Launch critique

https://youtu.be/1H3bCkPQVMM. Hope the link works but this was taken on a cell phone. After going to a Bob's profab kit with afco double adjustable shocks shocks and 250 lb coils my car will not transfer or rotate the weight to back like I want. Rear shocks are QA-1 single adjustable with 150 lb springs with ladder bars, bars are leval with the car. I've adjusted the front to full loose and rears from stiff to full soft. It use to 60 foot in the 1.39 to 1.41 average now with changes I did get a 1.35 out of it but I feel it chattering the rear tires. I've tried calling Bondo Bob but will not return my calls for help. any thoughts on getting the car to transfer a little better?

What exactly are you trying to get it to do that it's not

Being a A-body those rear springs are too stiff
so the design length on the shock will be way to
long.. measure the design length.. its not separating
the body(lifting which is planting the tires).. you want
just enough spring to hold the body up.. about 110-120
depending on the rear weight

.

Monte, this launch is footbraking it and with the TB it spins. My car use to stick the front up about a foot off the ground and dead hook, with the new coil over front end it seems the car is bound. This front end is much more stable but I put another 100 horse or so and a brake. I just can't understand why it doesn't pull the front a little higher and help plant the rear?

Of course it's separating, you can see it in the video when he brings the motor up. Probably raises the body an inch. I agree the spring is too stiff, but that don't keep it from separating, unless the shock is completely stretched out, which it doesn't appear to be

If it needs to hit the tire harder, raise the front of the ladder bars and maybe some more air. What tire and what pressure. The front way loose is not going to be what it needs.

I agree that your rear springs are too stiff. All ladder bar cars separate, that's just what they do, but a softer spring will give you some stored energy and let it separate easier if that's what it needs. You probably need a better rear shock as well.

Without seeing a video of a brake launch, it's impossible to say...........but I would about guarantee it is NOT blowing the tire off at the hit. It could actually be hitting the tire TOO hard and topping the front out, which will make it spin instantly.

You say you have 100 more hp and a brake. That will definitely hit the tire harder than it did. I know you changed the front and now it won't work, so that is where you are looking, but doubt that is where the issue lies.

Contrary to popular belief, the more power you make, the LESS aggressive you need the chassis. More power works current chassis settings harder.........so, if it was dead hooking before, it may be punishing the tire now

I am down to a 220 spring on the front of mine. 3.5 of front seperation.

I was told a notable mopar guy runs a 14" 180 spring on a 12" shock

IMO, on the hit your not getting Near enough Rear separation. Your front suspension is to loose and popping to high up then rebounding back down causing you to spin.

So, IMO you don't need a looser front setting. From the vid it pops up right now and bounces several times while unloading the back. I think you need to promote rear separation. The front needs to come up more gradually and smoothly. Next time out can you get a vid from the other side too.

just enough spring to hold the body up.. about 110-120
depending on the rear weight

[/quote]

Mr P, the rear springs are 12" and 130 lb, not 150. I'll take pix of the shock settings & post also.

Def way to much rear spring...One thing to consider is the converter in the equation. IMO the video quality aint helping me at all, but hey I'm old. One big issue with those front coil coversions is way to short a shock, not enough travel IF you need it.

Here is where I have the fronts

Rears

I agree, it does separate when he brings the motor up. Cant see it raise after that on launch, looks likes it remains level or almost squat. Not a really clear vid though.

What is your front end weight?
Mike

I don't have access to scales right now so I can't give you a good answer. Before I changed to the coil over kit it weighed 3150 with me in it. Here's a pic of how it use to leave before Footbraking.

If the car is sitting where you want it........judging by pics and spring platforms, the rates are fine.

As far as how it leaves, do you WANT it to carry the front high, or you just think it should.

My main concern is is chatters the tires on every launch only footbraking. My feeling is it not rotating up enough to stick the back.i can't use the brake til I get it to stick footbraking. Although the front coming up like it use to would be a plus, I just can't understand why with more power, a brake, and the converter adjusted to the new power it will not stick. I've only got 10 runs on this combo so I'm adjusting most every run.

Small block car?

No, low deck big block.

Get some softer front springs. I'd try 200#/" or less. Just push down on the front of the car and see how stiff it is and compare with other cars.

