TCI 4-link for 62-67 Nova ?'s - Lateral-g Forums

slow4dr · #1 04-25-2006, 12:20 PM

I am sure most of you are familiar with the TCI 4-lin for the early Nova. If not here is a link. http://www.totalcostinvolved.com/pro...cfm?ProdID=227

I am building a drag car that will double duty as a street/touring car on the off weekends. I have contemplated many different things but I keep coming back to the TCI kit. I was mainly going to buy the frame rails, drive shaft loop, tranny cross member, sway bar, axle brackets & frame mount(basically everything that is red in the picture above + sway bar). I am thinking of making my own bar links out of chromoly, adding some nice Heim joints and then get some nice adjustable coil-overs. This is where I keep getting a brain fart.

I hear all to often that 4-links aren't very pleasurable on the street(especially hard mounted with heim's). What I have been contemplating is using the TCI platform and making my own 3-link with their existing hardware. I don't mind cutting up the floor a bit to mount a center link but I do not want to remove the rear frame rails. There are many reasons for this that I don't want to get into here but they are NOT going to be removed/altered.

Here are my priorities. straight line > street civility > lateral

What do you guys think, 3-link or 4-link?

Mean 69 · #2 04-25-2006, 04:34 PM

3-Link. Period.

M

rocketman · #3 04-25-2006, 05:02 PM

three links dont make for a good drag race set-up.unless using a tq arm.
the tci stuff is great,i have built alot of street rods with there stuff,never a problem.

a 4 link style set-up with poly or delyum bushed hiems is not bad.very nice ride,quite.i wouldn't worry about.

3 links are only a must have for autocrossing.i dont like solid bar 3 links
tq arm style is very nice like a bmr tq arm,i am going to use one on my new street rod project.

Mean 69 · #4 04-26-2006, 08:27 AM

Can you specifically explain why a three link is not good for drag racing? We are all entitled to our opinions, but I could not disagree more with this statement.

A four link system using rod ends or delalum type bushings will bind terribly in roll, physics just won't allow the thing to work around turns. The only reason that drag style cars roll around turns at all with a four link is that something, or many things, are flexing. Could be the frame, could be the links, the rear end brackets, you name it, but it is physically impossible to roll a four link with solid type end links without mechanical bind. Sorry. Poly will be better in that it can compress, and will allow more roll until it can't compress any more, but poly is also stiff, so it'll resist roll too. Rubber is the best, and actually, only solution for the street for a four link.

A torque arm setup is not a three link, it's a torque arm. They can be made to work pretty good, but there are a few really critical tricks for making them work well, and the geometry is usually tough to find a really good overall compromise. If you go too short with the t/a, you have to worry about rear brake hop, too long and you really need to be concerned with the strength of the t/a because it carries basically all of the axle torque. Nothing is free, unfortunately.

M

slow4dr · #5 04-26-2006, 09:36 AM

Thanks for the input guys.

On a 3-link should the upper link be shorter than the lower? Is there a percentage of difference they should be? In the pic linked above could I attach the upper link to the top of the drive shaft loop and the lower links to the cross bar essentially making them all the same length.

I am also just learning/reading about the "watts" link. The 4-link above comes with a PHB so I am thinking I should just delete it and run a watts instead. It appears that the rear frame mount on the TCI kit would be in an almost perfect position given a tube was added to drop the mounting point lower.

Mean 69 · #6 04-26-2006, 09:52 AM

Hey Jason,

Like everything, there is no "right" answer, it all depends upon what you are looking to get out of the car. As for the length of the links, longer is better in the general case, the suspension will handle transitions more smoothly (things like the instant center, virtual swing arm length, etc transition nicely relative to a setup with short arms). The ratio of the upper to lower will mostly manifest itself in pinion angle changes, and here again, there is no "right" answer, but I can offer this observation. Usually, the folks that supply three links are trying to fit everything beneath the factory sheet metal, and as a result, the upper link tends to be really short, like the new Mustang's. This is FAR from optimal, and not only do you get pretty dramatic pinion angle changes, but the rest of the important suspension characteristics change really rapidly when the suspension compresses, droops, or rolls. The result is instability, which can sometimes be tuned out with shocks and springs, but usually not, and certainly not for a car that will see a variety of road conditions. Honestly, this is a case where "size matters," and anyone telling you differently is trying to sell you a packaging compromised setup. It is a really easy thing to show on paper, and a really easy thing to show in reality too.

A decent place to start is to make the upper link about 70% or so of the lower link length, and I stress, this is a "START," not the end-all answer.

A really long Panhard Bar is a great setup, they can work very well when executed properly. In our setups, we use the Watt's, with the bellcrank mounted on the frame. This solves two issues, one, it eliminates lateral axle motion in bump/droop/roll that is present with the PHB, and two, it fixes the "roll moment" of the suspension system, so the springs and sway bar see a constant roll force, independent of the position of the suspension bump, etc. It's more complex, but in our opinion, it's worth every last cent.

Best of luck with the project, sounds like a bunch of fun!
Mark

rocketman · #7 04-26-2006, 09:41 AM

a 3 link drag racing,buts the load force on top housing,and can push the center down lifting the tires,basiclly making a u shape out of the rear end and un load the tires.
as where a 4 link loads both axle tubes,delivering an even load.

i never said a 4 link is going to corner that great.if you know what a 4th gen camaro rear suspension is like it a 3 link style with a tq arm bolting to the center section,this makes a very good set up for both.

4 link race car chassis do flex to turn,they just dont make sharp turners,i drive a pro street car with a 4 link,solid hiems,and it is totally drivable,it wont take a road course.

there's no way to have a drag style car that will corner like a road race car and be fast on the strip,which is what he said he was wanting.