my 84 has the z51 package according to gm that posted this package on a web sight advertisement for new 84 corvette sales. however i looked at my build sheet and window sticker and i didn't see the package. 40 mm sway  bars, cruse control, wide 220vr50 16 good year gaterbacks. 8.5 front 9.5 rear aluminum rims. and a stiff front and rear spring. however my shocks are black in color. not yellow. my 84 has a early production number 3,000. production date 3of 83. i looked on my production build sheet and window sticker, and didn't see the z51 package listed. only the cruse control and rims and tires. would the window sticker list a z51 package and cost on it? I'm  

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according to the Corvette Black Book for reference...the RPO Z51 IS listed as an option so therefore it SHOULD be on the window sticker as well....if you look at the options sticker on the underside of center arm rest...is it listed there? If not my guess is that maybe someone changed out the parts....are you sure you have the different sized rims on your car? you can also check the VIN number at Chevy dealer and the computer will tell you according to the VIN what options the car left the factory with.

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....Jeff

thanks I'll look under the center console lid. I'll check out my Vin number . as far as the window sticker in the options it shows the bigger rim and tire package.  it said it's a 84 corvette base coupe. with the removable see through top. the build sheet shows a bunch of numbers  like Au DE kt among others. the owners manual in the black cover that was in the center con, has a cass,tape Boise music system manual good year tire warn booklet, manual trans book, automatic booklet, among other information. the only thing i see missing is the pertecto plate. not sure if it came with one.     

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protecto-plates disappeared in the early 70's i believe....you can go to the internet and google vintage window stickers, there are companies out there that will make you a vintage window sticker like the one that was on your car at the dealer.....again look under lid of center console...should be a white sticker with all the RPO codes  for the options your car was originally ordered with, if RPO code Z51 is not on that list, chances are your car was redone after the fact...hang on to that cassette and other stuff....the cassette alone is worth some money especially to someone looking to present the car as "all original".

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....Jeff

The Z51 "perf " handling package didn't include cruise and only one size tire was available on all cars 84 - 87;
a GY  255/50 x 16
'84 Z51 had 25mm front/ 23 mm rear solid sway bars and springs so stiff they will shake your fillings out.
You would easily know if it is a genuine Z51 because no other C4 rode that hard
Following complaints , the  later cars got thicker bars ( 30mm /22mm ) and softer springs to improve ride quality while maintaining handling

From the description, Johnnyone's car is NOT equipped with Z51.

Z51 will be listed on the window sticker $600.24, and on the SPID which is in the LR cargo compartment in an 84.
Z51 includes Bilstien shock absorbers, which are yellow. (His are black).
Z51 includes B4P boost fan, the little forward fan in front of the condenser (He doesn't say). B4P was a popular option by itself too. Presence of the fan is not Z51-specific.
Z51 has a faster steering ratio. Very difficult to know the difference unless you've driven enough of both ratios to know, but back to back, the difference is quite noticeable.
Z51 wheel sizes are 8.5 front, 9.5 rear, with 255/50-16 tires. (ALL 84's have the 8.5's, and Goodyears, and is listed as an option on an 84 window sticker. "Base" wheels were never released on a C4).

And the big one. Z51 has different springs. The springs have codes. The rear Z51 spring is an 84-only spring. The code is on the LR side, on the bottom. It is easily observed. Z51  REAR spring code is: BMH.  Z51 FRONT spring code is: BMB but is a bit more difficult to find. Usually on the bottom, RH outer side.

Z51

A trained-eye can see the difference in front/rear wheel width, and the difference in ride quality of a car just running down the highway. I used to spot a 84 Z51's harsh ride without even being in it.

The spring codes are listed in boxes 15 and 16 on your build sheet.

BMB and BMH are Z51 codes. Any others are base suspension.

i looked on my build sheet boxes 15 and 16 my spring codes are bma, bmf. box's 17 and 18 tf, tl front and rear shocks.  my wheels px2 inch alum whls.  on my window sticker it shows qzd p255/50vr-16. box 20 steering gear aj.  box 21 stab bar di fa. when i bought my new tires for this car i bought Goodrich directional. it had the Goodyear gator backs on it. however when we took them off the rims they just fell apart at the beed. looked inside the tires they had bad cracks . not worth keeping at all.  the rims looked as if they where never taken off.  the fronts where 8.5 the rear was 9.5.  i sent the rims to keystone to have them recondition.  look rear nice now.  i think i don't have the z51 package.  it seams to be a base coupe.  as far as the ride goes it like driving a dump truck. very stiff indeed. this is my frist corvette. thanks for all of your input on this subject.

