famous bob
mopar misfit
I wonder if a high h.p street car would be better off w/ a soft hit to start with, especially w/ a smaller 275/60/15 drag radial. and will going to a larger drag radial need to have the setting changed , generally speaking .
Caltrac Tuning Info LOOK HERE
- Thread starter mshred
- Start date
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RockinRobin
Well-Known Member
After fighting with inconsistent launches I decided to move the CalTracs on my '70 Duster drag car to the upper holes in front. I had to take the cutoff wheel to the front spring brackets to allow enough clearance for the bolt heads of the CalTrac through-bolts. Upon inspection I discovered that the leaf spring shackles were for a B or E body and appeared to be binding, so I replaced those with the correct A-Body ones. The drivers side shock tang on the spring plate was also bent upwards about 30 degrees, so I straightened that out on a shop press. Also had to replace several U-bolts that were stripped. I probably should have replaced the other 2 at the time but didn't.
Calvert said to start off with about 1/4 turn of preload and put the Calvert 9 way shocks (Rancho) on 8 since I footbrake. They said if it spins about 30 or 40 feet out to go UP on the shock number! Well, starting on 8 didn't leave me much room for adjustability so I started at 7 and hoped for the best.
We took it to TNT Friday to a moderately prepped track full of street cars. I figured if it would hook after the street cars pulled up whatever prep was there it should be okay for a well prepped track on race days. It seems to be hooking well after going up to about a full turn of preload and no change on the shocks. I see a little bounce down the track, but that may be the 1st to 2nd shift causing that. Back end seems real stiff but if it works I'm fine with it.
60' and overall numbers were a little low but it was very hot/humid and it ran very rich the whole night. The DA's were in the 3300-3500 range, compared to less that 1000 last weekend! Going to take it out again this Friday in prep for Saturday's race and see if we have it set right.
Calvert said to start off with about 1/4 turn of preload and put the Calvert 9 way shocks (Rancho) on 8 since I footbrake. They said if it spins about 30 or 40 feet out to go UP on the shock number! Well, starting on 8 didn't leave me much room for adjustability so I started at 7 and hoped for the best.
We took it to TNT Friday to a moderately prepped track full of street cars. I figured if it would hook after the street cars pulled up whatever prep was there it should be okay for a well prepped track on race days. It seems to be hooking well after going up to about a full turn of preload and no change on the shocks. I see a little bounce down the track, but that may be the 1st to 2nd shift causing that. Back end seems real stiff but if it works I'm fine with it.
60' and overall numbers were a little low but it was very hot/humid and it ran very rich the whole night. The DA's were in the 3300-3500 range, compared to less that 1000 last weekend! Going to take it out again this Friday in prep for Saturday's race and see if we have it set right.
RockinRobin
Well-Known Member
Got another 4 passes Friday night, and did slo mo video of the launch. Now I know why the 60' are off by about .05:
Looks like it's hitting the tires pretty hard. The car hooks for about 1/2 of a tire revolution, then spins about 2 turns or so, then hooks up again. Trying to figure out what to adjust to get it to stay on the tire.
Shocks are currently at #6, so can go either way with those, tire pressure is at 13.5
Looks like it's hitting the tires pretty hard. The car hooks for about 1/2 of a tire revolution, then spins about 2 turns or so, then hooks up again. Trying to figure out what to adjust to get it to stay on the tire.
Shocks are currently at #6, so can go either way with those, tire pressure is at 13.5
Transbrake?
RockinRobin
Well-Known Member
Sorry, forgot to say footbrake leaving off idle.
Now this is what worked for my car 4 for foot brake and 2 for transbrake.
RockinRobin
Well-Known Member
What worked?
Yes but once again this is my car so might be different. But the rancho setting click in the rear for a footbrake was click #4. My car weighs 3000#'s down the track, stock front suspension, 90/10 shocks up front 29" x 10 slicks. Mono leaf in the rear that is 1" lower than stock. high nine second car 9.80's
RockinRobin
Well-Known Member
Sounds pretty similar I might be 200 lbs lighter and 29" x 12" slicks. Ranchos are at #6 right now maybe I should try a click or two lower.
360tripleblack7
Gold Member
Hi Folks,
Finally I could test my new set of Viking DA Shocks that I installed in my car. These shocks already improve my 60ft from 1.58 to 1.54 but I'm still having tire bouncing on the start.
I'm using this setup on the Shocks:
Front: Compression = 12, Rebound 2.
