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KY , my 4-link has an IC of 47.45" & IC Height is 5.38". The wheelbase is 108". I also have a 1/2 flat of positive preload. What else would you like to know? :D

Rick, I am glad you found that so funny..... :lol:
 

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Discussion Starter #4
Thanks Chris. I was just wanting to compare to mine. I am getting ready to change it. Mine is 110 " wheel base . The ic is 40" out and 5.5 high. It seems like it is slipping a bit after it leaves by watching the video. Maybe I need to put a 16 volt in the trunk for ballast :lol: Just jerking at ya 8)

Do you know how many degrees down your bottom bars are mine are 4* down in the front.
 
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Randy, I am sending you an e-mail with a picture of my 4 link set up. It will help when I explain something on my 4 link. :D
 

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The I/C differences of 47.45" and 40" are interesting. You could also compare slick size/stiffness/compound, race weight, the height of the engine crank snout C/L off the ground, & shock/strut valve settings.

The 4-link software that's out there can be useful for plotting where your I/C is, but it might not predict exactly how cars from different builders (using the same I/C settings) will compare. The differences in 4-link bracket designs from the different manufactures (and the differences in the amount of instant center change during the launch) makes it harder to really compare cars from different manufactures.

It's interesting to compare the pro chassis brackets from different builders. The Vanshing Point chassis bracket height looks close to being equally divided between the top bar/bottom bar holes. Compare that to the Rick Jones and Tim McAmis brackets that both have a larger percentage of the bracket's height devoted to the top bar's holes. The layout of the bracket's hole arc radius looks to be slightly different between the assorted shops too.
 

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Discussion Starter #8
Dilligas , in my opinion my car is not transferring enough weight. I have had 1.22-1.25 60' times and have yet to pull a front tire off the ground. On video it looks like it hooks and then spins. It is not squatting the suspension or separating it looks like it just hits the tires softly and then unloads. If I move my top bar up 1 hole it will change the ic from 5 1/2 @ 40 to 5 1/8 @ 48 the way I plotted it out. I ran the #'s through a computer program , but they vary a bit from my manual layout. They vary about 2" on length and about .100 on height. Do you think that would be a move in the right direction ?
 

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I haven't seen all of the videos yet, who's clip had the best shot of your car launching? I think you said your running around 5.50's - 5.60's in the 1/8 mile. Is that without a power adder?

There are so many different factors that work with/against the 4-link settings & can govern how well a given car works in the first 60ft. How much usable power/torque you have at launch RPM, engine set back & height off the ground, shock/strut settings, gear ratio, tire size, etc,etc, etc.

Before you think about making a 4-link change, you might look at a few other things first. Are the slicks fresh? Is the converter OK or going away? Is the rear shock extension valving so loose that the suspension's initial "hit" is too violent and unloads the slicks? Is the rear shock compression valving too tight, causing the suspension to unload when the car gets on the wheelie bars? Are the shocks bottomed/topped out because of springs that are too stiff/weak? Are the front strut's extension valving set too tight & not allowing enough weight transfer to work with your engine's power range to help keep the slicks loaded?

If after some more track testing the car works better with the rear shock's extension valving ending up adjusted to "full tight", (and the car is still on the violent side), you might think about moving the I/C out and/or down some. If it works better with the extension valving adjusted looser than half way (and the initial hit is still real lazy), you might try moving the I/C back and/or up some.

There are a bunch of smart people on this site that will hopefully chime in as well, there is always more than one way to get an adjustable car to hook. More opinions/info is more gooder!
 
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