74_5.0L_Z

I was poking fun at the picture. I was not criticizing. I'm quite sure that my situation looked just as comical to innocent bystanders.

I'm sorry, but that looks like it should be included as a workplace safety message. I sure my job would have been included on the same page.

After I finished the tube front end on mine, I needed to prep and paint the bottom of the car (from the rear crossmember forward). The front suspension was removed and there was no drivetrain or interior. The rear suspension was installed, so I grabbed the two front frame rails and rolled the car out of the garage like a big wheel barrow. Once in the driveway, I blocked the rear tires and stood the car up until the rear valance was almost on the ground. I secured it in this position with a rope up to a tree limb above. I was then easily able to scrape, clean and paint the underside of the car.

I switched to Hypercoil springs because I have heard that they have less variation in spring rate than some of the others. But yes, if I ever get truly serious, I would need to measure the rate and free length of every spring (and recheck periodically). In the meantime, I'll get as close as I can using off the shelf spring rates and movement of weight. The deeper you look, the deeper it gets.

I will try to measure the bar. A simple experiment is worth a thousand calculations as long as all the variable are covered. How long are your lever arms on your sway bar? Were your bearings located near the stock location near the bend in the bar? How flexible is the workbench that it was bolted to? Were you measuring the deflection at a point equal to the end of the lever arm, or were you measuring the deflection at the end of a longer lever?

I dug out my statics text and went through the torsion calculations and if I assume infinitely stiff lever arms, I get pretty close to what the WTW calculates for a 1" sway bar. The WTW comes up with 659 lb/ in (That's one inch on each side), and I came up with 592 lb/in (Again one inch on each side). I do plan to measure the rate, but I am pretty darn sure that it will measure greater than 120 lb/in. Is it possible that you annealed your bar by welding on it? I have seen suggestions that sway bars that have been welded need to be heat treated.

I already had my 1" sway bar in place and haven't had time to measure it's rate or install the sway bar that my calculations say should work (stock 0.71" sway bay modified for rod ends and 7.5" lever arms). I ran the car with the 450 lb/in rear and 425 lb/in front with the 1" sway bar. The weight transfer worksheet gave me a magic number of 9.4% which predicts understeer (which it did). With the new sway bar and swapping the springs front to rear, the weight transfer worksheet gives me a magic number of 3.2% which is much closer to neutral. My calculations for the sway bar rate agree pretty closely with what the weight transfer worksheet predicts. John, I plan not to miss any more seat time regardless of the springs that I have installed. My next event is one month from now. By then, I will have the new sway bar set-up in place and hopefully the new springs. I'll wait till I get the new springs in place before I get it balanced. Oh, my weights are with me in the car and a full load of fuel.

I ran an autocross yesterday with my new set-up (sort of). I had all of the new springs and struts in place, but I haven't had the opportunity to re-corner balance the car or get it aligned. Additionally, my front sway bar is much too large for the springs that I have chosen (I was pushing a bit). Nevertheless, the car did pretty well. I took first in E-mod against 4 other cars in my class. I will say that the new set-up will take some getting used to. The car reacts much quicker with a 2.5 Hz suspension frequency than with a 1.8 Hz frequency. I think that I will like it as I get accustomed. As I was inspecting the car today, however, a strange and troubling thought occurred to me: These cars are not symmetric left to right. The left side is heavier than the right side. Yet, the spring that I put in the left front is the same rate as the spring that I put in the right front. The left front sprung weight is 586.6 lbs and the right front sprung weight is 543.6 lbs. The resulting frequencies for the left front and right front are 2.28 and 2.37 respectively. The resulting frequencies for the left rear and right rear are 2.20 and 2.28 respectively. So, what does all this mean? It means that in order to have the suspension frequencies match left to right, the car needs four different rate springs. For mine, I would use the existing 450 lb/in spring on the left front, and use a 410 lb/in right front spring. On the rear, I would use the 425 lb/in spring on the left and need a 390 lb/in spring on the right rear. By doing all of this, the car should sit level when corner balanced and transfer weight forward and backward equally between the left and right tires during acceleration/braking. Please someone tell me that I am full of crap. Otherwise, I will be ordering two more springs.