Rear: Compression = 4, Rebound 12.
My car is an A Body, 3300lbs Small Block with 464WHP, Footbrake, 4500 Stall Converter, Hoosiers 28x10.5, 4.56 Gear, Leaf Springs with Assassin Traction Bars.
I'm sending two videos of the start... So if someone could see that and can support me to fix this issue will be great.
I think that I'm having same problems that MrHotRod had with his car...
Thanks...
racerhog
RacerHog likes his Mopars
Looks to me like its bouncing on the sidewalls... I dont see much motion between the body and the diff. when it leaves. So my suspicion is its the flex in the side wall of the tire.
I would try a couple less pounds of air in the tire, and see that help the problem. I would go 9psi and work my way down to no more than 6psi.
Just my 2 cents
I would try a couple less pounds of air in the tire, and see that help the problem. I would go 9psi and work my way down to no more than 6psi.
Just my 2 cents
RockinRobin
Well-Known Member
My car did the same thing, bounced like that until I put more air in the tires and loosened the rear shocks to make it stay on the tire. It liked 13 lbs. in the slicks and #3 setting on the Rancho shocks. My car is about 500 lbs lighter than yours.
RockinRobin
Well-Known Member
OK, so I moved the Ranchos down to #4, no difference, then moved them to #2 and It's hooking better:
I was able to use this setup to win the race on June 17th, but it still doesn't hook consistently in the left lane. Fortunately this track allows you to put 2 dial ins on the window, 1 for left lane and 1 for right. I bought a pair of 2 degree shims and I'm going to give them a try at the next test-n-tune night.
dadodgekid
When in doubt... floor it
one thing ive learned with my cals, 275/60 radial setup... my tire worked best with 18Lbs of air and 50/50 on my rear shocks. and less and the car would bounce, sorta a WAwaWAwaWA effect...( say it too yourself like an engine!) lol
RockinRobin
Well-Known Member
Thanks, but, Radials vs slicks = apple vs oranges. Normal pressure is 13.5 lbs. I tried it at 17lbs and all it did was spin. Tried lowering to 12 lbs. and it hooked a little better (.03 better 60 ft.) but still spun a little. It spun at the exact same time, so I felt like tire pressure was a band aid on the problem and not a cure.
dadodgekid
When in doubt... floor it
What hole do you have the cal trac in? Front bracket
RockinRobin
Well-Known Member
Msg #77 gives all the details.
I run my 315/60 M/T Drag Radials most of the time because it is over a tenth faster on them in the 1/8. It hooks most of the time. But I have a set of really old M/T 29.5/10.5 slicks that are probably 15 years old mounted on another set of wheels. When I run them I don't even have to do a burn out. It has never spun with the old slicks. I am running home made Caltracs with stock leaf springs. They are in the top hole with no preload ( just touching) and my Rancho shocks set on 9.
duster44d
Well-Known Member
With the caltracs is it better to use a pinion snubber or better to go without a pinion snubber?
ProSport
Well-Known Member
No pinion snubber with caltracs.
duster44d
Well-Known Member
Where did you get your Heim'd front struts ? How much?
I wanted to use them, but the one's I was looking at were pretty spendy. ($200 ea?)
Having issues with my setup. Tired of fighting it blind, so maybe someone here can help. It’s unloading the tires and bouncing as the front end almost comes off the ground. It’s been spinning all day, so I decided to start over with the bars in the top hole, 3/4 turn pre load, shocks at 10, 12.5 psi in the tires, and launching off the transbrake at 3500. I have a feeling the QA1 shocks I put on are the problem, but I don’t want to just throw money at it if I can make it work.
I take it has never acted this way?
Ok, first off, eliminate the use of the 2step for the time being. It is exasperating the issue.
It looks like you're running out of shock travel on the rear.
How many runs on those tires? I've seen tires hook good, then get at the edge and never hook again. Even with indicators left.
I've heard the guys in Div6 take care of the surface up there, that still true? How do you feel about the track? I don't see a lot of gloss.. no VHT?
BTW, love the car.
Ok, first off, eliminate the use of the 2step for the time being. It is exasperating the issue.
It looks like you're running out of shock travel on the rear.
How many runs on those tires? I've seen tires hook good, then get at the edge and never hook again. Even with indicators left.
I've heard the guys in Div6 take care of the surface up there, that still true? How do you feel about the track? I don't see a lot of gloss.. no VHT?
BTW, love the car.
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