75 Z07

[William T.]

I have a 75 with L-82 4spd (M21) convertible with the FE7 package I was told by the seller that it also had the off road Z07 brakes. In trying to determine this the car does not have the dual pin calipers at present. Based on the #'s on the brake calipers it appears the calipers on the car are not the originals. For 75 is there a special bracket or just the dual pin caliper. Everything else on the car checks out as original. I've checked the alternator, fan, engine, heads, glass, carb, intake, exhaust etc, etc. So feel that the seller did not knowingly misrepresent the car.

[Joe L.]

Re: 75 Z07

I have a 75 with L-82 4spd (M21) convertible with the FE7 package I was told by the seller that it also had the off road Z07 brakes. In trying to determine this the car does not have the dual pin calipers at present. Based on the #'s on the brake calipers it appears the calipers on the car are not the originals. For 75 is there a special bracket or just the dual pin caliper. Everything else on the car checks out as original. I've checked the alternator, fan, engine, heads, glass, carb, intake, exhaust etc, etc. So feel that the seller did not knowingly misrepresent the car.

William-----

Basically, the only difference between a Z-07 1975 Corvette and a non-Z-07 which is equipped with L-82, M-21, and FE-7 is the HD brakes which were included with Z-07 but not otherwise available. So, whether the car was ever a Z-07 car depends entirely upon the installed brake system. The ONLY differences in the J-55 versus J-50 brake systems are:

1) front calipers with dual pad retaining pins, insulated pistons and HD, inconel-backed brake pads;

2) front caliper SUPPORTS cast GM #3948879 and 3948880;

3) rear calipers of standard configuration with insulated pistons and HD steel-backed brake pads.

There are no other differences. So, if all of the brake system calipers have been changed at some point, unless the front caliper supports remain, then there is no way other than original documentation to determine if the car was originally J-56 equipped and, thus, Z-07-equipped.

Quite frankly, as you can see from the above, it would be quite easy to "convert" a 1975 L-82/M-21 with J-50 and FE-7 to Z-07 "clone". Obtaining the brake parts might be a bit expensive but that's all there'd be to it. For 1975 with Z-07, I'd say that documentation would be EVERYTHING to confirm an original Z-07.

[William T.]

Re: 75 Z07

Joe,

So if I understand what you are saying there is a caliper support bracket that can be I'd by the casting # you gave me.

Thanks

[Dick W.]

Re: 75 Z07

An extra bracket that bolts on to the spindle and extends to the lower caliper attaching bolt, if I remember correctly. Used on all J-56 brake cars starting in 1968 or before.

[Joe L.]

Re: 75 Z07

Joe,

So if I understand what you are saying there is a caliper support bracket that can be I'd by the casting # you gave me.

Thanks

William-----


Yes, assuming they have not been removed, they should still be there if the car originally had J-56. It will look like that seen in the attached photos.

[Joe L.]

Re: 75 Z07

An extra bracket that bolts on to the spindle and extends to the lower caliper attaching bolt, if I remember correctly. Used on all J-56 brake cars starting in 1968 or before.

Dick-----


Yes, the caliper supports were used on all 1966-75 with J-56. However, there were THREE different sets of supports. The 66-67, 68-only, and 69-75.

[Dick W.]

Re: 75 Z07

I knew about the differences in the '68 and the '69 (spindle mounting bolt size) but I was unaware of the other bracket. Thanks Joe

[Joe L.]

Re: 75 Z07

I knew about the differences in the '68 and the '69 (spindle mounting bolt size) but I was unaware of the other bracket. Thanks Joe

Dick-----


Both 1968 and 1969 used the same sized bolts to fasten the steering arms to the spindle----1/2-20. 1965-67 used 7/16-24. I've never really understood why the 1969-75 supports needed to be different than the 1968. And, here's something else that has intrigued me for years:

The 1968-only right side support, GM #3925398, was discontinued from SERVICE and replaced by the 69-75 right side support, GM #3948880 in May, 1969. However, the 1968-only left side support, GM #3925397, was discontinued WITHOUT SUPERCESSION in May, 1975. So, apparently, GM considered that the RIGHT side 69-75 support could replace the 1968-only right side support, but they didn't feel that the LEFT side 69-75 support could replace the 68-only left side support. Now, that mystifies and intrigues me!

[John H.]

Re: 75 Z07

Here's what those J-56 brackets look like, on and off the car.

[Joe L.]

Re: 75 Z07

Here's what those J-56 brackets look like, on and off the car.

John----


I'm glad that you got your photos focused better than mine. When I clicked on my thumb-nails, I couldn't believe how badly out-of-focus my pictures were.

[Alan T.]

Re: 75 Z07

My 1969 vintage race car has those brackets and they appear to have been on there for a long time. I thought they were "real" pieces until I read somewhere that original brackets have the casting numbers raised as opposed to reproductions that have stamped numbers. Is that correct, do originals have stamped or cast in numbers?

Alan

[Dick W.]

Re: 75 Z07

If you will notice, Johns photo's show the numbers to be cast into the brackets.

[Alan T.]

Re: 75 Z07

I couldn't tell from the photos, still can't. Its real hard in photos to discern whether numbers are cast in (raised) vs. stamped (recessed). In that photo the numbers to me sure look like they are stamped and not raised, but I assume from your response that they are "cast in" means they are raised.

[Tony H.]

Re: 75 Z07

To me, they look cast in and sunken. One way to tell is by the shadows as well as the surface texture inside the numbers. A stamped number would look more crisp and the texture in the number smoother.

[Dick W.]

Re: 75 Z07

I guess you could call the casting number debossed, ie sunken numerals, vs embossed, ie raised numerials