One other possibility has occurred to me. If your timing is retarded (at idle) so that you get spark at a few degree after TDC instead of ~12 before TDC, you will get a situation like you've been describing. My father in-law's 1964 comet was having similar issues to those you are having with yours, and setting the timing correctly cured it.

An easy way to test for a bad or mis-installed thermostat is to remove it. Run the car with the water neck reinstalled (sans thermostat) and see if the problem goes away.

I think you have the thermostat in upside down.

Congratulations John. I look forward to checking out your car in the magazine.

Name: Dan McGrath Handle: 74_5.0L_Z City/State: Rockledge, FL Year/Model: 1974 260Z Vehicle Details (max 20 words): 5.0L Ford/T5, Tube chassis, custom GT-40 style hood and air dam Vehicle Picture:

I worked through Cary's spreadsheet and also though all of the calculations in chapter 16 of RCVD and worked out my new spring rates to go with the new struts. I ordered my new springs yesterday. In the rear, I plan to run 8" 450 lb/in springs and no sway bar. In the front, I plan to run 8" 425 lb/in springs and a 7/8" sway bar. This set-up combined with the weight distrubution, roll centers, unsprung weight, motion ratios, and such should result in a front load transfer that is about 5% higher than my front weight distribution. My resulting undamped natural frequencies will be 2.39 Hz for the front suspension and 2.44 Hz for the rear. Looking at the koni 8610 graphs, the 8610-1149 shocks will work well with these spring rates in the mid range of their adjustment, and the 8610-1437race struts will work well with these spring rates on the low end of their range of adjustment. I am working on the assumption that a damping ratio of ~0.7 is desirable in the 0 to 4 in/sec range of damper shaft velocity. In addition, I discovered an interesting thing while comparing the 8610-1437 to the 8610-1149: The 1437 has a longer stroke than the 1149, but the 1149 has a longer overall extended length. I discovered this because I was trying to regain some droop travel in the rear. By moving the 1437 from the rear to the front and the 1149 to the rear, I was able to regain 3/4" of droop travel in the rear. Moral of the story: I would only section the rear struts by 1.5" if you are using the 8610-1437race strut. The strut housing can be sectioned more for the 1149 insert.

Add me to the list of people that got smacked up side of the head by their drill while cutting notches. Also be aware that the metal around the newly completed notch will be razor sharp and very hot. I'm sure no one needs to tell you to wear eye protection.

I haven't forgotten you. In fact you got me thinking (damn you). My current sway bar is a 1" attached to the lower control arm at approximately the stock location. The installation ratio at the stock point will be pretty low because it is well inboard of the ball joint. But, if you flip the rod end over and attach it to the strut, the motion ration will be pretty close to the strut installation ratio. What this means is that I will be able to use a much thinner (lighter) sway bar and still get the same amount of roll resistance. That is one of the things that I am still working on. I'll post the results.

Another busy weekend: I did the following: 1. Determined my roll centers. 2. Re-measured the motion ratios 3. Played around with Smithee's Weight Transfer Worksheet using the data that I know about my car. First, I'll detail the procedure that I used to determine my roll centers. The process required measuring the following: - Front and rear track (center to center) -lengths of front and rear control arms (center to center) ---14.5" rear and 11.25" front. -spacing between the left and right LCA pivot points -height of front and rear LCA pivot points from ground. -spacing between left and right pivots for the tops of the struts (center of spherical bearing). -heights of front and rear strut top pivot points above ground. I performed the whole process twice on the front suspension (once with no bump steer spacer and once with a 1" spacer). My results were that my rear roll center is 3" above ground and my front roll center is 2 " below ground (with no spacer). The front roll center rises to ground level (0.014") when I installed the 1" spacer. Here are screen shots showing the excel graph of the front and rear data: I reperformed the motion ratio measurement (just to be sure). This time I did the front at the hub center like last time and I also redid it at the tire centerline. The hub centerline and tire centerline data agreed with each other, but both were slightly different than last time (I think I was a little more careful this time). Additionally, I decided to install the bump steer spacer and see if there was any change in the motion ratio. The results from all of this is as follows: Front: --Hub center and tire patch center (no spacer) Installation ratio = 0.915 --Hub center with 1" bump steer spacer installed Installation ratio = 0.8911. Rear: --Hub center installation ratio = 0.901 What can probably be discerned from the variation in my results is that the error in my measurements doesn't justify my reporting more than two significant figures. So we'll just say that the rear motion ratio is 0.90 and the front motion ratio is 0.91. So, where does this information get me? Hopefully, it gets me closer to picking some new spring rates. Toward that end I plugged all of my data into Smithee's Weight Transfer Worksheet and found some possible spring combinations. I'll write up the details of that later, but I believe that I am going to end up with 350 lb/in rear springs and 375 lb/in front.

