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Discussion Starter · #1 ·
Not sure I'm in the right forum section for this. Finally got the 33 Willys into the nines on the 1/4 mile but it is pulling to the right until just past the 1/8 mile. Running 14.5 lbs in left rear and 15 lbs in right rear. It has a 3 link rear. It's not real bad but not going straight.
Blown 434, TH400, 9" Ford, 4:11, 29.5 MT drag radials, 2464 lbs.
Any ideas?
 

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Have you measured the circumference of each tire? Does the rear diff have a spool in it? A friend with a 7 second 1/4 mile 1966 Nova on 10.5 slicks, he would fine tune his car with 4 link with a 1/2 turn on 1 of the four links to dial in how straight the car ran , how equal it carried the front tires off the surface
 

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You need to do a couple of things. I would check the straightness of the rear axle. You can use a plumb bob and string to drop marks on the garage floor using masking tape and a pen. I would drop one from both sides of the brake drum or disc rotor and do this on both sides of the car. Ideally the measurements from one side of the rear to the other should be exactly equal. Anything more than a 1/16" could be a problem. With that done and the rear is okay, you should triangulate the car to make sure it is square. You find the center of the car between the front spindles, then measure back to an identical point on each side of the rear - I normally like to drop new marks from the center of the axles. It is also a good idea to make yourself a drawing and write down the measurements - if you ever do it again you will have reference information.
 

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Discussion Starter · #4 ·
Have you measured the circumference of each tire? Does the rear diff have a spool in it? A friend with a 7 second 1/4 mile 1966 Nova on 10.5 slicks, he would fine tune his car with 4 link with a 1/2 turn on 1 of the four links to dial in how straight the car ran , how equal it carried the front tires off the surface
Haven't measured the tires, It is a spool, It's a 3 link.
 

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Get a buddy or two.

Have them take videos of the thing leaving. From the drivers and passenger sides.

Compare at slow frame rate.

Look at the entire car as it leaves to see if one side is compressing or unloading (body to tire) before the other.

After checking go and make adjustments writing down those adjustments then taking more videos of both sides.
 

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It's not pulling to the right, it is pushing to the right.....the rear left side tire has more traction, or more circumference.
Only a front wheel drive car could pull to one side under power ..... a rear drive car you are being pushed off course by the opposite side rear tire having more traction or more roll-out.

Why are you running less pressure on the left rear??

i'll second the plan Chasracer put forth...make sure the car/axle is square first thing.
 

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Discussion Starter · #7 ·
It's not pulling to the right, it is pushing to the right.....the rear left side tire has more traction, or more circumference.
Only a front wheel drive car could pull to one side under power ..... a rear drive car you are being pushed off course by the opposite side rear tire having more traction or more roll-out.

Why are you running less pressure on the left rear??

i'll second the plan Chasracer put forth...make sure the car/axle is square first thing.
I was hoping the different tire pressures would help the problem. It pulls the left front wheel pretty good.

I'll be doing what Chasracer said to do.
 

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I was hoping the different tire pressures would help the problem. It pulls the left front wheel pretty good.

I'll be doing what Chasracer said to do.
If anything due to tire pressure changing hook were to be done, have lower pressure on the right to increase traction to counteract the left side drive tire from pushing. Opposite of what you have now.

Don't try to use tire pressure to control body roll.....for that you need an anti-roll bar(or a 4 link to add preload). (You mentioned pulling the drivers front hard).
With the 3-link, you really need a rear anti-roll bar. You've got no other correct way to deal with chassis roll with that 3 link.


Tire pressures are only adjusted to influence hook, not chassis reaction.

this is all after checking the chassis for square of course.
 

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You are dealing with the effect. You need to be looking at the cause.




Video is the best way I know of to tell you whats doing what when and why.
It takes runs, cameras, adjustments, and comparing those adjustments to your previous results(in your notebook).



Lets say you have a bushing with some slop in it. Your butt sensor may not pickup on that and the thing may not be noticeable when at rest or on a lift. It is only when the suspension is unloaded or the body twist at "this" angle that the bushing allows that one tire to drop further then the other.

A camera mounted at the transmission cross member pointing forward will show you when your tires are lifting. You will see the bulges decrease and maybe a bit of daylight as that front is unloaded. If you have say the passenger side coming up noticable faster then the drivers then the question of why comes into play. When the car is loaded as it comes back down you may see one of the tires shimmy. Why is that? Whats going on? Now I am talking about watching frame by frame slow video here and over a few runs to eliminate the chance that you did something in one run diffrent then the other.

But it is one of those things where once you use a video you can see oh yea that control arm is hitting different then the other I wonder why that is. Inspection revels something like the bushing is cracked or a hole has become elongated .


You can chase "it might be's" (potentially making things worse) or find out what it is by adding a new way to record data then making sound decisions based on that data before comparing your results.
 

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Discussion Starter · #10 ·
If anything due to tire pressure changing hook were to be done, have lower pressure on the right to increase traction to counteract the left side drive tire from pushing. Opposite of what you have now.

Don't try to use tire pressure to control body roll.....for that you need an anti-roll bar(or a 4 link to add preload). (You mentioned pulling the drivers front hard).
With the 3-link, you really need a rear anti-roll bar. You've got no other correct way to deal with chassis roll with that 3 link.


