Jons79

Just picked up a nice 1990 car to run as my dedicated autocross car. Previous owner has a ton of paperwork and included is the original window sticker. A $460 option of Performance Handling Package is listed. No reference to Z51 or anything.....

Just curious what that package consisted of? Big brakes? Etc?

Churchkey

A vehicle build list of RPO numbers is attached to the underside of the center console lid.

Reference them here:
http://www.corvetteactioncenter.com/...o/8496rpo.html

Some general info on Z51 package

RPO Z51 Performance Handling Package (1984-90, 1996)

Original Option Price: $350-1,295 (The latter price represents 1988 models, which included 17 inch wheels)

Much more common on C5s and C6s than it was on C4s, the Z51 package had a few small changes over its few years available on a C4.

1984 models: Heavy duty springs, shocks, and bushings, larger sway bars, fast ratio steering, engine oil cooler, and auxiliary fan.

1985-90 models: Heavy duty springs and bushings, Bilstein shocks, larger sway bars, fast ratio steering, and heavy duty cooling. Larger front brake rotors and calipers became standard in 1988, as well as 17 inch wheels. Both Z51 and base suspension spring rates were decreased in 1985 due to harsh ride compaints from the 1984 model.

1996 models: Heavy duty springs and bushings, Bilstein shocks, and larger sway bars. Heavy duty cooling options and fast ratio steering had become standard on all models at this point. Non-Grand Sport models also received 275/40/17 size tires on all four wheels instead of 285/40/17s in the rear, and 255,/45/17s in the front.

Option Restrictions: 1987-90 models required a manual transmission; Not available on a Convertible until 1996; 1996 models also required power seats, and Performance Axle Ratio, if ordered on an automatic car. Not available with FX3 or F45.

93Rubie

You have a good optioned car if it is JUST a Z51. If you have the FX3 package as well you have the base springs and bars on the car. Look at the RPO sticker as Churchkey mentioned. Look for FE7 on it, that is the RPO code for the HD suspension. J55 HD Brakes should be on there as well. Z51 should be listed near the end. Should be under your center console door.

If you want/need help for setting up that car for auto-x. I might know a thing or two.

Jons79

Looking over the options......it appears that it does have Z51 as well as the FX3. This car was set-up by the previous owner. The selective ride (FX3) shocks have been replaced with Koni adjustables and a larger front sway bar up front. (I'll probably upgrade the rear one). Other winter projects will be drilled/slotted rotors and replacing a few bushings with poly ones. Have great tires (Nitto NT01's 275/40/17's)all around.

Any other suggestions?

blackozvet

some info on springs and swaybars which can come in handy if your going racing ?

https://www.corvetteforum.com/forums...84-96-z51.html

93Rubie

That means you got the base springs, bars, and bushings. Stinks.

Good chart. http://www.netmotive.net/articles/hib/c4/sustunch.pdf

The Koni's are a great off the shelf shock. I really like mine.

Not sure a bigger front bar is what you want at all with those springs. Heck, I don't find myself wanting more front bar than the STOCK 30mm S on my 93 Z07.

Here is the thing about setting up a car, what works for me, may not work for you. Its a preference thing. My car is very neutral to a hair loose in higher speed auto-x. Lower speed its a hair pushy. At track speeds my front bar adjustment with the shims (see this posting: https://www.corvetteforum.com/forums...or-auto-x.html would be TOO loose but with NO shims its PERFECT for track days. ***The tire stuff in that post I wrote is out of date*** Bridgestone RE71R's or nothing!!! I'm on 18X9.5 C5 Wagon wheels with 275/35/18 RE71R's for 2015 and beyond.

If you do upgrade the rear go to a 24mm S or maybe the 26mm S if you keep your base springs. You really need to change the springs if you want a SIGNIFICANT upgrade in handling to the TRUE Z51 springs and bars.

Springs, then tune with bars to taste is the best option.

Honestly, it depends on how serious you are about it. You can run about anything but how fast do you want to go?

Closing thoughts: There is NO advantage in the drilled/slotted rotors. Save your money. Centric blanks from Rockauto.com for the J55 13" HD brakes are $50. FWIW, DO NOT replace the four "dog bone" trailing links with POLY. These have axial movement in them, they need rubber or a Banski type setup with heim joints.

