traction pointers anyone????

[sup_duster]

hello. just have a question for any of you guys out there. got a 71 340 duster that im going to be taking to the track for the second time (first time ran a 14 with no traction) and i was looking for a few pointers. the first time i had no posi--it was already done! no pinion snubber either. since then i've rebuilt and installed a suregrip with 4:11 gear, adjustable snubber and line lock to toast up the tires a little. i was just wondering about any rules of thumb for rear tire pressure, snubber position and how to generaly position rear air shocks for maximum weight trasfer and traction.
any help is a big help! thanks!

[440dart_72]

what kind of tires are you using?

[sup_duster]

M/T 60 Indy Profile
H=27 W=10.5

[1972roadrunner]

personally, i'd go to a 50 series tire...but thats just me... another thing, if you have no traction wil airshocks, best bet is to dump them... or drop your psi...how much do you generally run? i constantly have about 150psi in mine (i know, stiff...but my tires are too wide...) but my car hooks up great! i would say, maybe around 90-115psi...unless your tires rub...experiment with em...see what your car likes best.

good luck!

[rumblefish360]

When you mentioned shock position, it sounds like you have air shocks. If you do, run as little air pressure you can. So long as it does not rub the tire to the fender. Other than that, drag shocks will work best. 90-10 up front, 70-30 in the rear should do it. Though, thats not in stone. Best to get 3 way adjustables from summit, comp etc...
Run the pinion snubber about 1/2 inch or less to the floor pan.
Heat up the tires a little. See how it grabs. A reduction in air pressure will yeild better results than heating up the tires more on the second try. Actual pressure is hard for me to recomend.

[1972roadrunner]

Originally posted by rumblefish360
When you mentioned shock position, it sounds like you have air shocks.

i do...remember? i've got shackles too!!



i know i know...y'all don't like the shackles...but it helps my shocks out a little...

[dirty dan]

Rumble fish 360 is right on target.
follow his recomendations and your duster should
jump and run.
You`r tire size and gear should work real well with your 340.
I would say it would run 13`s in the 1/4 and 7`s in the 1/8.
Depending on your engine settup.

[sup_duster]

thanks for all of the sugestions guys! im probably running about 25-30 psi in my rear shocks right now and ive actually got the snubber resting against the floor pan a little. i tried leaving it about 1/2" away from the floor pan, but, i think it works better if its touching the floor pan a little bit. as long as i dont pack my car with people.....do you think theres any other reason why i wouldnt want to rest the snubber a little against the floor? im running 23 psi in my rear tires now and also, is it not a good idea to run air shocks without any air asl ong as you make tire clearance?.
any help is a big help! thanks!

[dirty dan]

You should have some air in the shocks .but only a small amout .
The shocks do have a job to do. If you leave them empty 2 things happen 1 is they can not function,2 you risk damageing them.
how many psi will very from car to car.
I would add just enough to start lifting the car.
Check the pressure and us that # to adjust from up or down
wich ever it likes.
remember this may efect your snuber adjustment.

[MJD]

Set your pinion snubber down from the flor pan. You want the car to squat at the back when you launch (wieght transfer) and if the pinion snubber hits too soon your back stays up and you lose wieght transfer and traction. Ideally, your pinion snubber should be set so that your car squats fully on launch and the snubber hits the floor pan at that point.
As for the air shocks, have a friend watch from behind when you launch. Set the air shock on the low side to a higher pressure so the car leaves flat. Both shocks should have as little pressure as possible to start with though. Experiment a little and be sure to have someone watching the car's position when you take off otherwise you are guessing at your changes.
I set tire pressure by doing small burns on an empty street, find the pressure which leaves a full width contact patch.

My 2 cents.

[Dart]

MJD is right on. You want around 1" between the floor pan and the snubber. That is THE most critcal part of setting up the rear suspension. I would consider ditching your shackles. The shackles throw off the geometry. If you have weak springs, get them re-arched and have a leaf added.

If you add the leaf they aren't quite as stout as the pro stock springs MP offers which is good for the street.

