High speed stability issues

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I agree with more air in the slicks.
So when your at the top of the track and it gets your attention! Does it feel like the rear is getting loose or that the front is not responding to your steering input.
If the tail is wagging put more air in the slicks(13-14 psi) and if that helps but don't fix it. add some weight to the trunk and see what happens.

I think getting the air from under the car(front air dam) is the answer.
If your fiber glass hood has a crack in it, at 130 mph, your going to loose it. BUT its not the problem.
Just my logic or .02
 
I haven't read all the post so forgive me if someone posted this already. If the scoop isn't sealed to the carb you are getting a lot of air under the car and that will lift it. Seal the carb and get a boost in performance and keep the air out from under. Put a spoiler on it also. On the alignment put in 5 degree caster if possible camber 0 and toe about 1/16 in.
 
On my 66 Dart, I was having an instability problem at the top end, the car was good when first put together but became worse over the years. Car was squirrly at over 100 mph, the faster it went the squirrlier it became (trapped at 125 to 126 mph), but when I let off it would straighten out. The front suspension was basically stock except for poly bushings in upper and lower arms, new ball joints, tie rods, and adjustable strut rods. It had 1.5 to 2 degrees of caster, 0 camber, and an 1/8" toe( best I could do with stock parts). Three years ago I put QA1 upper a arms, new lower ball joints and larger C-body tie rod ends and the shorter A-body sleeves, and idler arm, and set the alignment like LO23M8B said. This made the steering much more responsive which cured around 90% of the problem. After that I could feel that what was left of the instability was the back of the car swaying around. I went from a 9x26 Hoosier slicks to M/T 9x28st slicks, stiff sidewall manual trans slicks (my Dart is a stick car). A few adjustments to the Cal-Trac bars and the Dart is going straight and stable again.
 
Is your steering box worn?
My old charger got real loose on the top & found my steering box was starting to wander
 
19DART66 said:
On my 66 Dart, I was having an instability problem at the top end, the car was good when first put together but became worse over the years. Car was squirrly at over 100 mph, the faster it went the squirrlier it became (trapped at 125 to 126 mph), but when I let off it would straighten out. The front suspension was basically stock except for poly bushings in upper and lower arms, new ball joints, tie rods, and adjustable strut rods. It had 1.5 to 2 degrees of caster, 0 camber, and an 1/8" toe( best I could do with stock parts). Three years ago I put QA1 upper a arms, new lower ball joints and larger C-body tie rod ends and the shorter A-body sleeves, and idler arm, and set the alignment like LO23M8B said. This made the steering much more responsive which cured around 90% of the problem. After that I could feel that what was left of the instability was the back of the car swaying around. I went from a 9x26 Hoosier slicks to M/T 9x28st slicks, stiff sidewall manual trans slicks (my Dart is a stick car). A few adjustments to the Cal-Trac bars and the Dart is going straight and stable again.
Click to expand...
Thank You
 
Here's that alignment sheet.

1626214515418663080312189787325.jpg
 
I was having a similar issue with my Dart (much slower). When I lifted after the traps she would wander. Not scared for my life wander but definitely got my attention. I solved the issue by lifting more gradually. Good luck...
 
I have considered adding a front lower shield. There is no lower air pan under my radiator. I see a few on ebay. I can fabricate something from the lower edge of the front bumper to the k frame. Do you think I should?
 
66Valiant528 said:
Here's that alignment sheet.

View attachment 1715764635
Click to expand...
I had an all stock front end and very stable at 118 mph.
Good strut rod bushings if using stock. I followed the old mopar chassis book. Plot your toe change( bump steer), I had to tilt both my idler and my steering box to minimize toe change.
After that I went to an alignment shop and had the front end set to 1/16 toe in, 2-3 degrees caster with an aftermarket eccentric bushing kit, but the main thing is I had these setting set with me sitting in the car with the front end jacked up 1 inch from ride height to simulate at speed. Car used to run 11:20 at 118 and I practically never had to move the steering wheel.
 
I used to have a similar issue when I had mixed bias-ply slicks and radial front tires. It make the nose of the car hunt at high speed and the back of the car wag. I switched to Hoosier drag radials quite a few years ago and kept the front radials...now the car is very stable at about ~131mph.
 
66Valiant528 said:
It was bad. The jersey barriers were flying by and close . I do believe that the scoop is pling the hood up as I have developed a crack at the peak of my glass hood. I have picked up a steel factory hood. I think a cowel scoop makes sense. I asked Harwood about an open rear scoop. They told me I can drill holes in the back of the scoop to let air pass through. That's a cheaper option! Just not sure if it'll do anything. I may try to do some sort of pan underneath. It'll be tough to fabricate and mount. Hoe about lifting the rear of the hood or punching vents in the rear?
Click to expand...

randys spoilers --------------how many hood pins / at that speed , u need more than 4-6--------toe in ??
 
I have 2 tongues at the back of the hood that slide into slots cut at the base of the cowel. 2 hood pins up front and 6 Dzues fasteners (3 per side) up along the fenders. Ya a couple more pins in the front certainly wouldn't hurt. Hoosier tires all around. There skinny front runners 4.5 by 26 up front and full slicks in the rear.
 
When are you going to try some of these things?

Just curious. We've made many suggestions, I'd like to know what works.

:)
 
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The weather has been bad here in New England. It's 90 miles to Epping and 132 to Lebanon Valley so I need some good weather before I load up. Soon I hope.
 
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