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Mikelly

Suspension....What do you run?

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Suspension setup can make or break a V8Zcar. I remember my very first experience with a V8Zcar turned me against them for a long time. The original Scarab conversions put the weight of the drivetrain directly over top of the steering rack which made the Z handle like a Drunk blond riding a mechanical bull, lots of fun to watch, but not to fun to join.

 

Now days we have the right solution to the V8Zcar conversion, thanks to people like JTR, Johns, and Motorsport. All of those kits move the motor back far enough to allow for proper weight distribution and low enough to keep CG well within acceptance. However, there are a number of things that can still be done to help any z, and especially V8Zs handle that extra torque and HP.

 

Question is though, what do you plan to do with your car? You can set up a Road race type suspension to handle 1/4 mile duties fairly well (As witnessed by C5s, Viper GTS', and Porshe 911 TTs) but it is hard to get a drag specific chassis to go around corners well. So what do you do? If your bag is drag only, the best you can do is get the front suspension loosened up, release the sway bar endlinks (Helped me raise one wheel off the ground with an L6 motor), and run lighter springs up front. That is about the extent of my drag racing suspension experience....Pretty sad huh?

 

On the plus side I can tell you about setting a car up to go right and left. Factory rubber bushings really take a beating over time. These should be your 1st area of attention. Every control arm, end link, frame mount, and diff mount needs to be addressed. Doing endlinks and sway bar frame mounts are faily easy. However, doing lower control arms in the front or rear can be a real problem. Heat or a large press can be a good thing. Torches usually are the best tool to use when burning out old rubber and knocking the old sleeves out. Don't forget your mustacha bar. Solid mounts are not necessarily a good thing for day in, day out driving. Solid mounts in the motor and trans transfer a ton of vibration into the cockpit of the car, and over time can become an annoyance. However, I do recommend the solid Diff mount for the front of the Differential.

 

Sway bars... understeer is a big problem with V8Zcars and added torque and factory settings. I recommend running the rear sway bar (7/8th diameter) and a large 1 1/8 or 1 1/4 diameter sway bar up front. They help with understeer bigtime. Also the bumpsteer mod mentioned in the JTR manual is a good thing to add. Also, I use quick steering knuckles and a hard plastic steering coupler to help with quicker and more precise steering.

 

On to struts and springs. Some people have the misconception that slamming a car on the ground is the way to make your car handle. Unfortunately, most times when you use cut or lowered springs, you loose a substantial amount of suspension travel. 1.5 inches lowering from a spring is about optimum for retaining adequate suspension travel. This is very important for several reasons. You want the car to be able to react to the road conditions, dips, pot holes, bridge joints, without becoming unstable. When I was 22 and just learning about these things I was given a set of Road Race springs for a 240Z. They dropped the car almost 3 inches, which helped lower the CG, but also cut the suspension travel down by 3 inches. I crushed my bump stops so bad that they broke off the strut, which eventually started to leak because the spring really wasn't allowing for proper movement of the strut. The spring rate was either 500# or 800# which was way to stiff. Eventually I got my hands on some Traction Master springs and Boge struts and the car was perfect. Those springs dropped the car by 1.5 inches and that combo, along with the other mods listed above and a cage and sub-frames was the setup I raced in SCCA Pro Solo2. Coil overs are the answer for lowering a car without loosing suspension travel. Some folks don't think they are necessary for the street, but they solve several problems for the Zcar. 1St, they help with clearance of wider & over sized wheels, and 2nd they help with dialing in a suspension setup for each drivers personal taste. Swapping spring rates is much easier with a coil setup and you can adjust rebound on a coil-over setup.

A note about spring types: There are specific rate springs and there are progressive rate springs. Specific rate springs are more of a race application. The spring rate is the same throughout the compression of the spring. A 200# spring is going to begin life at 200# and bottom out at 200# which makes for a harsh ride. This is great on a race track where surface conditions are mostly smooth and predictable. The street isn't so friendly though. I'd opt for a progressive rate spring for a car that was going to see any street time. Progressive rate springs start life at a lower pound rating and and increase stiffness as the spring is compressed. This is ideal for road going cars, because you can get a comfortable ride yet have the compliance when you throw it into a corner or offramp. Progressive rate springs have three areas: a begining rate, usually very compliant, a transition from the compliant rate to the firm rate, and the last third of the travel which is stiffest for aggresive driving. Typically you will have a spring rate of 125#/200#. This means that the spring rate starts out at a soft 125#, but ramps up to a firm 200#. This is just and example, but that is the basics on the two most common spring types out there!

