Moparts

4 link setup

Posted By: weedlayer

4 link setup - 10/26/14 04:25 PM

I have a 4 link program and have some maps of my setup.

initial setting

latest setting

pick a crosshair

The change, changed nothing. 60' was still 1.50. Had a best 1.405 with Caltracs, should be 1.42 no problem now. Trying to sneak up on it, but at least need to see some improvement. Running new best mph of 129.34, but rest of slip is not in line.

Posted By: Quicktree

Re: 4 link setup - 10/26/14 05:27 PM

what kind of shocks are you running?

Posted By: TRENDZ

Re: 4 link setup - 10/26/14 05:47 PM

So much more info is needed. How did the car react? Did it blow the tires off at the hit? Did it drive out and then spin? Did you try altering launch rpm? Stick or auto? ETC...

Posted By: weedlayer

Re: 4 link setup - 10/26/14 05:49 PM

I new that would be coming

QAL on the front, set at minus as far as they'll go. I assume that would be as loose as I can get the front end. Unless I was supposed to go plus.

CE on the rear set at 60/40 if I set the clicks correctly.

Posted By: Quicktree

Re: 4 link setup - 10/26/14 06:04 PM

need to get a video and actually see whats going on before you go making a bunch of changes on the 4 link.

Posted By: weedlayer

Re: 4 link setup - 10/26/14 06:24 PM

It's not blowing them off or unloading. I do think it is developing too much wheel speed.

So far, been twice, just me, so no video.

I do know, mph is up about 3, et overall is down, but 60 is not improved or even a little worse from before the changes.

There are more adjustments that still keep me within the program recommended area. Just don't know how radical to get
with their settings.

I want to keep the front wheels at least somewhat close to the ground.

I have dropped the tire pressure from 15 to 12, and that has changed nothing. Tires are 13.5 x 31 with tubes.

Posted By: Quicktree

Re: 4 link setup - 10/26/14 06:27 PM

how old are the slicks, did you ever scale the car?

Posted By: weedlayer

Re: 4 link setup - 10/26/14 06:30 PM

slicks are new. 1710# front, 1520# rear.

dropped over 200# from last configuration. enough to gain 3 mph

Posted By: Quicktree

Re: 4 link setup - 10/26/14 06:32 PM

it will take some time to get it sorted out. set the 4 link up neutral with no preload and don't go making a bunch of changes at one time.

Posted By: FastmOp

Re: 4 link setup - 10/26/14 06:36 PM

Bottom bar should be slightly lower in the front. Not running uphill like yours.

Posted By: Quicktree

Re: 4 link setup - 10/26/14 06:42 PM

Quote:

Bottom bar should be slightly lower in the front. Not running uphill like yours.

good catch, level or slight down is where mine end up.

Posted By: CMcAllister

Re: 4 link setup - 10/26/14 08:38 PM

130MPH. 3200#. 53% on the nose. 2.45 low?

Looking at the diagrams, looks like the 4 link chassis brackets are too high in the car. Don't know if the bars can be put where they need to be. Looks like the first configuration is closest, but there's no room for improvement. Top bar should be as far from the housing as possible and running maybe 15 degrees down (at least). Bottom bar also as far from the housing as possible to start. Maybe downhill a degree. If it still doesn't hit the tire, try making it level or up in the front slightly to help apply the tire. Bottom bar rarely needs to go beyond a degree or 2 up or down. Start the rear shock dead loose on extension. Keep the compression in the middle. If it's not a double adjustable, just get the extension as loose as you can. Instant center should end up 40-42" out. Start there.

Yes that's short. I've run them shorter with that power level. Converter design, gear ratios, stick vs. auto, stroke, and a hundred other things influence it. Lack of horsepower/weight distribution = you have to get aggressive with it.

Posted By: weedlayer

Re: 4 link setup - 10/27/14 02:23 AM

ok, starting to make sense. I can lower the bottom shock mount a hole or 2 and lower the body, that would drop the front bar holes giving more down or straight angle options for the bottom bar. Sits kinda high in the rear anyhow.

Shocks are only 3 way adjustable.

Quote:

Our Rear Drag Shocks are also adjustable in three ratios: 70/30, 60/40 and 50/50. These ratios also represent the percentage of force required to compress and extend the shock unit. Only this time, the first number is compression and the second extension.

excuse my ignorance, but which is loosest on extension?

also, now that I know what weight is actual, what coil should I have on the rear for 1520#?

Posted By: Quicktree

Re: 4 link setup - 10/27/14 02:32 AM

a good set of double adjustable shocks would be a good investment.

Posted By: JD Dart

Re: 4 link setup - 10/27/14 05:28 AM

If it was me I would put it in the top axle bracket top hole because you don't have a ton HP you need the mechanical advantage.
1. Top Axle bracket top hole.
2. Bottom Axle bracket bottom hole To get more spread on the bars this may not work for you again you need more HP mostly more spread is to calm done tire shake.
3. Top chassis bracket 3 hole down from the top.
4. Bottom chassis bracket bottom hole.

Try for IC 47'-53' and 7'-4' up But I don't

Posted By: 68roadrunner

Re: 4 link setup - 10/27/14 03:07 PM

#130 springs on the rear

Posted By: Al_Alguire

Re: 4 link setup - 10/27/14 08:06 PM

Jess's advice is pretty good. Shocks need to be good, spring rates, well opinions vary. Me I like just enough to hold the car up. Get some scales or get it scaled as well.

Posted By: CMcAllister

Re: 4 link setup - 10/28/14 02:41 AM

130# springs is what I would start with. You'll have to compress them them to get the shock to the right installed length. That will store some energy and help get the tire applied. Without a decent double adjustable shock, you may as well have put ladder bars on it. Proper installed length of the shock has to be maintained after moving ride heights and shock mounts. Lowering the car some would help the 4 link geometry. Ideally, with the rear at ride height, the bottom hole in the chassis bracket should be the same height from the ground or slightly lower than the bottom hole of the axle bracket.