I know someone with an E-body with a big Barton hemi who spent big bucks on a new front suspension and got the same results. All you gotta do is lean on the fender and you know it's too stiff. I told him it was too stiff but he's one of those people who automatically rejects what other people say. Big tires, big hemi and mid 9's with a lousy leave. Yes, he's an ET chaser who couldn't win a round to save his life.

Springs are cheep. I'd start at 200# on the front and 110# on the back. And adjust the fronts softer once just to see if it helps lol.
It looks to me like you can go to a longer front spring but it might be camera angle.

I didn't even watch the video (sorry at work), but I am sure the front shocks are too loose. I have the same AFCO DA's, I'm 300lbs nose heavy on a 116" wheelbase, and mine are STILL almost full tight.

Got some 200 lb springs one the way, I started full tight when i first ran the car and it spun hard, I made two click increments and got a little better each run but still would chatter the tires and its full loose now which i did get the best ever 60foot but i know there is a lot more there to get.

I appreciate everyone's input! My goal is to get a consistent low 9.50s and I'm close.

You may need to go as low as 85# on the springs, if your Dart is light in the back. I did. A ladderbar car like mine needs a ton of shock control on extension. You are probably close, if you have a three speed tranny or stick. No expert on the subject here, but I would think a soft spring rate allows the shocks to do their job best, which is steady application of rear axle speed.

I'm definitely no expert which is why I'm always askin for help here, What I have a hard time wrapping my mind around is it use to pick the front up and stick the tires with the 6 banger torsion bars and calvert 90/10 shocks. I did nothing to the rear and with setting the ride height in the front and adjusting the shocks as instructed by AFCO, I went from stiff to completely loose in the front and still seems like it needs to rotate a little higher to plant the rears. I have lighter front springs on the way but I cant understand why I may need lighter rear springs but i'll try anything to get it to hook like it use to. Keep the advise coming , I have thick skin so keep em cumin!

It's all about stored energy and getting a balance front and rear.

Your /6 T-bars had plenty of stored energy, the front springs now have less I guess.

Going lighter in the rear is adding stored energy. This helps drive the tire down at launch

Most likely your 6 cylinder bars were a lower spring rate than your current 250 front springs. To get the proper ride height the adjusters were twsited to compress the bar. Energy stored in a spring or torsion bar dimenishes as it is unloaded. For instance a 250/" spring compressed 2" will support 500lbs. When it expands 2" all its energy has been expended. A 125/" torsion bar will support 500lbs when it it tightened the equivent of 4". After unloading the torsion bar 2" just like the spring you still have 250lbs of stored energy (125×2=250). That stored energy helps lift the front end. For the rear the lighter spring will have to be compressed further to maintain the same ride height. Then as the housing separates from the body that energy will aid in loading the tire for a greater amount of housing travel.
Doug

get a pict of your front spring set up Mike... seemed to me at the ride height you were at, the spring seats were moved up quite a ways on the shock (spring compressed).

Scroll up J, I posted pix of the fronts and rears earlier.

That's why I suggested a longer spring

Chattering the tires leads me to believe you may need more air pressure in them

ok! updated my score card.... carry on!

Cab, I started at 14 and foot braking it spun bad, Adjusted the front shocks and took the pressure to 11 and still sun but not as much. Adjusted the shocks again and got a little better but was chattering the tires. I finally adjusted it full loose in the front and full loose in the rear and too the tires to 10 and it got the best 60 foot 1.35 but still chattered. I really don't think I'm far off but need a little something to get it to stick. One of the things I'm thinking of is pulling the stop and see if it will give it that much more front lift to get that little extra?

That makes sense,

I'm in the same boat, i'v installed the the Bob's frontend kit with afco's and 250 lbs springs and can't seem to get it to hook, I use to 60' anywhere from 128-29's to now just 132 with the afco's/250 springs. Talk to bob a few weeks ago and he say to start loose on the shocks and foot break it, i went out last night and mange to get two pass in without much luck. I'll keep an eye on this thread let us know the outcome.

What exactly is or do you mean by "chattering" the tires.

The only video you have shown it seemed to leave fine. So without seeing what it is doing, it is hard to diagnose an issue. I still don't think lack of front end travel has anything to do with the issue. If this car has enough power to go mid 9s, it needs very little front end travel.

And if you intend to use the trans brake, use it while sorting the car as well

What tire?

Tires shake or chatter is the only way I can describe it. It use to only do that when my slicks were going away but these are new, Hoosier 29.5 10.5 tread width is right at 11.2 across. I do intend on using the brake on the next outing. With all the new changes to the car I've only used the brake once and it spun pretty bad so I've been footbraking it to sort the front. I still only have about ten runs on the new combo.

