1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

[Richard F.]

I'm the original owner of a 1974 L82 Z07 Corvette (Nov.10 1973 build), it did not come with the rear sway bar or rear heavy duty calipers as per May 17 1974 specification sheet/book. I know in general that the rear sway bar came standard on BB, and not on SB as it created an oversteer condition on SB. I assume the heavy duty rear brakes were necessary on BB and not on SB.

My question, is my L82 minus the rear sway bar and heavy duty rear brakes because it's an L82 as in previous explanation or because it was an early build, did G.M. add either one to the L82 after the MAY 19, 1974 Specification book?

Are you confused yet?

Thank You

[Joe L.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

I'm the original owner of a 1974 L82 Z07 Corvette (Nov.10 1973 build), it did not come with the rear sway bar or rear heavy duty calipers as per May 17 1974 specification sheet/book. I know in general that the rear sway bar came standard on BB, and not on SB as it created an oversteer condition on SB. I assume the heavy duty rear brakes were necessary on BB and not on SB.

My question, is my L82 minus the rear sway bar and heavy duty rear brakes because it's an L82 as in previous explanation or because it was an early build, did G.M. add either one to the L82 after the MAY 19, 1974 Specification book?

Are you confused yet?

Thank You

Richard------

1974 Corvettes with small block, regardless of whether equipped with Z-07 or FE-7 were not equipped with a rear stabilizer bar. Through 1974, the rear stabilizer bar was part of the big block option and not part of any suspension or performance option. After 1974, things changed.

As far as brakes go, all 1974 Corvettes with Z-07 were equipped with heavy duty brakes, front and rear, and regardless of whether the car was an L-82 or LS-4. No Corvette was ever equipped with rear-only heavy duty brakes (and, no Corvettes were ever equipped with front-only heavy duty brakes). The only way to get heavy duty brakes on a 1974 Corvette was to also order Z07. As a matter of fact, Z-07 was essentially only FE-7 plus heavy duty brakes. That's it.

[Richard F.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

Thank you for your response, and all input is important, I special ordered this Z07, I am the original owner it's never been out of my possession, 19,000 mi. I have all original documentation, all original parts (exception maintenance parts) delivered dual pin Heavy Duty Front Brakes Only standard single pin rears. You don't suppose G.M. could have stiffed me on the rear brakes?

Thank You

[Joe L.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

Thank you for your response, and all input is important, I special ordered this Z07, I am the original owner it's never been out of my possession, 19,000 mi. I have all original documentation, all original parts (exception maintenance parts) delivered dual pin Heavy Duty Front Brakes Only standard single pin rears. You don't suppose G.M. could have stiffed me on the rear brakes?

Thank You

Richard------

The rear brake calipers with J-56 Heavy Duty brakes were single pin; only the front Corvette J-56 brakes used the "dual pin" calipers. This is true of all 1966-75 Corvettes with J-56 brakes. However, the original J-56 rear calipers did have pyroceram insulated pistons and were equipped with special HD brake pads. If your rear calipers don't have these features, then you got cheated.

[Richard F.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

Thank you for the clarification, are the rear pistons on the heavy duty rear brakes the same diameter and should the rears have an extra bracket reinforcement as the fronts? (So I do have HD rear brakes)

Again thank you!

[Joe L.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

Thank you for the clarification, are the rear pistons on the heavy duty rear brakes the same diameter and should the rears have an extra bracket reinforcement as the fronts? (So I do have HD rear brakes)

Again thank you!

Richard-------


The rear J-56 pistons are the same diameter as rear standard pistons. The front J-56 pistons are the same diameter as front standard pistons. The only difference is that the J-56 pistons, front and rear, have a pyroceram insulator on the front.

The rear J-56 calipers do not have a support bracket as do the front J-56 calipers.

[Richard F.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

That will verify my originals, very helpful information. When I saw my rear calipers were single pin I thought they were standard calipers.

Rich

[Tom R.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Joe

That will verify my originals, very helpful information. When I saw my rear calipers were single pin I thought they were standard calipers.

Rich

So Richard, your rear and front brake configurations is that typical of J-56 of all J-56 heavy-duty brakes 1966-75?

[Richard F.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Yes, the only difference I can recall is the earlier J56 brakes had thinner pyroceram insulators, but as Joe stated the fronts were dual pin and the rears were single pin, both had the pyroceram insulators and HD pads.

Joe, did I miss anything?

Rich

So Richard, your rear and front brake configurations is that typical of J-56 of all J-56 heavy-duty brakes 1966-75?

[Joe L.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Yes, the only difference I can recall is the earlier J56 brakes had thinner pyroceram insulators, but as Joe stated the fronts were dual pin and the rears were single pin, both had the pyroceram insulators and HD pads.

Joe, did I miss anything?

