Aftermarket Spring Perches

[scotty1320]

I've recently started restoration of my 67 and need to replace the spring perches on the rear axle.  It's a mono-leaf car and I want to return it to it's original configuration, so ordered aftermarket mono-leaf perches.  What I received doesn't fit well at all.  They were made to fit a 3-1/2" o.d. axle tube...not the 3" found on a GM 12 bolt.  Also, the hole pattern doesn't match the GM lower shock plates that I have.  The perch hole pattern is roughly 1/4" wider (left to right) than the GM plate.  I called the vendor and they confirmed that the perches are made to fit a 3-1/2" tube, which I believe the Ford 9" and Dana axles have.  They weren't sure about the bolt pattern issue.  Their lower plates probably match their perches fine, but I wanted to use my original GM plates.

So, does anyone know where I can purchase good quality mono-leaf spring perches for my 67 that fit the 3" tube on a 12 bolt?

Sorry if this has been covered before.  I'm new here and searched but couldn't find anything.  Thanks.

[ko-lek-tor]

Don't know what part of the country you live in, but it looks like the perches are somewhere between $70-90? For that money, around my area(Ohio), you could buy a 10 bolt rear or it may cost a little more and cut the perches off. Then, you would know for sure they would fit and be right.

[KurtS]

That's my thinking too. Maybe place an ad - someone may be cutting off monos to install multis or they have a junk axle they can rob.

[68 Ragtop]

So, does anyone know where I can purchase good quality mono-leaf spring perches for my 67 that fit the 3" tube on a 12 bolt?

Sorry if this has been covered before.  I'm new here and searched but couldn't find anything.  Thanks.

Did you try Ebay/Summit Racing/Moser Engineering?

http://www.ebay.com/itm/Moser-Eng-Leaf-Spring-Perches-Steel-3-Dia-Axle-Housing-2-1-4-Width-GM-7210-/191428770660

[scotty1320]

I'm a little embarrassed I didn't think to look there first!    I'd been looking only at the camaro restoration sites and they don't publish the axle tube size that their perch is made to fit, so that's how I wound up with some that didn't.

Thanks for all the suggestions.  I'd rather have new perches as I'm afraid the perches cut off another axle wouldn't fit very well by the time I got them cut off.  My skills with a torch leave a little to be desired.

[JKZ27]

Make sure you weld them on correctly as there are a lot of angles involved, if you didn't already know.

[scotty1320]

I know there's been a lot of discussion about pinion angles, and I read a discussion about 6 degrees positive (above horizontal).  Another site had a photo of an unmolested 10 bolt with a positive 5 degrees with the mounts horizontal.  I realize the perches aren't horizontal in the car, so the pinion angle becomes less when installed, and increases when the car is under acceleration.  Drag cars sometimes have the pinion angle decreased...or negative from horizontal...to accommodate the "extra" rotation when launching.

I also noted the perches are set inward to the front 2 degrees per side.

Does any of this sound screwy?  Are there any other things I'm missing?

[ZLP955]

I bought the Moser perches, just be aware that you will probably need to ream the bolt holes out a little for a bolt to fit cleanly, as the perches seem to be manufactured with the holes drilled first and then the plate folded into shape. You can see the hole distortion in the photo posted above.
The following drawings by former Team Camaro regular 'mark x22' (who sadly passed some years ago) may help set the perch angles up before welding. These are for multi-leaf but I'm not aware that the angles would be any different:

[scotty1320]

Thanks for the advice and drawings everyone.  These will come in handy.  It's nice to have this source of information available.

[Spooky]

That it the best drawing I have seen for explanation of rear end angles!!!!

Thanks for posting that up

Scott

[69Z28-RS]

That nice drawing seems to show that the pinion angle is pitched UP by 6 degrees; but I think that is wrong.  Everything I've ever read indicates the pinion statically should be pitched down by a few degrees to compensate for the opposite rotation of the differential under high torque acceleration...

Today I cut the perches off a '72 Nova rear (same as 1st gen Camaro I think), and it's pinion angle compared to the flat of the spring perches was pitched 'down' by around 5.5 degrees (measured with a digital level prior to removal).  I'm installing this rear into a '56 Nomad and I need to change the perches, but I plan to retain that initial (static) 5-6 deg downward pinion angle (relative to the spring perches).