scottmoyer

I've been reading up on what's needed to lower the '82 Z28 and upgrade the suspension to make it handle better. I've read a few times that people are replacing the springs, only to have the car sitting higher than before. I don't think that's possible with my '82, as it sits pretty high already.

But I wanted to verify the numbers before doing anything, so I checked the GM restoration packet for vehicle dimensions and it's way off. It states that the front end ground clearance is 12.4" to the lowest part, and the rear is about 14.6". That's pretty dang high right there!! The only height measurements that appear close are the front rocker panel to ground clearance is listed as 7.6" at the front and rear, and the total height of 50".

With a level set at the top, I measured the height at about 50", but my rocker panel measurements were slightly over 8 in the front and 8.5 in the rear. That tells me that if I order 1.5" lowering springs, I should be lowering my car! Would you guys agree?

My wheel well opening, at the center of the wheel is 27-1/8" front and 27-3/8" in the rear. Is 1.5" a good amount for the early 3rd gens, or is it too much? I plan on replacing the wheels with either 16" IROC-Z wheels or 17" IROC replicas. I will also be replacing most of the suspension, so I'm looking for advice, and pictures of lowered 82-84 Z28 and if you could provide details on the lowering, I'd appreciate it. Thanks

NoEmissions84TA

iTrader: (1)

WOW, that is a pretty car.

Look at your front air deflector. What is it, maybe 3" off the ground?
Are you ready to rip it off on every driveway apron and speed bump by lowering the car?

NoEmissions84TA

iTrader: (1)

Did you see this?

https://www.thirdgen.org/forums/engi...g-springs.html

TEDSgrad

iTrader: (4)

Most everyone likes at least -1.5", and some go -2".

You should attain an adj. Panhard bar once you lower. The purpose is to keep the chassis centered once lowered. It requires nothing else besides the bar - no cutting, welding, etc. (you can store your stock one). Beautiful car! Going back to pure stock will be easy.

Some folks have saggy springs, buy lowering springs and say that their ride height is elevated - duh. Springs will take a while to settle, so be forewarned that what you see initially is not the final product.

If you're going to replace suspension components, the two biggest are Koni yellows and strut mounts (I like Spohn's design, top dog is DSE if you can afford). The bushings in the strut mounts are probably toast by now. The taller strut mounts give back some travel of the strut after lowering. Shocks and the components to control the shock are the most important aspect of how a car handles.

Global West has excellent Delrin bushings for the stock a-arms. These will not be harsh. Do you have plans/ideas for what you want to do with the other bushings?

Everything I've described is unbolt, and bolt-in. Easy to reverse if required.

scottmoyer

I have a plan, but I don't know what sequence to do it in yet.

I want to lower the car some, because it sits high. Now, what does that mean with a 3rd gen? I need new springs and a panhard bar. I've been reading that I will want lower control arms, lower control arm relocation brackets, possibly a new torque arm and strut mounts. Obviously the bushings will need replacing, but do I also need to replace the upper/lower front control arms?

I also want to replace the engine/trans combo to have a 350/5 speed. The 145hp LG4 is very anemic and the 4 speed is not practical with this engine.

The car will continue to look the part, but I want it to handle and accelerate better than it does now.

TEDSgrad

iTrader: (4)

OK, that helps.
There are no upper/lower front control arms, just one arm. The previously mentioned Delrin bushings will work fine. One doesn't really need new tubular a-arms, but every little bit does add up if you're going max effort.
There is much debate over the bushings: rod ends are the performance choice, but are noisy, vibrate, and do wear over time; Del-sphere or Roto-Joint are a great street option; poly are better than stock rubber but do bind. I have poly on the chassis side for quiet, and Del-sphere on the axle side for max free movement. You may or may not need adjust-ability on the rear lower control arms - I like having my options. The PHB does not really matter for noise or vibration.
UMI is doing an excellent job of late, and Strano uses them on his site. Founder's is also a good option. Opinions vary, but watch where the knowledgeable people are going/using. No one company makes the best of everything, so you have to know how things are made (ex. - the Spohn strut mounts), and pick and choose what fits your application.
Rear shocks - I would consider looking into rear coil-overs (NOT fronts). The new shock technology is showing up big time, here. UMI has Viking and some new AFCO; RideTech has rears, also. These are all made specifically for around a 2" drop. If you buy regular Koni shocks for the rear, they will not be operating within their intended range due to the 1.5-2" drop. Personally, I like weight jacks for front, and coil-overs for rear - both have some adjust-ability to "get it right." Rear coil-overs only have 1/2" (maybe 3/4") adjusta-bility. Buy the right shock for the intended ride height! For the rear, the stock is 16" range, 13" collapsed, and 19.5" extended. If you want a -1.5", then subtract 1.5" from all three measurements and look for a shock that is very close to those new numbers.

Lowering a ThirdGen is a mixed bag. Yes it lowers the Center of Gravity (CG) which is a good thing . Then, you have to make sure your shocks are operating within the new operating range. With some planning and smart purchases, no big deal.
Attached is a crude pic showing original ride height in pink, and lowered in yellow. The dots are the CG. By lowering, you decrease the distance between the CG and the roll axis (distance between pink dot and pink line vs yellow dot and yellow line) - very good thing. But you will notice that the front Roll Center (front dot of the line) has dropped a lot; and the rear RC has dropped very little. So, the yellow line (roll axis) has greater inclination front to back than the pink one - not so good. This messes with weight transfer and the ability of components to deal with it. You fix this by welding a PHB extension bracket onto the existing bracket on the axle so that you can lower the attachment point for the PHB (slightly lowers the rear roll center). UMI sells one. Next, you get extended ball joints on the front, which will help to raise the front RC (you'll notice the yellow front dot on the yellow roll axis is right at pavement level. These two things help level the steeper roll axis inclination caused by lowering. Now you're golden: lower CG, shorter distance between CG and roll axis, and flatter roll axis.
Yes, weld on the LCARB's, too.

You should weld in sub-frame connectors. That's the beginning move - strengthen the chassis.

The TA will be decided with your new trans. I like it off the trans. You may/may not have a choice once you have the trans. Like you said, it's a sequence issue.

TEDSgrad

iTrader: (4)

A fellow moderator said this of switching from the Eibach lowering kit to Ground Control weight jacks:

t/aws61985

iTrader: (2)

I already have a non-adjustable UMI upper and lower panhard bar. Is A adjustable one really needed? I have a set of Ground Control weight jacks that I just bought. I too also want to get rid of the wheel to fender gap. The only Factory suspension part on my car is my K member. So I don't really want to spend money on a part that I already have.

TEDSgrad

iTrader: (4)

Absolutely!
When you lower the car, the axle is being brought up closer into the chassis. If you cannot shorten the PHB, what do you think will happen?

The chassis will be pushed out on the pass side because the PHB is still the same length. The rear end will not be centered in relation to the chassis anymore.

More importantly, you need to adjust the length of the PHB for the above mentioned RC adjustments (which is a great tuning tool).

If you want to adjust your suspension and tune your suspension, there is no other PHB to buy - an adjustable one.