 

Now Camber and Caster are another issue. Caster is hard to adjust on Zcars because there is no factory adjustment for it. However, the TC rod can be shimmed forward or altered all together with a threaded Heim joint to allow for positive caster. A setting of plus 6 or more degrees (I used to run 8) is desired. Camber, now there is a point to argue...for the street many folks tend to run .50 neg. camber, but I prefer 1 degree front and rear. Too much can be bad, but Zs definitely benefit from negative camber to both wheels. I don't recommend Gmachine camber bushings because they wear out easily. However, after stating that I will admit I have them in the rear of my current ride. I'm looking at fabricating my own rear lowers. Some folks state that Heim joints aren't worthy of road driving. I argue that. I've had the Arizona Z "STYLE" lower control arms up front for quite some time without a problem.

 

Strut braces are nice, and functional. I prefer the units made by motorsport. I also strongly recommend sub-frame connectors and a six point cage to help stiffen the unit body!

 

So what do you guys think???

Mike

 

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"I will not be a spectator in the sport of life!"

mjk

 

[This message has been edited by Mikelly (edited February 17, 2000).]

 

[This message has been edited by Mikelly (edited February 17, 2000).]

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All very good points. I will be using front coil overs with VW Rabbit GTS strut inserts in cut down struts. Probably Ground-Control, and camber/caster plates. In the back I have coil overs on my 12 bolt chevy. I put these in so the tops are closer together than the bottom ( / ). That and the Panhard bar should keep my rear end stable in the curves. I have all polly bushings front and back. I also have a 1 1/8 front sway bar. none in the back yet, I want to see if I need one there.

 

[This message has been edited by Mike kZ (edited February 17, 2000).]

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Mike, What would be the best set up for me?

My engine sits 1/2 inch off the firewall,

but it sits a little high (i had to for

angle plug heads/headers to clear stearing rod). I like street cruizing/racing and some cornering but nothing major. I will run it

a few times in the 1/8-1/4 mile just to see my actual times. I already put in the eurathane steering rack bushings and the

aluminum cup and plastic ball bushing(i cant remember what it is called). I have 16x8 and 205/50 z rated rubber. I know that i need

struts and springs and a strut tower brace.

My hood is almost touching the insides of the fenders, I guess this is from the prolonged weight of the v8 causing the unibody to sag... the car feels topheavy

give me some brands and part numbers and i will order them.. I think i will make the strut tower brace my self though

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I would be seriously addressing the "SAG" issue ASAP Myron. That is a big deal. Sounds like you may have degredation in your framerails, inner fender wells or floorpans. Something isn't right and you need to find out what it is and A: re-align the frame/ Unibody, and B: weld in the fixes.

 

After you address that issue, I'd get a set of Koni "D" series struts From Arizona Zcar if you have a late 74-78 Z and a set of their springs, or Springs from Motorsport. Make sure to get a nice progressive rate spring. I'd get a rear strut brace to go along with the front, and I'd make sure to replace ALL bushings in the control arms, mustach bar, and replace the Diff strap and rubber mount with a solid metal mount. Ths Aluminum cup & Plastic ball assembly you installed goes on the TC rod that bolts to the lower control arm and the unibody up front. It helps aid in strut/wheel assembly deflection, which cause each wheel to change caster, camber and toe under hard cornering, braking or adverse surface changes!

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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As it sits right now the passenger floor pan

is sitting in my garbage can, along with the rusted out frame rail. It appears that the original owner drove the car over some parking bricks or something. the passenger

frame rail was heavily damaged/rusted out. I am pulling the engine and tranny this weekend and will be repainting everything and building some sort of sheet metal heat shield for the wiring harness. I have a chassis shop guy that wants to trade some labor for my dads old 9" lathe. SO hopefully

i will het that done very soon... Now that i got a taste of how fast it really is i am

going nuts to get it back on the road!!

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The Z is made for curves IMO...

I run a coilover set up from Ground Control,250/275LBS. F&R. Adjustable Tokicos.Camber Plates in front,about 2.2 degrees neg.camber. Front strut bar "from weedeater" ^). Running only front bar at present approx.7/8s. I plan on installing MSA front and rear sway bars soon. It handes great on the track,but requires soft sidewall tires for street.for any semblence of comfort. Poly bushings thruout entire car.

Softer springs could be used for a little better ride....

 

David

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It's great that we're addressing handling issues for a car that's supposed to be "all straight line"!!!

 

I have a question for the cognoscenti: why are V8 Z cars reputed to understeer? Of course, this is a rather complex issue. But stripping it down to the essential details, nose heavy cars will tend to understeer, but tail heavy cars will oversteer. Things change if the rear tires are much stickier than the front, if the front suspension has different camber gain than the rear, if one end has a stiffer roll bar than the other, etc., etc. But in general, I'd intuitively expect a V8 Z with lots of engine "set back" to oversteer (and I don't mean torque-induced oversteer - that's a no brainer).

 

My car, with all that sheet metal relocation, has the crank pulley just over the steering rack, and the harmonic damper behind the front crossmember - and this is with a big block. With a hardcore (heavy!)roll cage, I expect a weight distribution of 45/55 (tail heavy).

