #20 07-26-2010, 04:17 PM

Quote:

Originally Posted by Mark

You could be like me and have 70-30 weight bias.

Have you thought of throwing a few dead Chebbie motors back there to improve your ratio? I'm sure you can find enough laying around

Mopower71 · #21 07-26-2010, 07:18 PM

I need to find some blocks of lead, to offset my big block.
Where can I get some, and what's NHRA's requirements on weight boxes?

Mopower71 · #22 07-27-2010, 07:37 AM

View of the Demon at the track. This was 4 years ago.
http://www.youtube.com/watch?v=CUd8pXtVc1U

Mark · #23 07-27-2010, 07:51 AM

Quote:

Originally Posted by Brewzer67

Have you thought of throwing a few dead Chebbie motors back there to improve your ratio? I'm sure you can find enough laying around

I could always throw a few illegals back there God knows we have enough of them.

Phil · #24 07-27-2010, 08:03 AM

Not for long though....

Mopower71 · #25 07-29-2010, 10:41 AM

Went for a ride, and it handles much better. It's now softer up front, and I set the rear shocks on 4. They are Rancho 9 way adjustable that I had set on 6.
I'm pretty sure the front end work that I did will help on launch, if I ever get it back to the track.