IMO better video will help a lot here..

My question is what are you trying to accomplish? Best footbrake launch or planning on using the transbrake? IMO if you plan to run the car on the brake all this stuff footbraking is kinda useless IMO. If the goal is to make it the best it can be while on the brake then why even bother with how it works footbraking, or are you looking to run a class where you have to footbrake it? Even if you do find a way to make it work decent footbraking all that may be totally useless using the brake.

Generally speaking on the brake it should take little front end movement to get the car to hook, on a footbrake IMO it will end up taking a great deal more travel up front to work..But that is just a guess. IMO from what I saw in the video was a decent working footbrake car. But that means little if you are not looking to footbrake it..Just seems counter productive to worry about how the car leaves footbraking if that is not the intention.

Thanks Al, my plan is to run c gas or 9.60 class. Last outing was purely to get the the front end sorted out and would spin just footbraking it. Towards the end it was getting better but even having the chip at 3000 would blow the tires on the hit.

Launch critique??...I'd say you tree'd me with a red light...

Sorry Mike, couldn't resist

I've found mine generally chatters the tires before it's on the verge of full spin. My car weighs 1830F/1510R, 113"wb, 125 lb rear springs. It has run either 10.5x29.5 or 10.5x31 M/T's. Mid 1.2x-low 1.3x 60 ft on the foot brake. In my case it took raising the ladder bar to gain some separation to apply enough load on the tire. As Dizuster stated with his I also run the front rebound close to full tight. Adjust for track conditions with the rear rebound. When it gets greasy loosening will keep the 60ft spread closer from best to worse. When it gets goo, tighten them up and it'll go quicker yet.
Doug

[quote=MoParFish]
Launch critique??...I'd say you tree'd me with a red light...

Sorry Mike, couldn't resist

Funny, thats the next thread, how to slow down my reaction

NO, it didn't. I don't even have to see it to know that is not even remotely possible. Your car will NOT blow the tire off at the hit. Now it might shortly after because it is crushing the tire, or topping the front and THEN spinning. But it is NOT doing it at the hit of the throttle.

The reason I asked about the "chatter" was to see if you described it as a shake. Tire shake is caused by too much bite and or not enough wheel speed

The video was with it footbraking, I didn't have a vid, with the transbrake launch. Transbrake 60 foot was 1.51 and spun instantly, I only have one hit with the brake so far. As Al Mentioned I need to sort the issues using the brake I just havn't because its not hooking just footbraking.

You need to quick footbracking the car and start working on how to get it happy on the brake. C/Gas being a .400 Pro Tree deal will require you to run it on the brake. So quit trying to get it to work footbraking. Just putting laps on the motor and making no progress.

As Monte pointed out I highly doubt it is blowing them off at the hit. Likely just after that when the suspension is being upset. Those front shocks have VERY little front travel,nature of the beast. Having said that you should be able to get them to work but they do likely only have 3" or so of travel is my guess. Applying power to get the wheelspeed up will help with the shake and pitch rotation most likely. Also don't be afraid to go DOWN with the tire pressure.

What we are trying to tell you is that NOTHING, not even a fuel car spins instantly at the hit. It's what happens AFTER the hit that matters.

That shock may only have 3" of travel, but that's plenty at the wheel and that is where it matters.

If it shakes the tire, that generally means it is hitting the tire TOO hard. Ways to fix that are tighter shocks on extension, both front and rear. More power or lower the tire pressure

What he said

for this, didn't want it to fall off, any up to date news on this.

waiting for springs, I'm looking for a TNT close to me before November, There's a Chevy race on the schedule that has an open lane, Might put a Nova badge on it & jump in their party. I get this thing to hook in good air it should get me in the low 50's or better

We call it SCSN, or Street Car, or Streetcar Supernationals

Man I wish I could do that race, Don't have the vacation time and cant afford the trip right now

Mike Cunningham will be there to win the non E "again" and wish I could at least go to support him and watch. have try to do something local. Good luck AL!!, I will be at least watching you guys on Bangshift!

We actually will not be running there this year at all. Well maybe the dragster but not sure honestly.

So what spring did you decide on? I believe you had the 250 on the front correct? Or were you changing the rear?