 

The other issue that I wanted to discuss is that of lowering the car but keeping the engine fairly "high" under the hood, or lowering the engine with respect to the car, but keeping the car at essentially stock height. My oil pan is 9" deep, and I'm using a Lakewood bellhousing. It's a huge piece that really hampers ground clearance. Since I'm mounting the engine to the frame rails, and not to the crossmember, engine mount geometry is something to worry about. I wonder how low people have been setting their cars; for instance, what is the distance from the ground to the bottom of the frame rails under the floor pans, or from the ground to the steering crossmember?

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Guest Anonymous

hey mikelly or anybody with input. here is the deal , I am going to use my car as a daily street ride, just a few mods over stock 350,300hp or less.I want it to ride nice , and also handle the occasional red light hole shot,but nothin to radical, I dont want to pile a hole bunch of cash into trick suspension that I really wont need. but I would like to mabey change springs or do some less expensive and less time consuming upgrades to make her a little better. Now , keep in mind I dont have any strut experence. so laymens terms please.i have read all of this thread, just dont know how much of all these mods are nessessary for my application. thanks guys, i am learning tons from ya.

 

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74 260, early 350,K.B.pistons,edelbrock manifold,carb,and cam,202 cast iron heads.Let the transformation begin.

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If it were me, I'd buy a front 1 1/8 inch sway bar, got mine for $160 with mounting hardware and urethane bushings, and then I'd get a set of springs and Koni "D" Strut cartiridges from Arizona Zcar. Beware though, those cartridges only work on later model 260s and 280Zs. If your Z came equiped with the ugly 5mph bumpers, you can use the struts. Struts and springs will run about $350. Other than that, I'd buy some lower control arm bushings and a solid Differential mount for the car. Go to www.victoriabrittish.com and check out their Gmachine bushings. You can do it in steps, but what I would do is buy all the pieces and then put it all on at the same time. One other area to consider is lower ball joints and tie rod ends. They get abused over time and should be replaced on any car if you don't know their age!

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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Guest Anonymous

mike,, mine has some ugly bumpers on it , but I dont know if it is an early 260 or not. I have seen a couple of places while searchin that make mention of a 74 car and a 74 1/2. how do i tell which mine is ?

 

 

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74 260, early 350,K.B.pistons,edelbrock manifold,carb,and cam,202 cast iron heads.Let the transformation begin.

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If you have the ugly bumpers, that is the 74 1/2 model. I'm not sure of the exact date for the switch, but April seems to stick in my mind. That was the big switch to the new platform. I'd call up Dave at Arizona Zcar and see if he still has the Konis in stock, great price for them BTW! If he does, grab them!

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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Guest Carlissimo

When I set up my car (a 1973 240), I tried to retain the original level of handling and ride quality. I wanted a very fast street car that I would enjoy driving every day and would hold its own against an occasional Porche or Vette in the hills of Southern California. I had no plans to set it up for the track.

 

I added Datsun factory "Stage 1" springs and Bilstein struts. I do not have the numbers on the springs, but I recall they were supposed to be about 25% stiffer and about 1" lower than stock. I installed he engine as far back as it would go before the distributor hit the firewall. I have comp T/As - 245/50-15 on 8 inch wheels on the front and 265/50-15 on 9 inch wheels on the back. I have all new stock bushings and the stock sway bar.

 

The shocks and springs made an incredible improvement in high speed stability. The car is actually stable at speeds over 130MPH. The ride is very much like a stock 240 and nowhere near as rough as a Vette. I love the Bilsteins although I don't know if they make them any more. They are soft over small bumps but stiffen quickly when the driving gets aggressive. If you've ever driven a German car, yo uknow what I mean. It understeers a little in turns under neutral throttle. I like it this way though. It makes it real easy to steer with the throttle. Add power and the understeer changes to oversteer. It is a lot of fun blasting around on the street albeit, not the best for a track setup.

 

On the negative side, the car leans more than I would like. Am thinking of going up on the size of the front bar just a tad and adding a small rear one to try to keep the same balance that I have now. I know this will stiffen the ride somewhat, but will try not to go overboard. Also, the bump steer with the big tires is a little annoying. Am still trying to get rid of it. Any suggestions ?

 

-----

Carlo 1973 327 5-Speed

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Carlo mentioned "European car feel". If that is what you are looking for, then buy yourself a set of Boge struts. I used them for a little over a year when I blew out my 1st set of Koni struts and the Boges were sweet. They also come stock on Porshes, so you know they are quality pieces. I think MSA still sells them. As for Bilstien, I have their shocks on my lowered 1993 GMC Sierra step side and they work great. Truck handles so well that I have considered taking it to the road course to see what it would do!

 

Carlos, did you do the JTR mod to the lower crossmember? Drilling the hole for the lower control arm to change its mount location might help with your bumpsteer. Also, I'd try to get a 1inch or larger sway bar up front, and put atleast a 3/4inch bar in the rear. It will stiffen up the car noticably, but the plus side is the body roll will disappear!

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

 

[This message has been edited by Mikelly (edited February 23, 2000).]

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