Questions about drag car launch.

Tech questions that don't fit above forums

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T RICK
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Post by T RICK » Mon Dec 26, 2005 3:33 pm

Brian in my way of thinking if you raise the front end you are limiting the travel from nuetral to max extension. This will slow the speed when it hits full extension. I would put limiters in and leave the front down. Others may have some suggestions as well. Picture the ladder bar as an arrow pointing to an imaginary spot ahead of the car. If you raise the bar the line going through the center of the engine. The weight below the line will not transfer back to the rear wheel during lift and will also act as nose weight. Result is poor lift and poor load on rear wheels. If you lower the bar then you will see it points below the motor and all the weight again above the line will load to the rear and with no weight below the line to hold it down. In basic princple low bar means more lift. High bar means less lift. I will leave the shock and springs to some one else as with the slicks things have changed a bunch but yes if there is little or no seperation at the rear tire to the fender something is probably up with springs and schocks

prochamp
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Post by prochamp » Mon Dec 26, 2005 9:35 pm

hi brian,what width rim are you using with that tire?it shouldn't be under 10".if it is look at your tire wear & you'll see you're not using it from side to side.i've had quite a few of my buddys do the same thing & went narrower in tire to match the rim and it helped traction alot due to more tire control.i run smallblock a-bodies also.you might try adding more travel to the frt with shorter a-arm stops.i would lower the bars down also & i would run staggered shock settings in the rear.you should get rise in the rear just like ss springs(same principle)run the lft shock stiff & let the rt side seperate faster & stay up.you ought to have about 5degrees of pinion angle.when you stage try 2500 and let the converter use all the flash it can,that will let the motor rev to it's powerband + will let your suspension use all the travel it has instead of putting it in a bind trying to "hold" it.as far as tire press. with the right tire/wheel combo i would think 10-13 on bias & 15-18 on radial slicks.oh yea,have you tried any weight adding in the rear,get your bias right and see how consistent it gets. good luck Rob.

ou812
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Post by ou812 » Mon Dec 26, 2005 10:09 pm

Well, 1.43 60ft isn't bad for probably 530HP. And I do know some about suspension...not a total dummy.
Tire is M/T 28x10.5 on a 10" rim. Actually the car seems more consistent launching at a lower rpm, so I might try that as well.
Even though I already said this, here goes again: Front end is 1 to 1 1/2 inches lower than stock, 6cyl torsion bars, Koni shocks set loose. If I cut the A-arm snubber down, there wont be much left to keep metal to metal contact...thought that was a bad thing. My basic question is why when I went from 2 degrees down (lower bar) to level with the ladder bar position, did it not want to hook? It seemed to help when I went to looser shock setting and lower tire pressure...maybe it was just the track. I can say that I was trying to launch it as hard as possible, so I was up on the converter hard...maybe not a good thing. Seems to want to launch at a higher rpm so this is why I think a looser converter would help.

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Post by Speedy Goomba » Tue Dec 27, 2005 11:38 pm

To make your tuning go smoothly, lets stick with one major change at a time.

Shock settings can be changed at the track. Infact theirs two brands of Bolt on shocks that i recommend.
Koni SPA1 or if you dont mind Spending the money Afco Double adjustable.

The first major changes i would make to the car are to increase suspension travel.
You should also work to minimize "Sticktion" in the front suspension. Not nessecarily a loose front suspension, but one that works through the travel freely.

When making shock setting changes go by my guidelines for making a change.
If the car Initally hooks then spins, tighten the rear shocks in extension. Generally when this happens its due to the rear shocks allowing the front end to drop too quickly. it will be plain to see in a video, the rear will fully extend or extend alot and front will come up then quickly drop.


If the rear of the car doesnt "Anti-squat" then loosen the shocks until best 60ft and highest Wheelie is found. No Anti-squat due to stiff extension will cause the sidewalls of the tires to be yanked up and the tires will spin.

I Keep the front shocks set full loose on extension, unless the car is wheelying too high (over 2' of air under the front tires) then tighten them in extension.
11.15
117.42MPH
1.46 60 foot(footbrake)
7.03 @ 94.65
3215 lb. '67 Camaro

http://i27.photobucket.com/albums/c181/SpeedyGoomba/

T RICK
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Post by T RICK » Fri Dec 30, 2005 8:25 pm

Speedy, what effect do you see or have you tried putting weight under the back seat so it is low just in front of the rear axle? We did this in snow country and it helped on two wheel drive cars.

Speedy Goomba
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Post by Speedy Goomba » Sat Dec 31, 2005 12:45 am

I havent personally tried it. I'm currently moving some weight for next season, but to the trunk.

Supposedly thats the best spot ET wise to have the weight, directly over the IC is going to cost less ET then in the trunk. How much i cant say without my own testing.
11.15
117.42MPH
1.46 60 foot(footbrake)
7.03 @ 94.65
3215 lb. '67 Camaro

http://i27.photobucket.com/albums/c181/SpeedyGoomba/

T RICK
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Post by T RICK » Sat Dec 31, 2005 10:13 am

What are you allowed to use for weight does it have to appear as stock componets our can you build shot tubes? I made steel shot tubes out of scraps that works good. I will tell you if interested. I was thinking you could even bolt them to the rear seat belt anchors with out welding on the car.

Speedy Goomba
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Post by Speedy Goomba » Sat Dec 31, 2005 11:42 am

Weight in that form is legal. The rules require it to be mounted to a frame structure (Frame or crossmember). So that would be legal it spanned that area and tabs that were welded to the frame were made for the mounting. Using two 1/2" bolts.

Right now i have a weight box that i will be mounting with a frame to hold weight.
11.15
117.42MPH
1.46 60 foot(footbrake)
7.03 @ 94.65
3215 lb. '67 Camaro

http://i27.photobucket.com/albums/c181/SpeedyGoomba/

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