I've posted completed pictures of the car elsewhere, but for closure of this thread I'll post them here too. The first three were taken at the National Z car convention in Daytona. The next were taken at an Autocross two weeks ago.

Here is what I used: http://www.pro-tools.com/hsn500.htm Great tool. I cut literally hundreds of notches. As stated earlier: Use a good bi-metal hole saw. Go slow Use plenty of cutting fluid.

Where am I going with all of this? I'm working through chapter 16 of Race Car Vehicle dynamics because I'm an engineering geek, and because I want to have a better understanding of how my existing suspension works before I change it. Chapter 16 deals with ride and roll rates and requires that you have knowledge of the following before you can do any meaningful calculations: Corner weights (been there done that) http://forums.hybridz.org/showthread.php?t=92703&highlight=corner+weights Unsprung weight (check) Motion ratios (check) http://forums.hybridz.org/showthread.php?t=129623&highlight=motion+ratios Front and rear Roll center heights (That's next) Center of gravity height (I would like to do this but I may have to estimate) Tire Spring rate (This would be nice, but I'm not holding my breathe). Does anyone have a good ballpark figure? In parallel I plan to work through some of the Chapter 6 stability analysis. As I said, "I'm a geek".

The weight of the Group B items is divided by two because one end is fixed to the sprung mass, and the other is moving with the unsprung mass. The approximation of 1/2 applied for the Group B items (control arms, half shafts, tie rod) assumes symmetry and introduces a small error for items whose mass is not evenly distributed. Fortunately,(or unfortunately) the weights all of the Group B items are small compared to the Group A items. All of the Group A items are 100% unsprung, and no approximation was necessary. The error from approximation of the Group B items is very small compared to the overall unsprung mass.

I was pretty surprized as well. As you can see, the wheel/tire and the brake rotors are the heavy hitters.

Today, I spent the entire day in the garage weighing and measuring suspension components. This is all in an effort to quantify my unspung weight and also to get a good handle on my instant centers. I'll publish my results for the unspung weight here: Front: Group A: Strut housing with hub, lug nuts, and brake disc_________31.0 lbs Ball joint and steering arm ___________________________2.6 lbs Wheel and tire (Hoosier A3S04 245/45/16)______________39.6 lbs Caliper and pads (Outlaw 2800 caliper w/Hawk 237 HP+) __4.5 lbs Group B: Lower Control Arm __________________________________2.4 lbs T/C Rod Assembly __________________________________2.8 lbs Strut Insert (Koni 8610-1149) ________________________4.3 lbs Tie rod ___________________________________________1.4 lbs Spring (Eibach 10" x 2.5" x 200 lb) ____________________2.9 lbs To get the total front unsprung weight for one corner you sum the items in Group A and add half of the sum of the items in Group B. The total for the front is 82.5 lbs. Rear: Group A: Strut Housing with brake rotor, stub axle, spindle pin, CV adapter,caliper adapter, and lug nuts.__________________________________________________42 lbs wheel and tire (Hoosier A3S04 245/45/16) ___________________39.6 lbs Caliper and pads (Outlaw 2800 caliper w/Hawk 237 HP+) ________4.5 lbs Group B: Strut insert (Koni 8610-1437race) __________________________4 lbs Rear Half Shaft (300 ZX turbo) ____________________________14.7 lbs Rear Control arm (Custom tubular) _________________________ 7.5 lbs Spring (Eibach 10" x 2.5" x 250 lb) __________________________3.1 lbs To get the total rear unsprung weight for one corner you sum the items in Group A and add half of the sum of the items in Group B. The total for the rear is 100.75 lbs.