[rumblefish360]

No squat! Rise. MoPars rise in the rear. If your cars squating, somthings wrong.
GM's squat.

[Leigh]

With stock springs, the snubber probably will like being close to the floor pan. If not, you will get huge pinion angle change. You could remove the rear segment clamps, maybe leave one on nearest the rearend. Leave the spare tire in. Can you run more air in the passenger air shock? That will help preload the suspension. Measure the ride height as rest, with you in, and add .125 to the left front t/bar height. It will screw up your alignment, but, raising the front quite abit causes the crank centerline to raise, which helps the car start to pitch rotate earlier. Something to think about in the future. Disconnect the front sway bar. Anything else I can think of cost's $$$!!! Have fun

[sixpackcuda]

I agree with Dart, dump the shackles and air shocks and get a set of super stock or heavy duty springs. Do you need the shackles for tire clearance? Can you use a different offset wheel?

[dans76sport]

under no condition do you want the back to squat first. It must lift to get the weight of the car to push the rear tires into the ground. another thing to consider is with your rear shackles as long as they are, your shocks are probably too short. On launch with the snubber being pushed into the floorboard the back of the car will rise. If you shocks run out of travel it will pull the tires up slightly and you loose traction. I've been told 3 inches longer than you need at rest is good. Just my 2c's.

[coolcarz]

I'm not so sure about the thing that mopars rise in the rear, mopars have snubers just for that reason , cause they squat , chit and git, all my mopars 71 duster and my 64 belevdere squat i run 10'' tires under the wheel wells , the 64 can take 11'' if i wana in wheel wells setting low too!! I've never been impressed with shackles and air shocks, especially on a Mopar, stink bugs and mopar dont go together... for me anyway ,, stock height or lower is the way to go, most mopars have no problem stuffing big ol tires under wheel wells, a 9'' or 10'' street slick or comparable it will hook, never really seen to many mopars with traction bars<-- dont need em........other family members have the mopar, 65 dodge truck 440 auto runs 12:60 it hooks, 70 roadrunner 383 4 spd runs 13:50 it hooks with street tires + pinion snuber 1/2 to 3/4 in from pan list goes on.......maybe if you are power braking it lifts release the brakes it squats, or my cars do, im sure there is nothing wrong, thats mopar.... chevys lift i always thought with the spring set-up, wheel hop, need ladder bars , traction bars or they need a 1200lb hog in trunk... mother mopar love us in some ways hates us in other ways,,,, but when it comes to hook'n she loved us,,, how you drag race makes a diff too,, example, just got duster running , went to grudge nite at strip on street tires 9'' big O's hehe.. dialing in carb made 8 passes, wife made 1 (her last one too!!) I was running 14's every pass did the big burnie every time shift at 6000, let wife go ,, no burnie no 6000 shifts set tach light at 5000, cause she never drag race before (i was scared for me motor) well she ran a 13.91. stopped tuning carb 5 run. hummmmmm

coolcarz

[1972roadrunner]

coolcarz: where do you find a 10 foot wide tire?? (10')

hehe, hopefully you mean inches...(10")

[coolcarz]

No I meant ten foot lol.... amayzing what one little " ' thing could mean something so much bigger...... hehehe lmao!!!!! ya wana hook get these 10 foot wide tires that will shrink to fit under your 11.5" wheel wells , they are the greatest!!!!!! buy a set now and get a free shoe horn to help with the installation............ note to self( proof read all replies before submiting) .... good catch 72 roadrunner..... hehe

coolcarz

[PRO]

Youll be lucky to get much traction with street tires,straddle the existing tire marks for best traction otherwise youll be in the rubber laid down by everybodies slicks and itll ball up under your hard street tires.A snubber and air shocks are an oxymoron,as are shackles,ditch em 1st chance you get,run XHD mopar springs(not SS) and regular shocks(no shackles) then set your snubber to 1/2" clearance,then itll try to hook but not really until you get some slicks.Mopars that rise in the rear have mega hp and are trying to actually wheelie,cars w/o that much hp will squat in the rear thats why SS springs belong in cars that have a serious hp to weight ratio.You can run as low as 12psi in your street tires but sneak up on it 2-3 psi at a time,itll feel sloppy in the rear especially when you let off at the finish.Youll want to try to be on that ragged edge of traction versus wheelspin so youll have to feather the throttle,most likely you wont be full throttle in 1st until the top of 1st gear........PRO......

