LeMans Pete

Can anyone provide a defined list of the Z07 package in 1975 and methods of identification?

What I know:

• Z07 option only provided on L-82s (and possibly only non-AC L-82s).
• Dual pin front calipers (not familiar, anyone have pics or a concise explanation?)
• 7-leaf rear spring
• rear sway bar
• M21 transmission

I started down this road a couple years ago when I identified the M21 transmission. I quickly dismissed it from the lacking rear sway bar.

But, during my initial phase of my restoration, I noticed the 7-leaf rear spring along with the 5469498-9 heavy duty calipers. My front sway is 15/16" if this makes any difference.

Any help identifying these items would be appreciated.

LeMans Pete

I've also read that the front coils were thicker in diameter. Would anyone have this specification?

garage-ghost

Easy Mike

Z07 required the L-82, M21, and included the FE7 package. Essentially it added heavy duty power brakes to the gymkhana package. FE7 included stiffer front sway bar, rear sway bar, stiffer front and rear springs, heavy duty shocks. It's possible the dual pin calipers were gone by 75, but don't quote me on that.

I'm not aware of any factory AC restrictions, so you could probably have Z07 with factory air.

Mike Ward

Dual pin calipers (AKA RPO J56 brake option) looked like this:



meaning that the normal single pin ear was machined off the caliper and holes drilled front and rear took their place to accommodate the two pins.

The pads looked like this:



I believe the pistons were also made of a different material offering better insulation properties.

...Roger...

I've only seen 2 sets of the J56s, 1 set real,the other was machined to take the duel pin pads.

LeMans Pete

Excellent picture Mike. My AIM lists the casting number 5469498-9 as the heavy duty calipers for the Z07 package, yet mine are single pinned. Any info behind the casting numbers?

Also, what is the diameter of the front sway bar?

hunt4cleanair

My information differs from that described by Easy Mike...RPO C60 was not an option when Z07 was specified. Initially (in 1973), was a re-packaging of F41 parts therefore it included the 15/16" diameter front bar GM# 3831972. This was specified in the 1975 Z07 mix. The rear-leaf was, as stated, a 7-leaf spring GM# 3977578. Front coil springs GM# 340519, broadcast code AA rated at 550 lb/in. And included the dual pin front calipers as described above.

A rear sway bar was not included, which was included with FE7 beginning in 1975. Prior to FE7, no small block were equipped with a rear sway bar nor did suspension packages provide one.

bobbarry

Just a question: what was the advantage of that pad setup, aside from the difference in piston insulation? The pads look to be the same size, and if anything, perhaps even more difficult to change quickly in a pit-stop than the single-pin setup.

earthquake68

That's funny, did you know the caliper pictured is the EXACT SAME as a HMMWV for the Army? On the hummers though, they are mounted in-board next to the differential. C-3 Corvette parts on a new hummer. Go figure.

Rowdy Rat

The AIM will list part numbers, not casting numbers. They are not necessarily the same.

To the best of my knowledge, these are the correct casting numbers for 1965 to 1982 Corvette brake calipers.

1965-Early 1967
5465954 (front, inner)
5465952 (front, outer)
5465902 (rear. inner)
5465905 (rear, outer)

Late 1967-Early 1972
5452270 (front, inner)
5452273 (front, outer)
5452281 (rear, inner)
5452284 (rear, outer)

Late 1972-1982
5473795 (front, inner)
5473796 (front, outer)
5473806 (rear, inner)
5473807 (rear, outer)

For Corvettes up to 1972, there was no difference in the casting number for single or dual pin calipers... The single pin mounting boss was milled off and the two holes for the new pins were drilled by Delco for the heavy duty caliper application.

While I'm not as well versed on the later C3s, if I had to guess, I would say that the 1973-1975 heavy duty calipers used the same casting as well.


The advantage was that it kept the pad from warping in a racing environment. If I recall correctly, the original backing plates for the pads were made from inconel (an extremely heat tolerant alloy) and the plate itself was bent 90° at the top to further add to the rigidity of the pad. The resultant bend required the original mounting boss be removed... And the addition of two holes for the new pad pins.

The pads haven't been available for some time now, but when they were, the cost was outrageous... List price was about $400 an axle set back in the late 1980s.

Regards,

Stan Falenski

LeMans Pete

Thanks Stan, you are correct as my casting #s do not match the part #. I read the 5465902 on the passenger rear and going back to the AIM, the part # was similar and got them mixed up.

Off my '75, these are the casting #s I have:

Driver Front: 5473795
Pass. Front: 5465952
Driver Rear: 5473807
Pass. Rear: 5465902

I find it interesting that my passenger front and rear are listed in your '65-early '67 section, and more so that they are not on the same position. I'm assuming "inner" = driverside. My driver front and driver rear have correct castings per the year, but according to your info are not on the proper wheel.

