Guys,

I'm new here and I'd like to share with you my project that I made recently.

I'm a Braziliam Drag Racer and I had spoken with some Drag Stuff friends that I got here, and now I decided to show you all my job that I did...

I hope that my english be understandable and sorry for my mistakes...

Let's go!

I used the 4 Link Calculator Plus by Performance Trends and Solid Works 3D program to project the components.

My car is a Chevrolet Opala 1976, inline six, 250 CID, 440 HP with 3 Weber Carburetors using metanol and stock clutch. The car weight is 2.700 lbs, and the weight distribution is 51,5% on the front and 48,5% on the rear.

My drag race category is based on the Stock Car, we need to keep a lot of stock features...one of this stock features is the tire. My tire is Goodyear 205/65 - R15, radial and it has 24" of diameter (front and rear).

The ET record of this category is 11,771 sec and my best ET is 12,220 sec. Before my 4 Link System, my 60 feet was 2,2...2,3. Using my 4 Link System the time fell down to 1,969 sec!!


You can watch the movie that I did on the last race:

http://www.youtube.com/watch?v=DvlrOsAW61Y

For the next race I'm thinking to assembly the system as is showed on the picture below. As you can see I let the upper bars with more angle (13,36°) and the lower bars got parallel to the ground. I don't know what's the influence of the lower bars height...I let it near to the axle instead of the last time...near to the ground.

Who can compare for me this differences and its possible influences??? What I'm doing wrong and what can I improve??
Now, I'm purchasing AFCO drag shocks and I'll be measuring several types of rear springs to test.

Thanks for your attention!!!
Best Regards!

Following below more pictures for you comment...

Jeff, click on this link and read the article written by Patrick Budd. He's an extremely sharp guy. It might give you some insight as to what "influences" moving the postions of the 4-link bars might have on your car -

http://www.dragstuff.com/techarticles/P ... uning.html

Thanks Mike!!!!

I already read this article...it has very good tips!!

Maybe you can tell me some experience that you had about it...

...and if my job is ok...or if I have to improve something...

Jefferson, I'm a bit surprised the rules allow you to install a fabricated 4-link system in your car while requiring you to run treaded street tires. For you to drop your 60' times with the suspension change alone must mean you did something correct. Obviously, having to use that tire is the factor you will have to figure out for even more gains. My personal opinion is I would not look into the geometry of the rear suspension any further until you analyze the basic physics of how to make those tires work even better for you. Not knowing your rules, I can relate the things some of the racers I knew who also were required to use treaded street tires tried to imrove on. One trick they used was using a tire "softener" formula like Formula V. They also looked at improving their front/rear weight percentages by moving as much weight as they could to the rear while staying as close to the required minimum weight as they could. Some even went quicker even though their cars wound up being heavier due to the increased added weight in the rear of the car. The better shocks could be a definite improvement as the Competition Engineering shocks aren't really famous for their quality. Try to work on improving the car's "pitch rotation" or as some call it, weight transfer. After watching your video, it doesn't seem the car has any desirable tendancy to lift the front end which would increase the weight percentage over the rear tires and provide more traction. Describe more of what you've done to improve the basic things like weight transfer on launch and the tires you have to choose from. Also, describe more of the rules you are having to follow. Maybe we can find some "loopholes" for improvements. Looks like you're having a blast so, congratulations are in order.

The chassis twisting...shown in the picture in your first post...indicates that you're not loading the rear tires equally on launch. If the fronts don't lift evenly, that can only mean the rears are also loaded unequally. And, with those tire rules, you must have every bit of performance those tires can deliver.I would suggest that you adjust your left side and right side asymmetrically. In other words go for more antisquat on the right side than on the left, with the average at about 100 percent.

Page 19 of my site has a spreadsheet to help in your adjustment.

May I ask what runner length you're running with the Webbers? I'm referring to the distance from the inlet to the intake valve head.
http://www.racetec.cc/shope

Thanks Billy!
That picture was taken during a wrong burn out!! I guess you can consider this picture below...it was taken at the exact launch moment.
I was looking your page 19 on the website...are the bars adjustments always different between left and right side???
I read an article that said you must adjust the 4 link bars with the average at about 85% for cars with original clutches. What do you think about?? I adjusted my suspension around this value...
Did you watch my movie?? What do you can evaluate about it??
I have some movies with the lateral view...if you may send me your email...I'll send it for you!!!
Now I don't know the distance of the inlet to the intake vale head...but you can see below my engine picture...It's a common Weber 44 IDF intake...and the distance is not too long...it would be better if it was a Weber DCOE intake...

