To answer a few questions these are all just my opinion, not fact.
The ZL1 lid wont fit under the hood by any stretch of the imagination. Also, I am not a fan of the hoses coming right out the front of the engine.
The truck arm is not a very tunable setup and needs to be done with some flexibility in the arms themselves. They are not easy to execute in the aftermarket.
The Factory trailing arm setup / semi triangulated setup is not a bad start, however the front mounted shock, rear mounted coil spring, zero adjustment and soft bushings are all what stopped me from keeping them. They are difficult and complicated to make work with a coilover.
I have consulted with a few friends and discussed my application with them. The general consensus from people who build fast track cars was to add adjustment to the panhard bar mount, and increase the travel of the rear shocks if I could.
Since there is not much if any information out there regarding this I figured I would share what I am doing and why and where I got my information from.
I have taken a few of Ron Suttons classes, they are very good and he is a great reference when it comes to going fast, he understands the limits of working around an existing chassis. He has an immense write up on Lateral G that outlines a lot of what he covers in his classes. If you have a few days to kill read up on it, its an epic write up.
http://lateral-g.net/forums/showthread.php4?t=42423
The idea he promotes is getting the front suspension dialed in with the property geometry and use the rear suspension to tune it for a well balanced car, thus including some adjustment in the rear suspension is key.
Being able to adjust the panhard bar, both height and angle is one of the keys to being able to make the car handle better, it drastically effects the roll center of the chassis and can add or remove grip with just a slight height adjustment. This is after you have the right spring rates, shock valving and all the other things to make a car handle. This is how you make an ok car great, or great car outstanding. You can make it loose, tight or neutral with just these adjustments.
So knowing what I know, I should have ditched the stock panhard bar and mounts before I even started but I got lazy and wanted to move on. Good thing I have some good buddies that said cut that **** out and do it over with an adjustable panhard mount ya jack ass.
I cut off the stock mount and have ordered a slotted style panhard mount for the rear axle, I am hoping it will work well with what I have so far, but am not afraid at all to chop it up.
I will be building my own panhard for the rear of the car, using 1.25" DOM tubing with weld in bungs, 5/8-18 LH for the chassis side, 3/4 RH thread for the axle side. These parts are all commonly available. I am running high misalignment on the chassis side to bush the 5/8" hole down to 1/2" or near the stock size panhard hole. The axle side is just 3/4 bolted on no misalignment needed.
The new panhard will not have a bend in it, will be straight and hopefully allow me to keep the beefed up aluminum moser cover.
So now we move on to getting some more shock travel. Down travel was not going to cut it, so up we go.
After lots and lots of careful measuring and putting this off, I decided to cut into the lower rear framerail of the car and french the shock mount up in the rail. If my calculations were right, this will raise up my shock mount about 1.5".
It was an absolute horrible job on the first side, the second side I took a different approach and it was much more tollerable.
The upper shock mount ended up dead centered front to rear in the rear frame crossmember, this worked good for through bolting through the frame. The first side I did I drilled 4 small holes and connected with a small cutoff wheel, then used a die grinder and deburring bit to open the hole up for the clearance I needed. The second side I located the front edge of the opening and the rear edge of the opening and used a 1.5" hole saw, drilled two holes and used an air saw to get me close, then finished up with the die grinder. It took a fraction of the time.
In case anyone is wanting to do this on their own, the inside of the framerails when cut open measures 1.95", so whatever shock you are going to use, get or build spacers to make your upper shock mount that width, I need to turn a couple spacers still.
I used the same 1.5" hole saw to drill an access hole in the crossmember to access the nuts of the bolt for the shock, this is just big enough to fit a modified wrench up in to tighten the bolt. I do not believe that this hole has any effect on strength of the crossmember.
You can see in this photo that I had to take a little bit off of the bottom of the outside of the framerails in order to give the shock the clearance it needed to swing in all directions and have lots of clearance. I am working off of the garage floor so this is not a fun job by any stretch of the imagination.
So with the access needed, the holes all cut, I wanted to reinforce not only the outside of the frame rail, but also to reinforce the bolt going through the framerail.
So I came up with these guys, I believe it will stiffen up any of the strength I removed and spread the load out on the framerails just fine.
The frame has a slight contour to it so these plates need a little bend in them.
These are just .120 mild steel plates.
Here you can see the clearances I will have, this is more swing than the shock will ever have.
I am going to return the 4.1" travel rear shocks and substitute a 6.1" shock in its place, I will be sticking with the Ride Tech shocks. If you took the time to read through the Ron Sutton write up , it is one of the very few quality shocks built in the US and is totally tunable.
Is this perfect, I am sure its not, is it something I believe I can work around and make fast around a track, I think so.
For those of you that are still reading and want to know what kind of measurements this is. This is built at a ride height of 4.5" to the bottom of the pinch weld on a 25" tall tire, 3" of uptravel and 3" of down travel (Assuming that I dont have to limit the uptravel once its all in the car. Keep in mind with the chocks are behind the axle so actual centerline travel of the rear suspension will be slightly shorter than that.
Brakes for the rearend showed up, backing plate bracket is wrong, so those need to go back but they look awesome.
Hope that parts show up this week to get this all buttoned up, I am so sick of crawling around under the back of this car.
Sean