[Fire Ball]

This is all new to me.., went from leaf springs to a 4 link..
I watched a bunch of Youtube videos and hit the search, I've learned about anti squat, instant center, pinion angle and center of gravity...

I put a string on the truck from the contact patch to the center of the front wheel, up about the cam shaft height.
I measured 58" forward from the center of the rear wheel, the anti squat line was 15.5" up.
WB 119.8"
Center of gravity is about 31"
I need to re-weigh it, but last time it was
FL 1209LBS 30.7% FR 1086LBS 27.6%
RL 799LBS 20.3% RR 845LBS 21.5%
Total with driver 3940LBS
About 1100HP to the tires
Mickey Thompson 315/60/15 Pro drag radials
Menscer double adjustable Afco shocks with 175lbs springs

Any help would much appreciated.

Thanks

 

[str8liner]

Where is your IC at? You should use an IC calculator, like Performance Trends or similar, or go to Baseline Suspensions and us the IC calculator they have on their website.

Instant Center Calculator for your drag car suspension

Calculate the instant center on your drag car suspension geometry.

www.baselinesuspensions.com

Put all the 4 link measurements in, so you have an idea where your IC is in relation to the CG and neutral line. All the other stuff is meaningless without it.

 

[Fire Ball]

Sweet, I’ll get out the tape measure tomorrow.
Thanks

 

[Fire Ball]

Got the tape out...

 

[str8liner]

Hey I think your CG is off.....31 inches? Is that right?

 

[Fire Ball]

It’s a pick up truck, I went with the center line of the cam shaft.. overhead cams.

 

[Fire Ball]

The crank center line is 18” add 6” like a push rod V8.
Makes the CG 24”

 

[str8liner]

The crank center line is 18” add 6” like a push rod V8.
Makes the CG 24”


View attachment 443663

That looks a little better. With a 31 in CGH I don't thing you could ever get above the neutral line to get some anti squat to hit those drag radials. Have you run it like this? Hopefully some drag radial guys will chime in. I never fooled with drag radial setups. Just slicks.

 

[Fire Ball]

Haven't run it yet, just had the 4 link installed a few weeks ago.

 

[Boosted Bullet]

Need get that AS up in the 130%-160% range. I would raise both bars in the front and see what that gets you. Can you post a pic of your brackets?

 

[Freakshow turbo54 ratrod]

the performance trends 4 link calculator is bad ass, also gives suggestions on where it needs to be. It took me a couple hrs to put in all the measurements but once it's done you can see all possibilities for bar angle.

 

[str8liner]

Need get that AS up in the 130%-160% range. I would raise both bars in the front and see what that gets you. Can you post a pic of your brackets?

That is what I was thinking but it looks like he still might not get much above 100 percent, if at all. Hopefully the uphill angle of the bottom bar helps it.

 

[Fire Ball]

Much Appreciated..
I can raise the bars up in the front., this setup is close to where I took the measurements.

 

[Boosted Bullet]

Nice setup. I would defintely drop the bottom bar to the lowest hole on the rear housing, and raise the front of the bottom bar at least one hole, and maybe 2 if you need to. If the top bar isn't already in the hole closest to the housing in the rear, put it there and see what the number is. May not have move the top bar in the front to get what you need, I hate when the spread starts getting real close together in the front. Even minor changes in ride height can change the anti squat quite a bit, so make sure it's where you want it.

 

[Fire Ball]

I put the upper arm in the hole closest to the rear housing and raised the front hole by 1
Lower arm I put the arm in the bottom hole and raised the front hole by 2
Im above the squat line.., is the instant center length too short?

 

[str8liner]

I don't know if I would worry too much about the length, so much as I would that bottom bar angle. Its running uphill 2.75 inches..... Maybe some guys that are familiar with them can comment on that. If you over do it sometimes its not good.

 

[000Racer]

I know of a guy in ultra street running 38" IC and 18" high with 111" wheel base on 275 radials.... You maybe in the ball
park with that, they are about 16-1700 hp though @ 3250 lbs.
With your longer WB you maybe good, and your damn heavy in the nose.

 

[mufflerguy]

I would try and get at least some weld on the inside edge of those 4 link brackets on the housing. I'm about 166% anti squat in my Chevy II. From the pic, it appears you'll want more lower bar angle. Up on front holes.

 

[Boosted Bullet]

Yes, I would go up yet another hole on the bottom bar and see what the number is.

 

[Fire Ball]

I got some more gussets welded on the brackets today..
I raised the lower bar up another hole.