mbfan72

Car came with Z52 package and 700R4 auto transmission. ABS never worked and has not been fixed. Motor and transmission stock.

Changes to date:
Urethane bushings (all)
Cross brace (between lower frame rails)
Aftermarket rear camber struts
Corvette Challenge springs
Bilstein Z51 shocks
Z51 sway bars (30mm & 22mm)
17” wheels with Dunlop Direzza Z1’s (265-40-17)
Hawk HPS brake pads
1 degree rake front to rear
Wheel weights: LF 836; RF 843; LR 765; RR 743 (without driver)
Front camber -1.5
Front toe +1/8”
Rear camber -1.0
Rear toe -1/8”
Front ride height stock

There are a lot of choices about what to do next and I have a limited budget so I am looking for the biggest bang for the buck. Should I be looking at adjustable shocks, bigger front brakes, offset lower A-arm bushing to increase camber, repair ABS, lower the front (can be dropped about ¾”), or something else?

Solofast

First and foremost, what class and what organization are you running with??

rfn026

The car is pretty close to what you need. The problem is that you're probably on the edge of a class. Once you determine who you're going to run with and what class you're in you can make some changes. Also, do you plan on staying to local events or do you want to go national?

It's sort of amusing that the local cars are usually a lot faster than the cars that get out to the nationals. Something about tech and the fact the guy parked next to you knows what you're up to.

Richard Newton
Car Tech Stuff

mbfan72

The Winnipeg Sports Car Club - we use SCCA rules.

The car is classed as BSP-S (17" wheels were not available in 87)

We just run local events and Corvette only events.

At this point we can change anything and not change our class with either group.

Gas Junkie

You can remove a good bit of weight by taking out the A/C (must leave the heater for Street Prepared) and the radio.

mbfan72

The A/C compressor was on its last legs so I pulled it and put in the A/C delete pulley. I kept the heater just so I could defog the windows in the rain.

Solofast

A bit more negative camber at the front would be the biggest cheap thing you can do. That's just a set of LCA bushings. You need about -2 degrees up front as a minimum.

At this point, as anyone who has built a BSP car can tell you you've exhausted all the inexpensive things and to get to the next level, a top flight street prepared car gets expensive.

Probably a set of double adjustable shocks is called for.

One other thing that really helped the front end bite at lower speeds is a good dose of caster. I noticed this on the stock cars. Guy Ankney made a set of upper control arm bushings that allowed his control arms to be moved aft about an inch. It added a lot of caster and his car won more than a few nationals with that setup. When I asked him about the funny bushings and added caster he got real evasive, he hemmed and hawed a bit, wouldn't look me in the eye and said... "well, ahhh, it didn't help.... all that much".... Something to try and not too expensive.

In SCCA the 17 inch wheels are legal in BSP. They were available in other years and the updating and backdating rule applies. Cars on the same line can update and backdate parts, so even though your car came with the 16 inch wheels, the 17's are legal.

rfn026

I try to fun at least 6-degrees of caster and over -3 degrees of front camber. That's for a track car though.

Richard Newton

mbfan72

Thanks for the camber and caster suggestions. The offset lower A arm bushings are cheap.

I asked my alignment place to give me as much caster as possible but they only got about 5 degrees. Does anyone sell offset bushings for upper A-arms to get more caster or do you have to make your own?

I saw some QA1 single adjustable shocks - as opposed to double adjustable - are they worth considering at all?

Buying double adjustable shocks would push the budget a fair bit. Are they fairly straight-forward to set? I am worried that I'll spend the $ and then never get them set right.

Thanks

Solofast

You have to make your own, but as you have found 5 degrees of caster is low for an autocross car. The more steering angle you use at high g the more caster you can use. The offset bushings can help that too, by setting the rear lower rear front bushings to the max it will help with caster. I'd try that first.

Nobody who is serious that I know of has ever used QA-1's, they are mostly a drag shock.

Shock tuning is a art, if you want to get to the next step you have to learn how to do it and what each thing does. The first time you try you'll likely screw it up big time.. It just takes a while to get it right. Look at the tuning guide on the Bilstein site and that should get you started.

l98tpi

Since you have a limited budget, but we don't know how limited in term of dollars, you could first lower the front and the rear as much as possible but do keep a neg rake, rear sitting a little higher than the front. Optimum is 4 degree neg rake.

Another good upgrade would be some DOT Race Compound tires, especially if you are running BSP. And some HP+ pads will be a good upgrade too.

93Rubie

Not sure these are BSP legal, just FYI.
Also, I've been running the Dunlap ZII's in 255/40/17, work pretty good. No complants for a street tire.

How did you corner weight your car?
Also, you might move your battery for better weight balance yet.

More POWER=Headers, intake,tune.

mbfan72

I was fortunate that the shop that does my alignments had a set of scales. Since then someone in our club purchased scales and rents them out.

Thanks to everyone who took the time to respond - I'll start with camber and caster and see how that goes.

Just looking at the car's front suspension the upper A-arm mounts on a "rod" (sorry -don't know what the correct name for it is and I'm away from my shop manual) that bolts to the car. Rather than fooling with the A-arm bushings could I get a slot machined into that rod so that it could moved to get caster?

Solofast

Not legally in SCCA or NCCC.... That's why Guy made the bushings to effectively do the same thing, it moved the control arm back on the rod, but the rod bolted into the same place on the chassis.

It's probably less important since you have the earlier front suspension anyway. I'd just try to use the offset bushings to get as much caster that you can. If you get 7+ degrees you are fine.