The NT01's are a good sticky tire (especially with some heat) they seem to wear good from what I've seen from others who use them. Will bump you to BSP for SCCA stuff.

IDK, your skill level but seat time, seat time, seat time is everything! A properly prepared car helps too....

Good Luck and have fun!

Churchkey

Suggest leaving the front suspension alone until you have some seat time @ the track.

My set up for fast corners:
For the front: Soft spring(s), really good shocks & a big bar.
For the rear: Stiffer than stock spring, good shocks & a bar 1 or 2 steps up from stock.

Newer style brake pads do not gas as much as older style pads = drilled & slotted rotors are normally not required. If the rotors are glowing red convert to C5 brakes with drilled & slotted rotors. C5 rotors are thicker & will cool better + C5 calipers = better brakes.

Jons79

I know the previous owner ran this car in BSP and did quite well. (2nd overall for the season and many 1st place finishes at local events)for me.....I truly need to work on "the nut behind the wheel" as they say.

What mods I KNOW the car has;
Larger front sway bar (don't know size, but is massive looking);
Longer rear "lowering" bolts on rear (no wedges on front spring)- ride height seems good. If anything, possibly a HAIR higher in rear.
Harness bar/driver harness;
Nitto NT01's 275/35/17 all around;
Removal of smog pump;
A/C disconnect;
Koni adjustables on all corners;
Clutch/flywheel replaced with NON dual mass flywheel (noisy rattle from the ZF6!)
Top end of the L98 was completely rebuilt;
Lightweight cat and straight through pipes with no mufflers;

That's all I can recall and what I see. I may really just run the car as it sits for awhile and get good feel for it and what it's doing before I change much.

93Ruby - what makes you say drilled and slotted rotors with some good hawk pads won't show a difference? My 91 (albeit with 12" standard rotors) showed a great difference when I upgraded to D/S rotors and good pads. Just curious what your thoughts/experiences are with it.

93Rubie

If its a BSP car I would interested to know how much camber the front of the car has. That might be way the MASSIVE front bar.

That being said if its a BSP car, I bet it no longer has the stock springs/bars. I would get under it and look at the spring codes. They are a three digit letter code on the spring. That will tell you what you have (at least for factory springs). If they are aftermarket they usually have some sticker.

A bit higher in the back is what you want. That is a good thing.

Sounds like a fairly well prepped BSP car. I cannot imagine doing an A/C delete, top end rebuild, and the single mass FW, and NOT touching the springs and bars. I bet money its all changed underneath.

I was assuming this was a "stock" car. Being a BSP car means its FAR from stock in most cases.

The PADS is what made the difference. Drilled and slotted rotors do not do CRAP. In fact in most cases they weaken the rotor and they WILL crack easier under high heat use than a non-drilled/slotted rotor.

I'm OK with slotted rotors if you must but for the money a regular rotor is plenty good enough. This is auto-x not LeMans. Heck, talk to most track day guys (i've done a couple) they run regular rotors as well.

As far as pads go, lots of choices. I LOVE my Ferodo DS2500's they bite HARD even at auto-x/street temps but still modulate nice. Will do track days just fine on my mostly stock 93.
Things like the Hawk HP+'s are too grabby for my taste.

Yeah, based on those results. You may not want to touch ANYTHING until you can duplicate them. Seat time, seat time, seat time....

rorrapalooza

Not to derail a thread, but my 84 Z51 wasn't equipped with a second fan, and I'm 90% sure it doesn't have an oil cooler since I didn't find one when I replaced the radiator, though it does have a transmission cooler.

It was a very early one in production, so I guess maybe it was before those changes were made.

It also doesn't have a list of RPO codes anywhere... not under either of the storage bin lids and not under the center console lid.

WVZR-1

I'd suggest your own thread - this one is not relevant. If you have a very early '84 it might have an engine compartment tag. See this thread and maybe start your own inquiry posting your VIN. The AUX FAN wasn't an option in '84 but the oil cooler was. It was very different than the L98 cooler package.If you changed the radiator and only had a cooler in one tank then you're correct - "no oil cooler".

https://www.corvetteforum.com/forums...-bay-84-a.html

Kevova

the 89-90 z51 fx3 cars had the big bars just the base springs. Hib Halverson wrote an article about the 89-90 Z51/FX3 cars. The base springs are FHA the stiffer Z51 spring is FHB. Z51 came with oil cooler and HD cooling also.