LeMans Pete

F41 were the HD shocks, were they not? Did you mean FE7 above?

I'm interested to know where you found AC was not an option if Z07 was an option. Also, what about power windows (A31)?

How can the front coils be identified as 340519s?

Lastly, what is the diameter of the stock front swaybar?


Can you clarify this statement? Was a rear sway bar included or not with FE7 in 1975?

Paul Borowski

...when I did my '75 L-82 Survey some years ago, I had 4 to 6 '75 L-82/M-21 Z07 cars in it. I had over I think 71 L-82 cars in the survey.

....most of the Z07 cars were fully loaded cars, I believe 2 out of the 6 cars I had were non A/C cars. One was a non A/C, radio delete car which was cool. The only option it had was the L-82 with the Z07 package.

...at McDorman's Auction late last year, he had a 187 mile 1975 Flame Orange Z07 roadster that had every possible option in '75 including Black vinyl hdtp and the convertible top had never been in the "up" position!!! It sold for $50K.

hunt4cleanair

Both were heavy duty suspension systems and included HD shocks. GM# 4984578 was the FE7 rear shock while 4940607 was specified for the F41 rear shock. I don't have info for the front F41 shock GM#.

Paul's survey suggests what he discovered during field observation and study while published sources, such as the Corvette Black Book state that AC was not an option when Z07 was ordered. Its well known that "recommended" packages were not always followed...Corvette buyers could get what they wanted.

Not sure if tag is removed. I supposed there might be a way to measure coil diameter and its rating but that's too techie for me.

Early C3s small blocks were equipped with a 3/4" diameter bar while 1975 and up were equipped with a 7/8" bar. Big blocks were equipped with 7/8" bars...same GM# was specified for 1975+ small blocks...go figure!

Yes...GM# 351597, a 7/16" bar.

LeMans Pete

Great info, thanks

Rowdy Rat

You're welcome!

First off each caliper is comprised of two castings... Eight per car. "Inner" refers to inboard, that is, the section facing toward the center of the car, outboard refers to the section facing out, away from the car.

I find your casting numbers a bit odd as well. The early caliper housings as I recall had a piston guide as part of the casting. Later, it was determined that the guide was unnecessary and different castings were created (the second group) that eliminated the guide.

Having said that, the guide can be removed and most C3 Corvettes have had their brake calipers refurbished at least once by now... It wouldn't surprise me if one of the rebuilders took care of this while sleeving the calipers. It also wouldn't surprise me if the castings were mismatched during reassembly. Outside of the previously mentioned guides in the early calipers, they are basically interchangable among each revision.

Regards,

Stan Falenski

ncrs41296

I own one of the 144 Z07 optioned cars in 1975. My car is a 14k miles Z07 convertible. What can I help you with?

ncrs41296

This car has been under NCRS nut/bolt restoration since 2004. Presently the car is apart/ frameoff. The no hit body is on a body castor and the frame has been blasted and repainted with GM104. The motor has just been completed and is presently having all the accessorys installed.
Since the passing of my NCRS head judge in 2008 (Marvin Burnett) I have slowed on the restoration. This car, with a build date of July 11th 1975 is the LAST Z07 convertible built. Mr. Burnett, upon seeing the car for himself at the NCRS winter meet in Janruary 2008 took pictures and agreed it was the last. He had never seen a Z07 built after April of 1975.
Built anytime in 1974/1975 the car did not hold a RPO distinction thur VIN numbers. So your tank sticker/build sheet/dealer copy is the only way verifiing this rare option. 1975 was the last year of this RPO option.
Car came in Coupe/Convertilbe.
L-82 motor came in all cars.
You could order A/C with this option in Automatic.
4-speed cars were M-21 Bourg-Warner transmissions with Heavy Duty 3:73 rearends. YOU COULD NOT ORDER A/C WITH A 4SPEED.
Oher specs were J-56 braking systems front/rear. Twinpin brake calipers on the front and single pin metalic pads on the rear. F-41 HD front and rear stablizers. 15/16 front and 3/8 on the rear. 27 inch single core brass radiator HD cooling syster. Rear shocks did have big hats on the top.
At 144 built in 75, it far surpassed the totals of both 1973/1974. Let me know if we can trade information anytime. Cleveland- NCRS41296

Paul Borowski

....I do not believe you could get an automatic with Z07.

...you could get other rear end ratios with the Z07.

....4 of 6 Z07s I have seen had A/C.

....you must have a fairly late convertible and your claim is probably pretty legit. I had a '75 L-82 coupe VIN#35026 that was a July 12th build date car and the LAST 1975 roadster(White/Red interior L-48 automatic car)was VIN#35199 and had to have been a July 13th or 14th build date car.

...I had to dig through my '75 L-82 Corvette Survey that I did from about 2000-2008 to find some of this info. I have something like 68 out of 2372 cars. A small sampling I know, but I have some fairly neat info.