My dad used to race a '72 pinto in compact modified. They would constantly chase the wheelie bar setting because the short wheel base on the car made it really picky. They were running a 4 link too. They set up the bars softer one day because the weather said the track was going to be a little slick. Well on the launch all dad can see is the sky. When he grabs second the front end came up on him pretty good again. Needless to say he and my uncle had some words when he got back to the pits. This was all with the 2.0L SOHC and I think they had the 5 speed in there by then with the Dana rear.
I'm gonna give it a go Friday night..raising them a little at a time until I get to a point of diminishing return...get some video of the bars and tires at launch...I could easily raise the front of the car transferring the center of gravity to the rear. Right now the car is equally weighted on all four tires, 567 lbs.each.. I'll just play with it and see if anything helps...if nothing works I'll put it back like it was and punt...I reckon thats why they call it Test & Tune. Simon I'll post a pic of the throttle rod setup...that will answer any questions. Todd if you can offer any other ideas on things to try I'm all ears
Only thing I can offer at this point is that you can't change the center of gravity. But, you can transfer the weight more towards the rear by playing with 4 link settings. In laymen's terms, you can think of it this way. Think of pushing a refrigerator across the floor in your kitchen. Now, the point where you put your hands to push is the instant center location. If you push up high, you are not moving the fridge across the floor very much if at all...only pushing the top forward, and eventually it'll fall over. If you push at the bottom, you are pushing the bottom out from under it so to speak. It takes quite a bit more effort to move it. Now, somewhere in the middle is the "sweet spot"...takes very little effort to get it to move across the floor, and it is moving in such a way that it is neither top heavy nor extremely hard to push. rear suspensions are the same way. Your car is different than ANY other car out there, which means just asking what would work best is a crap shoot. TRYING it is the only way you'll know. Even if you had 2 identical Bickel pro stock chassis...they are totally different. What works for one can be disaster for the other. That said, the corner weights are pretty darn good! Especially for a door car. I've never run across a door car that had a perfect 50/50 distribution like that...never even heard of it to be honest. Changing the IC location won't make your static corner weights any different, but when you launch, you'll notice a big difference. After you plot out the 4 link (easy...as mentioned earlier) you can decide what holes the bars go in, then set the preload (if you use any) to get your corner weights back. Then go racin'. Plotting the 4 link is easy. You have a good shop floor, right? Well...what you're going to want to do is get a piece of notebook paper, draw out a picture of your 4 link...jsut the brackets and holes will work. Measure each hole location from the floor with your car sitting at ride height and the driver's weight in the seat. I used 3 crankshafts, a cinder block, and an old 460 head to simulate my weight. Some folks may have to add a few extra heads or cranks...but I'm tall/skinny and feather-light (around 170 lbs). AFter you have EVERY hole measured out and logged on your notebook paper, you can "name" the holes. I like to make the front holes the letter holes (a,b,c,d,e,f, etc) and the rear holes numbers. Now, get some chalk and start drawing a full-size view on your garage floor. The more accurate you can get it, the better...and use as much detail as you can. I like to draw a halfass view of the lower part of the body and the rear axle CL on the floor...as well as an outline of a tire. Then, look at the car again and think about which holes the bars are placed in. go back to the floor and connect the 2 points, and continue the straight chaulk line far forward of the front bracket....then do the same with the bottom bar, connect the dots and extend the line. Where the 2 lines intersect is instant center. It sounds confusing, but it is really VERY simple...once you sit down and think about what youre doing. There are also some 4 link calculators on the web, but I've found that they are much too easy to use...and really take the thought out of plotting it. Doing it the old fashioned way will teach you the importance of how everything works together. Being the person I am (technical oriented) I want to know HOW something works before I know that it does in fact work...and many times it has proven effective in tuning. Again, the door car "bible" will explain all this, and in greater detail. Best of all, there are pictures...for those of us who don't comprehend reading very well (like me). The book isn't cheap, but it is by far the best investment I've made in reguards to chassis tuning. Wanna get really confused? Remember, when the chassis loaded, the rear bars move...and this changes the IC location. Another reason that a 4 link is far superior to a ladder bar. It's entirely possible to have an IC location that is prone to lift the front end upon the initial "hit" but after the hit, IC changes more rearward and downward...and settles the car down. Thats how mine is set up. Shock setting play a big role too.....confused yet?? 347...sometimes it's more fun to just sit back & watch the thread. I get a good laugh from time to time.
