[Ramairnacho]

Hi group I was viewing 12 bolts on internet and seen a 331 posi but listing said it was from.an ss camaro. I also learned that the ss and rs camaro had 5 rear leaf springs and z 28 and firebirds had 4. Are the perches a different depth. I asked a friend and he said they same but read on Facebook there different. How can I tell? Is code stamping the same? My other friend measured both of his and he says it should be 2 inch. But he bought his out of car. What is correct depth of perches for a pontiac formula, esprit or ta?

[Formulabruce]

IMHO, and I have owned both, I have found the SS Camaro deeper, but did not measure it. The last formula 331 I rebuilt recently had same perch as a 10 bolt here and I tested a spring set in it. You will find All the 12 bolts will have " Chevy" ratios as they are indeed a chevy designed product. I believe the designation for correct application came with a sticker that was put on the brake drum at sub assembly.
Another consideration is the thickness of the stock springs.
All considered, the shock plate lays FLAT against the perch with NO gap on ANY RWD ( car) rear end assembly to keep the center bolt , spring located under torque. I can get a measurement in a couple days on the Pontiac perch.
Just an FYI, you can put 30 spline axles, and carrier in a 10 bolt and have a rear as strong as a 12 bolt. The pinion is the same as a 12 bolt.

[72projectbird]

I can measure my original 1970 12 bolt tomorrow and report back.

[72projectbird]

On mine It looks like 2" from the base where the U-Bolts/T-Bolts mount, to the top of the perches.

Mine is original to the car, and has never been removed until I got it. The base plates that sandwiched the springs into the perches were nice and flat, not bent due to incorrect springs and rubber isolaters

[Transamric]

Originally Posted by Ramairnacho

Are the perches a different depth. I asked a friend and he said they same but read on Facebook there different. How can I tell? Is code stamping the same? My other friend measured both of his and he says it should be 2 inch. What is correct depth of perches for a pontiac formula, esprit or ta?

There is no difference between Camaro and Firebird spring perch depth regardless of whether it's a 10 bolt or 12 bolt. Yes, there were 4 and 5 leaf spring packs, but the total thickness of both was the same. 5 leaf packs used thinner individual leafs than the thicker, stiffer 4 leaf packs.
That said, measured about a dozen 1969 to 1976 housings just now, and they are all 1 7/8" perch depth.

And as was mentioned, 12 bolt rear assemblies were manufactured by Chevrolet Gear & Axle plant. So the codes used were the same, assuming that ratio was used in Firebirds. (such as the 4.10 ratio. Optional on some 1970 Camaros, but not on Firebirds.)

[Ramairnacho]

So I'm getting mixing thoughts on this. Some say camarro ss are deeper perches because of 5 leaf springs others say same. This is a bit confusing to me. If same the 5 leaf spring unit must be thinner material than the 4 leaf spring material to.rqual same thickness. Is it 2 inch space or 1 7/8?

['ol Pinion head]

Ric is one 100% correct. Have several original 70.5 F-body 12 bolts, have built many more.

The 70.5 F-body 12 bolt housings are just that, 70.5 F-body specific.
Camaros & Firebirds in 1970 came down the same assembly line. Smoothy Chevy style brake drums, Chevy style backing plates, 70.5-74 long parking brake cables... all the same.

IF the 70.5 Camaro had a different spec leaf spring pocket, those 12 bolts would have a different stamped ID code.

[Transamric]

Originally Posted by Ramairnacho

So I'm getting mixing thoughts on this. Some say camarro ss are deeper perches because of 5 leaf springs others say same. This is a bit confusing to me. If same the 5 leaf spring unit must be thinner material than the 4 leaf spring material to.rqual same thickness. Is it 2 inch space or 1 7/8?

Not sure where the confusion is.
1970 Camaro SS & Z28 as well as 1970 Trans Am, Formula and Esprits optioned with a 400 2bbl. all used the same dimension 12 bolt housings. No differences at all.

[Formulabruce]

1 7/8" vs 2" is just a matter of who and what ruler/ tape measure was used.
There has been so many Wrong aftermarket Thick 5 leafs springs tossed into our cars that when you see them not looking right. You begin to second guess. I had assumed the 5 leaf perches where deeper and probably saw some modified ones.
To this day , its tough to get " Stock" springs to sit correctly and ride right. Even from Eaton.

[Transamric]

Originally Posted by Formulabruce

There has been so many Wrong aftermarket Thick 5 leafs springs tossed into our cars that when you see them not looking right. You begin to second guess. I had assumed the 5 leaf perches where deeper and probably saw some modified ones.
To this day , its tough to get " Stock" springs to sit correctly and ride right. Even from Eaton.

Couldn't agree more.

[Formulas]

One time i was experimenting with 2 sets of leaf springs to make one,
I cut down a main leaf ( removed eyes ) to be the #2 leaf then moving # 2 to #3 spot and so on trimming the rear section of the springs to normal lengths thus giving me a stronger front segment for anti wrap up like a traction bar

Well i was messing around with a original 4 and 5 spring sets and i noticed this

the springs on #4 count were slightly thicker and had a sheet metal shim under the bolt going through the springs in perch area

the #5 count springs were thinner but more numerous and didnt need that sheet metal shim to achieve the desired thickness to get their desired clamp load at the perch