Southside machine lift bars and unloading the tires

That is what I was thinking, I have some good nylon round stock here that I can make some washers from. The big thing is to make sure the bushings are moving freely so I'll have a look this weekend.

BigRigTech wrote:That is what I was thinking, I have some good nylon round stock here that I can make some washers from. The big thing is to make sure the bushings are moving freely so I'll have a look this weekend.

I looked around and found the bag of spares that I purchased from SSM back in 2000. I have 7 of the washers. I measured them and found that they are 1.375" outside diameter, 0.75" inside diameter, and .0140-.0145" in thickness. They are really thin!
Gary

Awesome, thanks for the info. I'll see if the machinist at work can make some for me.

I think that you are on the right track to make sure there is no binding issues.  Another thing to consider as already mentioned is hitting the tires to hard and fast. With Big Block torque and new converter the rear tires can be driven down so hard they rebound like a basketball and it happens faster than the front end can react. Then the tires unload and the hole process cycles again and again (porpoising) until it diminishes and goes away. This is common as we add more and more power without upgrading the suspension. If we take a look at chassis evaluation as it pertains to the Instant Centers. let us start with slapper bars ----- the IC is the distance from the axle center line to the snubber that slaps the leaf spring ----- length is normally in the 26 to 29 inch area and as power increased  there was a need for improvement. Then along came ladder bars with IC length in the 32 to 36 inch area (axle center line to front bolt) and as power increasing the 4 link was developed with adjustable IC lengths that usually fall in the 40 to 60 inch area. As the IC length increases it softens and slows down the tire hit and coordinates with front end lift.

  Now how does this apply to the real world? If we consider the coordination of rear tire plant and front end lift to maximize weight transfer it becomes a little easier. If the rear tires are hitting to hard what can be done if we are not going to change the suspension.
    REAR END
      Stiffen rear shocks (rebound or extension)
      Add more tire pressure ( to reduce basketball effect )
      Add rear ballast 100 lbs as far back as possible ( this adds rear weight and subtracts front weight --- Think about it --- don't worry about the weight --- if this stops the tire unloading the car will be faster)    

    FRONT END
   Check Front suspension for binding and freedom of movement  
   Front Shocks ( something like 90/10 -- 80/20 -- 70/30 valving)
   Front Springs ( softer spring that will still hold the car up to proper ride height --- for stored energy )

 Hope there is something hear you can use.

One more very critical thing I forgot to mention is PINION ANGLE. As the rear end goes through its travel the pinion angle must NEVER go negative.The angel between the drive line and and pinion must always have some down angle. If it goes past center the pinion will snap back down -- unload the tires and here we go again with wheel hop as it travels back and forth through down angel to up angel. This should be one of the first things to check on your list.

pinion angle...............in all honesty is about making the u joints happy, if your seeing results from changing pinion angle its more likely the changing the angle of the bars etc that's producing the result.

I see too many get up in the "pinion angle" numbers when it really the geometry of the bars that's producing the changes.

The ujoints have to be happy though.

richter69 wrote:pinion angle...............in all honesty is about making the u joints happy, if your seeing results from changing pinion angle its more likely the changing the  angle of the bars etc that's producing the result.

I see too many get up in the "pinion angle" numbers when it really the geometry of the bars that's producing the changes.

The ujoints have to be happy though.

Yep

I checked my pinion angle when I fit the 460 and C6 in there, I don't remember the numbers but they were all in the correct range. I'll free up the bars, soften the shocks and play with tire pressures. I'll post my findings.

The videos would be 100% better if shot a lot closer to the car next time.  

But from what I can see it kinda looks IMO like it's a little down on power after the initial hit. It's got enough at-launch torque to cause a decent amount of initial rear suspension separation (the initial hit) to smack the sidewalls with. But there might not be enough torque/power to continue keeping the tires planted (after the initial hit happens) as the launch continues on. And after the initial hit the whole car (esp the front) does look kind stiff going down the track. Kinda like if the springs were too stiff, (or too soft & were adjusted way up enough to stack solid), or like something might be binding somewhere. You might think about checking the rear suspension for any binding during full suspension travel (like rear shocks hitting the housing, or bent components, etc, etc). And if the car currently has no suspension binding happening, and also has little/no body-roll happening during the launch, it might not currently have enough power on tap to really need an anti-roll at this time.  

Making the rear shock extension valving looser will probably cause a greater amount of initial rear suspension separation to happen at a faster/quicker rate (a harder initial hit). Doing this might help, or it might hurt by causing a greater amount of spin/bounce to happen (after the initial hit) as the sidewall unwinds/rebounds from the increased amount of initial hit.

I would check the whole car for any possible suspension binding during the full suspension travel, make sure the front/rear spring rates aren't too stiff/soft, get the cheap Strange adjustable front struts, and also try a stiffer rear shock extension valving during TnT to compare to a loose setting.

I'll try a bunch of stuff at the TNT next Friday night . I'm going to take the bars off to check the bushings this week for being stuck.

Your going to end up changing the front struts and rear lowers.

I are what we can do with what I have and if nothing works I'll make some changes next winter.

I checked out the SSM bushings and greased them, everything is moving freely and everything took grease easily so I don't think anything is binding. I set body on stand and worked the axle up and down several times with my air operated floor jack.

Just way too much antisquat and too short and high of an IC to work effectively with any amount of power.

468 with 685 hp. 4500 stall c-4 airbags with 20 lbs to clear 28 tires 1.45 with 3000 launch in 1983 mustang convertible 10.51 short shifting

whatbumper wrote:Just way too much antisquat and too short and high of an IC to work effectively with any amount of power.

I guess Im an exception to the rule lol.

I know there are a couple other Mustangs racing down there with the same bars so I'm going to chat with one of them that I know. He has a 351C in his 81 Capri with a glide, been this way for a LONG time running 10.30's.

richter69 wrote:

whatbumper wrote:Just way too much antisquat and too short and high of an IC to work effectively with any amount of power.

I guess Im an exception to the rule lol.

That rule doesn't apply to cars with the air cleaner sticking through the hood. Lol

ditched the air cleaner, its got one of them ugly ass lexan deals now...............

richter69 wrote:ditched the air cleaner, its got one of them ugly ass lexan deals now...............

Pics for proof

tonight

We seemed to lesson a lot of the dreaded bounce. Shocks set on 4, slicks at 11psi and longer burn outs turned it to a much smother launch than last time out and I can feel it in the seat of my pants too...LOL:D 

https://www.youtube.com/watch?v=5fJE49zebiU

They are junk I tell ya.......

richter69 wrote:They are junk I tell ya.......

Its the kitchen strainer that makes it fast......  

maybe you should try one........