Rich

Rich------


All 1965-E1967 Corvette calipers were equipped with pistons with pyroceram insulators. This included both standard, J-50 power, and J-56. These were thinner compared to later. The pistons were also of the guided type for all 65-E67.

For L67-75 only J-56 were equipped with pistons with pyroceram insulators. These insulators were much thicker than the earlier type. No L67+ calipers or pistons were of the guided type.

[James G.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

The backing plate for the HD pads are made from ICONEL - Iconel is non magnetic and doesn't transfer heat like metal does- thus a magnet is the easiest way to determine if the HD Iconel backers are present.

[Duke W.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Richard------

1974 Corvettes with small block, regardless of whether equipped with Z-07 or FE-7 were not equipped with a rear stabilizer bar. Through 1974, the rear stabilizer bar was part of the big block option and not part of any suspension or performance option. After 1974, things changed.

From '63 to '74 all HD suspensions included a 15/16" front bar. Big block HD suspensions in those years have the same rear bar, 9/16", as base BB suspensions. For 1975 the HD suspension (small blocks only since the BB was no longer available) was equipped with a 1 1/8" front bar and 7/16" rear bar.

Over the C2/3 production run a total of five front bars were designed and two rear bars:

Front

3/4" all base SB through '73 (?)
13/16" all base SB '74(?)-up
7/8" all base BB
15/16" all HD through '74
1 1/8" '75-up HD

Rear

7/16" '75-up HD
9/16" all BB, base and HD

The wide variety of OE bars makes suspension tuning easy with OE parts. Anti-roll bars increase/decrease bar contribution to roll stiffness by the FOURTH POWER of diameter, so even a 1/16" change makes a noticeable difference in dynamic response.

I may have the year of the change in base SB front bar from 3/4" to 13/16" wrong, so if anyone can verify, please chime in.

Duke

[Joe L.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

From '63 to '74 all HD suspensions included a 15/16" front bar. Big block HD suspensions in those years have the same rear bar, 9/16", as base BB suspensions. For 1975 the HD suspension (small blocks only since the BB was no longer available) was equipped with a 1 1/8" front bar and 7/16" rear bar.

Over the C2/3 production run a total of five front bars were designed and two rear bars:

Front

3/4" all base SB through '73 (?)
13/16" all base SB '74(?)-up
7/8" all base BB
15/16" all HD through '74
1 1/8" '75-up HD

Rear

7/16" '75-up HD
9/16" all BB, base and HD

The wide variety of OE bars makes suspension tuning easy with OE parts. Anti-roll bars increase/decrease bar contribution to roll stiffness by the FOURTH POWER of diameter, so even a 1/16" change makes a noticeable difference in dynamic response.

I may have the year of the change in base SB front bar from 3/4" to 13/16" wrong, so if anyone can verify, please chime in.

Duke

Duke------


According to GM, it's like this:

Front Sway Bars:

1963-72 SB except F-40/F-41-----GM #3831971-----3/4" (replaced by GM #3871318 for SERVICE September, 1983)

1973-74 SB except F-41-----------GM #334930------13/16" (discontinued from SERVICE without supercession October, 1982)

1975-79 except FE-7--------------GM #3871318-----7/8" (discontinued from SERVICE without supercession October, 1992)

1975-79 with FE-7, 1980-82 ALL--GM #351596------1-3/32" (discontinued from SERVICE without supercession February, 1999)

1963-74 ALL w/F-40/F-41---------GM #3831972-----15/16" (replaced for SERVICE by GM #3871318 June, 1975)

1965-74 BB-------------------------GM #3871318-----7/8" (discontinued from SERVICE without supercession 1October, 1992)

Rear Sway Bars:

1965-67 all BB------------GM #3871324-----9/16" (available in SERVICE only as GM #3872451 with bushings; replaced by 3923676 1/71)

1968-E1969 all BB--------GM #3923676-----9/16" (replaced for SERVICE by GM #3967713 February, 1972)

L1969-74 all BB-----------GM #3967713-----9/16" (discontinued without supercession June, 1986)

1975-82 all with FE-7----GM #351597------7/16" (discontinued without supercession July, 1996)

[Duke W.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Thanks for filling in all the details, Joe. The 352596 front bar is listed in the Chevrolet Power Manuals from the seventies as 1 1/8". Though many are discontinued they can probably be sourced, used, from the usual used parts vendors if anyone wants to do some chassis tuning. Also different size bars require different pillow block bushings (also listed in the Power Manuals and parts catalogs), but most of them are probably discontinued, too, so used, repros (if available,) or roll your own are the choices.

Duke

[John D.]

Re: 1973/1974 Z07 Rear Sway Bar/Rear Heavy Duty Brakes BB Only ?

Very informative thread. Were there any rotor differences for the HD brakes ?. Also at 19k the car would likely have it's original rear pads-no ?