Ordered 200 lb fronts and 110 rears, going to change the fronts at home and set ride height and that's the only change I want to do for the first hits. If it hooks i'll leave it. if not i'll change the rears at the track.

There is a race in Fontana next weekend. Free test and tune on Friday. A few Moparts members are usually there. NMCA West race, track prep is usually good as long as it is not 100+ degrees should be good. Plenty of classes and lots of opportunities to put laps on a car. Many of the bracket guys double dip at least.

Don't assume that changing front spring rate is gonna be the magic ticket. IMO some good video would help a lot. No reason you cannot get it to work but might need some more changes. Don't forget the converter as part of this package, you might need more stall speed to take some of the aggressiveness away at the hit....

Noted Al, I had the converter adjusted with the Dyno sheet by A-1 which Is what my converter is, Jason recommended them and they adjusted it from 5600 to 6300 per dyno sheet. do you think its still too tight?

I need to give the springs a try, cheep enough test.

AHHHHH... so not only did we "increase" HP, change the front suspension, we did a huge converter change. .... the rest, of the story. personally I'd love to see what would have happened leaving the converter "as is".

I mentioned that somewhere deep in page one J. Thats next on my agenda, to call A-1

well I'm a small block guy so I'm a bit slow.... My 60 changed quite a bit going from 5800 to 6200. Definitely didn't get up on the tire like the lower stall one did. I didn't experience loss of traction with the stall increase, but loss of performance was definitely noted.... unless you are talking strictly bracket stuff because the 1.34 60 times pretty much every hit made the car very predictable. Our last visit to Famoso I ran my best ET to date Sunday am and that definitely wasn't "good" air. That's with the "other" converter I bought that is tighter. Dave also noted it was definitely up on the tire over our March Meet passes. Think data from that weekend we're around 1300 DA. Can't say this is your issue.... but I sure wish you'd kept the old converter and could throw it in for a weekend.

I'll this again to see if any updates?

Plan to run on the fifth of November(Super Chevy race)
I'll update !

I`ll see where things are in my world and maybe roll out to race w/you guys...........

Cool

Ok had a rough week but changed my front springs,loaded up and went to Famoso.
Left the front shocks as they were. Full loose on extension, rear shocks were set at 3 which is in the middle. Slicks set at 12lbs. Got only one run and was the best yet but again it spun. The hit was with the brake and 3400 chip. That was the tenth run on all the new changes and creeping forward but the car will not rotate. It's comes up and as soon as it starts to pull the front, it starts spinning. I couldn't stick around because I was supposed to be at my wife's birthday so I attempted a second run but the car died on the line and didn't refire.r really feel like scrapping the high dollar front end and going back to stock

Good Job, what is Your finish line rpm?

You have answered your own problem right it this part of the text. Tighten the front rebound.
Doug

Yep I agree, Stated that at the beginning of this thread, fell on deaf ears I guess, but sometimes it is hard to remember every ones post. Try it Tighter next time out and work on the rear separation as stated.

[quote=Dduster]Good Job, what is Your finish line rpm? [/quot

Crossed @ 7800

Full loose is NOT gonna work

Thank You

That was the tenth run on all the new changes and creeping forward but the car will not rotate. It's comes up and as soon as it starts to pull the front, it starts spinning. I couldn't stick around because I was supposed to be at my wife's birthday so I attempted a second run but the car died on the line and didn't refire.r really feel like scrapping the high dollar front end and going back to stock rolleyes

Hang in there champ,don't throw in the flag yet. I've been following this thread for a while now. Cause I'm having similar problems(transferring weight)talk to Bob about a month ago and he recommend sending in the shocks for revalveing. Hope this works for me one thing I will say bout this setup is it makes pulling the pan/headers easy and it goes straight. I had a best of 1.29 this year with this setup and that's with the shocks set full loose it still seems to tight for me. My plans over the winter is to pull the shocks and send them out.

When you get ready to scrap that high dollar front end, I will be glad to take that junk, because that definitely is NOT the problem.

People get SO caught up in the posts on THIS site, about "it's got to have 5" or more of travel, or it won't work" that they can't see the forest for the trees.

Another thing, if it has the fronts off the ground.....it IS transferring and it IS rotating. Not sure what else you think it's supposed to do

Video dizuster posted acouple months ago it may beable to shed some light on your issues
https://youtu.be/sjZDXBXRC9Q

Monte you have a PM

I would agree to tighten up the front. The rear may need a better shock or increased rear valving. Video is always best