[gotcha]

The question is certainly a legitimate one, which applies to most first attempts on the track. There is about one second in just the suspension alone. The A-body is lucky in the fact that it has the correct 20.5 inch front segment on the leaf. Without going to Super Stock Springs, you can add a half or short leaf on the right rear. Remove or disconnect sway bar. Pinion snubber about 3/4 from the floor. Possibly reinforce the floorpan at point of contact.
As the car launches, it should rise in the rear. Watch the separation of wheel opening and tire. When the leaf spring suspension on a Mopar is working there should be rise, not squat. The shackles are not the best idea, but the front of the spring should do the work. As the tires bite, the front of pinion will attempt to torque up and contact the floorpan. The short front segment will stiffen and lift the body, which drives the tires into the track. Tires should be 26 or 28 M/T ET streets or slicks for best 60 ft. times. The right front torsion bar or ride height should be about 1/2 to 1 inch higher than the left. Put the widest slick you can fit. Most people use the air shocks for tire clearance. As someone said earlier, you can preload the right rear, but shocks alone with the proper setting can result in 1 tenth in 60 ft. time. HAL makes an excellent street and strip shock. Speaking of shocks, use the longer shocks from a C body or Dodge pickup 72-81. You don't want to run out of rise (sorta like a dog on a short chain) I use about 12 lbs. of air in the slicks depending on the track. Converters are worth a ton in 60 ft. and ET. A good working leaf spring mild motor car can 60 ft. 1.60's and the superior cars will avg. 1.48 range. Work with your suspension and you will be pleased with the results. Sub frame connectors are a must for great results. Good luck and glad to be a member. Bob Doty gotcha@acnet.net.

[rumblefish360]

For a first time reply...Wellll done!
I've told you all before, I'll say it again, you want to rise. That's the way it should work. That's the way it was desighed.
Thanks to all my supporters on this.

[Leigh]

It all sounds good, Bob, except the passenger side ride on the t/bar. That preloads the LEFT rear slick, not the right, which is the wheelspin prone side.

[gotcha]

Leigh....I have worked with cross weight for many years, and you are exactly correct about the left rear slick. We do this only marginally to equalize bite on some Sure Grip rearends. It does work as the leaf cars have a tendancy to over rotate or body roll on the right rear slick. I use this to balance the rear when not using a full spool. Just giving the info we have used for 30 plus years of mopar chassis tuning and drag racing. This also helps if the car is not launching straight. Usually with older A-bodies, the bushings are not replaced, or made solid and the housing is a little of alignment. Right rears usually take the most abuse.

[Firelord]

At the risk of sounding ignorant, I'll ask- what is a pinion snubber? Anybody have a picture of one?

[gotcha]

Firelord....for lack of a picture, the pinion snubber is a relatively small pyramid shaped piece of hard rubber mounted to the nose of the pinion above the yoke, that absorbs the upward movement of the pinion as it tries to strike the floorpan of the car above it. This produces a snubbing action that takes the violence out of hard launches. Kind of a mini shock absorber that works like a rubber donut.

[Firelord]

Thanks! Just to clarify- since here in PR a lot of the terms in Spanish- The pinion is at the end of the tranny and the yoke is right behind right?

[slepr1]

Originally posted by Firelord
Thanks! Just to clarify- since here in PR a lot of the terms in Spanish- The pinion is at the end of the tranny and the yoke is right behind right?

Pinion is in the rear end housing, part of the gear set up. Yoke attaches to it.

Hey Firelord, I love P.Rico. Especially those women...Mmmmm.

[Firelord]

Thanks.

I love them too. 4 Miss universes in 30 years in an island of 4 million people. Says quite a bit!