Tire pressures are only adjusted to influence hook, not chassis reaction.

this is all after checking the chassis for square of course.
Thanks for the tire pressure tip. Could you expand on the anti-roll bar adjustment. We have a good heavy anti-roll bar and have lengthened the right side link by 1/2 turn but it is still dropping the right rear fender when leaving the line.
 

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Discussion Starter · #11 ·
You are dealing with the effect. You need to be looking at the cause.




Video is the best way I know of to tell you whats doing what when and why.
It takes runs, cameras, adjustments, and comparing those adjustments to your previous results(in your notebook).



Lets say you have a bushing with some slop in it. Your butt sensor may not pickup on that and the thing may not be noticeable when at rest or on a lift. It is only when the suspension is unloaded or the body twist at "this" angle that the bushing allows that one tire to drop further then the other.

A camera mounted at the transmission cross member pointing forward will show you when your tires are lifting. You will see the bulges decrease and maybe a bit of daylight as that front is unloaded. If you have say the passenger side coming up noticable faster then the drivers then the question of why comes into play. When the car is loaded as it comes back down you may see one of the tires shimmy. Why is that? Whats going on? Now I am talking about watching frame by frame slow video here and over a few runs to eliminate the chance that you did something in one run diffrent then the other.

But it is one of those things where once you use a video you can see oh yea that control arm is hitting different then the other I wonder why that is. Inspection revels something like the bushing is cracked or a hole has become elongated .


You can chase "it might be's" (potentially making things worse) or find out what it is by adding a new way to record data then making sound decisions based on that data before comparing your results.
Just happen to have a gopro I can put to use.
 

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Thanks for the tire pressure tip. Could you expand on the anti-roll bar adjustment. We have a good heavy anti-roll bar and have lengthened the right side link by 1/2 turn but it is still dropping the right rear fender when leaving the line.
wish I could point you in the correct direction, but the 3-link mucks up the works for me.....I'm only familiar with 4-link and anti-roll and it sounds like it either behaves different, or bad behavior is more pronounced because you can't preload one side with the 3-link itself like you can with a 4-link.
We leave the anti-roll bar set nuetral, and use the upper passenger 4-link bar for preload adjustment.

Just offhand, sounds like the 3 link doesn't give you enough antisquat, and it manifests the most on the passenger side.

It sucks that Billy Shope's suspension site is gone, there was specific 3-link info there. wish I would have know it was going to dissappear, I would have downloaded most of it.

If you can get a copy of "Doorslammers: The Chassis Book" by Dave Morgan there is a ton of info in there....I loaned my copy out and it hasn't come back.
 

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Discussion Starter · #13 ·
wish I could point you in the correct direction, but the 3-link mucks up the works for me.....I'm only familiar with 4-link and anti-roll and it sounds like it either behaves different, or bad behavior is more pronounced because you can't preload one side with the 3-link itself like you can with a 4-link.
We leave the anti-roll bar set nuetral, and use the upper passenger 4-link bar for preload adjustment.

Just offhand, sounds like the 3 link doesn't give you enough antisquat, and it manifests the most on the passenger side.

It sucks that Billy Shope's suspension site is gone, there was specific 3-link info there. wish I would have know it was going to dissappear, I would have downloaded most of it.

If you can get a copy of "Doorslammers: The Chassis Book" by Dave Morgan there is a ton of info in there....I loaned my copy out and it hasn't come back.
Thanks
I'll look for that book.
 

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Move the Right side lower link up 1/2" on the frame and see if it's better, don't change anything else.
If it gets better, there a couple small things to do to make it permanent.
 

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Discussion Starter · #17 ·
Move the Right side lower link up 1/2" on the frame and see if it's better, don't change anything else.
If it gets better, there a couple small things to do to make it permanent.
Are you saying to lengthen the link by 1/2" or to move the mount?
 

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What do you have for an anti-roll bar? Is it a true anti-roll bar designed for that purpose or a re-purposed sway bar?

I'm sue you know this, but the idea is that it keeps the frame from twisting in relation to the ground, but it sounds like yours isn't accomplishing that.
 

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Discussion Starter · #19 ·
It is a purpose built anti-roll bar and the frame does twist. I'll check the settings on the bar. What do you suggest for initial settings?
 

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Are you saying to lengthen the link by 1/2" or to move the mount?
Are the spring mounted behind the axle on your car?


Just raise the RR bar up on the frame mounted end a 1/2"- 3/4" depending how sensitive the chassis is. IE ridgity.
You can also move the axle end of the RR bar down but it more sensitive adjustment there so go 1/4"-1/2" if going that route.
My working theory is that the RR frame is dropping under load and moving the RR bar from level to the frame to down hill to the frame so it's adding rear steer(RR tire pushed rearward) AND unloading the tire.
Drive shaft torque also loads the LR so that compounding the problem and giving the LR more of the loads so the car is being pushed to the right. You didn't say this but the car probably settles down and goes straight enough once the initial launch happens (40'-60') and the chassis settles down because the RR bar is then level again or at least the same angle as the LR bar.
Moving the RR bar up a little counteracts the drive shaft torque and the pushes the RR frame back up removing the rear so the loads are more balanced left to right.
If moving the RR bar up isn't feasable than add 50 pounds to the RR spring rate or a spring rubber on the RR to see if your going in the right direction with spring rate.
 
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