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BMA and BMF are "base suspension" spring codes.
Steering gear code AJ is the 15:1 "slow" non-Z51 ratio.
All 84's have QZD "255/50-16 with 8.5" alloy unidirectional wheels".
If you have 9.5" wide rear wheels, someone has changed them. The wheels are dated inside them. They have to be removed from the car to read the dates.

You have a base suspension, non-Z51 car. But that may be a blessing, as the 84 Z51 was a kidney bruiser. The fast steering is nice, however. When my ladyfriend and I were test driving Corvettes in early 85 prior to ordering and purchasing the one I still own today, we drove both Z51 and base cars. I noticed the steering ratio difference  straight away. I wanted Z51 for our car just to get the steering ratio. To me, it makes a difference in how the car drives and feels.

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One other thing, not related to Z51. You have a very early 84. On Early 84's, the cruise control servo was mounted ahead of the LF wheel, under the headlight (when the hood is open). Later in production (I don't recall exactly when) the servo was moved to the above the battery location where it remained through 96.

There was a campaign to relocate the early cars' servos to the above battery location. I don't recall the reason for the campaign, but I believe it was because the servo was getting wet from water coming in the headlight door opening, and causing "issues".

I'm curious whether your early car still has its servo in the forward position, or if it was changed in the campaign. (I'm not sure if it was a "recall" or not).

Cheers

FWIW ,
 the base (FE1) spring rate in '84 ( 63.5 N/mm front /72 N/mm rear) is slightly heavier than the Z51 spring rate (63.5 / 57 ) of '85

cruise control, is mounted above the battery. however there are holes in the left front head light, where the headlight relays are. also there is a bracket plate still there. makes me wounder if it was for the cruse control now that you mentioned it.  my production number is 3,000. built 3-29-83. the weather seals are different on this car. however i just replaced the ones that where bad with ome gm parts. they fit just fine. except the outer window seal sweep had to drill a hole to put a screw in. the original ones where about a 1/4 inch longer. there are three screws that hold the seals in place on the door. the thrid screw hole thats toward the very end of the rear of the door, was drilled out from the factory about 1/4 inch longer to hold the old seal. so i had to drill a hole 1/4 of a inch inward to hold the new seal. hope that made sense.as far as the rims go, you said it should have 8.5 all the way around. thats very possible indeed. however I'm going to check out the date codes. theres no need to change them out, if they had been replaced. at one time. in the beginning i was going to have this car judged. however the cost in doing that isn't worth it. even if this car was an top flight it still wouldn't be worth the money. it's just a driver to me now. don't take me wrong it's a out standing car for it's age.

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Any 84 built in 83 had the forward cruise servo. So yours has been moved.Most of them have been. I've only seen one 84 during Judging that still retained the forward position.

Non-Z51 have 4 8.5" wheels. So the 9.5 rear's have been added. Next time you have the wheels off, take a look at the dates. It's not a "code" at all. MM-DD-YY. Not tough at all.

If you want to learn more about your car than perhaps you want to know, take it to an NCRS Judging event. Your initial event is not "expensive". The expense begins if / when you decide to improve your score. But the initial outing isn't expensive at all. Don't change anything else, just clean it and take it out. I know C4 NCRS people all over the country. If you're interested, I'll put you in touch with someone local to you. Let me know, if interested.

Steering is one easy way to check if it is a Z51 or not, as this is not something that would normally be changed after shipment.  the Z51 cars are about 2-1/4 turns of the wheel, lock to lock, and the non-Z51 models are neary 3 turns lock to lock.

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There is no problem a little horsepower can't fix!

https://www.c4vetteregistry.com/member_uploads/14301_14400/14327/100_5963_zpse01892a52014510161358r.jpg

You can also take a look at the end of the steering rack. There's a "carriage bolt" looking thingy. If it has "AJ" on it, its the slow ratio. If it has "YP" on it, it's the faster, Z51 ratio. Requires use of a mirror.

Here's another Z51 tid-bit: Because the steering wheel doesn't have to be turned as far for the same radius turn (such as a sweeper, LH turn in an intersection) the turn signals on an 84-85 Z51 may not cancel reliably. On a standard suspension, they do because the steering wheel is turned further, and activates the cancel cam. The turn signal cancel cam was eventually changed for Z51 to cure this problem, but I'm not sure when. My April, 85 car has the slow-ratio cancel cam.


|UPDATED|1/13/2013 9:16:25 PM (AZT)|/UPDATED|