Thank you for your feed back!!!

Regards!!
PS: I'll send you a particular message about your 19th website page...I got some doubts...

Since the driveshaft torque is always tending to unload the right rear, it would follow that the right and left side adjustments much be different if the rear tires are to remain equally loaded. This isn't the only way to do it, of course. But, with a competition 4link, this is the easiest way to maintain equal rear tire loading.

Some racers go to great pains to equalize rear tire loading with the car on the wheel scales. But, as soon as driveshaft torque is applied, all that work goes out the window. (Pardon the United States idiom. All that work is wasted.) The wheel scales can still be used, as part of the traction dyno setup, to verify that equal rear tire loading exists during the launch.

At 85 percent, the car is going to squat, which means rear tire loading will oscillate until the shocks get everything back under control. Oscillatory loading is never desirable in a traction situation. For instance, you certainly don't want wheel hop during braking. I would aim for 100 percent antisquat.

Appreciate your offer, but I'm not very good at interpreting videos.

Yes, I, too, prefer the sidedraughts.

From what we learned at Chrysler, the runner length, in inches, should be roughly equal to 84000 divided by the tuned engine speed. Maximum effect is achieved when the tuned speed is in the middle of the rpm range seen in each gear during full throttle acceleration. Judging from the picture, you probably need a bit more length.
http://www.racetec.cc/shope

Mike, I agree with you!!!
Really it's a contradictory question...we are fighting against it...but unfortunately, rules are rules...and maybe it be a good opportunity to show them our job and our 4 Link improvements...


Our rule said: "You only must use nacional tires."
It's so idiot, isn't it?? hahahhahaha


It's a very good case Mike!!! It's so easy to test!!! I'll try it!!! My next race will be August, 15th. I know my engine is very good on the track...so I guess if I increase a little bit the rear weight...I could decrease my 60 feet time...Go ahead!!!


I got a Competition Engineering rear shock broken!!! I can't find the exact adjust because the system broken at the first adjust...and I did exactly as the manual said...
Dave is helping me to buy AFCO shocks!!!


Man, did you hear that the engine fell down when the car held the ground??? I ran 1,969sec eventhough the engine was failing down!!! Look that again!!
I'm wanting to assembly my 4,27 rear end. Now I'm using 4,10 ratio.What do you think??

I have more movies that I could send you...give me your email...I'll send you it and we'll discuss more!!!


I was looking the topic "Spring Rate" and I saw that I did a big mistake!!! I'm using hard springs on the rear!!!!! Because that, I took several rear springs to measure on the equipment to know the exactly spring rate and after, choose the right spring! I read there the Dave's comment...and he opened my mind completely!!! Now I'm running with this issue!!!

Sorry for my long email e thank you your attention!

Actually, it's a pretty cool rule. Makes the competition more about the tuner and less about the guy who has the most horsepower. Work with your tire pressures. Obviously you can't run pressures low like true drag slicks that have soft sidewalls. Look at the tire pattern after a burnout or launch for maximum footprint.
Dave Morgan? Good guy that Dave Morgan. He'll help you as much as anyone. You can also call Afco shock rep Eric Saffell at 1-800-632-2320 ext 202 and tell him I sent you

Most people may not think this is a good move due to the increased torque multiplication but, my previous experience being around the class that was required to run treaded street tires showed differently. The higher number gear ratio slowed down the tire rotation and allowed the tire to hook better and also recovered quicker if the tire spun. So, if I were you, I would make this swap. Let us know the results.



Sounds like you're learning. Dave's opinion on spring rate could help you quite a bit to drive those tires into the track harder. Just good ol' basic physics.

Of course Mike, I'll be telling you all my experiences and results!!!
Since now, You'll need to have patience with me because I'll be ordering your help...hahahahha

Thank you!!

[/quote]

Bill,

About it, look the pictures below. I did different setups for the 4Link bar sides.
What did you think??

These old eyes can't see the difference.
Sorry.
http://www.racetec.cc/shope

hahahahaha

Bill, I changed the setup bars!
I let the right side with 85% of Anti Squat and 100% on the left side as you said about it!!!
Do you think this setup will be good as starting point to test the performance??
Try to save this pictures and open later. The picture will get bigger.

This is exactly the opposite of what you need. The greater antisquat should be on the RIGHT side.
http://www.racetec.cc/shope