Leaf Spring Perch Installation: - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 12 (permalink) Old 09-17-2009, 08:13 PM Thread Starter
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Leaf Spring Perch Installation:

There are far too many old wives tales, myths and just plain false information when it comes to leaf spring perches and their proper installation. I am going to show the proper installation and the proper Ford factory pinion angle on any leaf spring equipped Ford with an engine that produces up to about 400 horsepower. After that amount of horsepower, the resulting pinion angle will be less that the one I show. The pinion angle that I show is the same for any Falcon/Comet, Ranchero, Fairlane, Mustang, Maverick, Torino, Granada etc. The leaf spring perch center to center distance will change depending on which car you have. I have worked on hundreds of Ford 8" and 9" rear end housings, and I have measured the pinion angle on dozens of them to arrive at the angle that I set up housings with.

While you can weld them in the car with everything clamped in place, I use a far simpler method that allows me to install the perches on a bare housing on a bench. I use a simple "C" channel jig to install leaf spring perches. The channel has a pair of 18" long x 3/8" wide slots milled in it to allow leaf spring perches to be installed at any center to center distance. In order for the bottom of the rear end housing to clear the jig, I use a couple of 2" x 4" steel blocks for the leaf spring perches to sit on. The steel blocks have an allen head bolt that the spring perch loctaes on, and a stud on the bottom that will bolt the the jig.

With the steel blocks set at the 42 3/4" center to center Mustang/Falcon spring perch distance, the housing is set on top of the pads. A measurement is taken from the edge of the spring perch on each side to the edge of the housing, and adjusted until the measurement is exactly the same on both sides of the housing:

The spring perch jig is sitting exactly level on the bench that it is clamped to. A magnetic angle finder is placed on the centersection mounting surface, and the housing is rotated up until the angle finder reads 5 degrees up. 5 degrees up is the Ford factory angle measured with the spring perches perfectly level. The pinion angle will change once the housing is bolted in the car, but this is the method and angle to use when welding them on using a jig on a bench:

Measure twice, weld once!!!! Go back and double check the side to side measurements and the pinion angle a couple of more times. With everything where it needs to be, tack weld the perches in four places:

I now weld the perches halfway on one side of the perch to prevent warping of the housing tube. I flip the housing over and weld halfway on the opposite perch. I continue to alternate welding the perches from side to side until they are both completely welded:

The housing is now ready to be bolted in the car:

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Last edited by FATNFAST; 04-02-2016 at 10:43 AM.
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post #2 of 12 (permalink) Old 09-19-2009, 09:41 AM
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Re: Leaf Spring Perch Installation:

Nice Job F15... and nice welding too by the way!


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post #3 of 12 (permalink) Old 09-23-2009, 02:05 PM
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Re: Leaf Spring Perch Installation:

A++++++ Just what the doctor ordered , thanks for some very useful tech
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post #4 of 12 (permalink) Old 09-28-2009, 04:36 PM
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Re: Leaf Spring Perch Installation:

Excellent welding, and I see you used the KISS method of fabrication. KISS= keep is simple
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post #5 of 12 (permalink) Old 03-22-2010, 06:44 AM
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Smile Re: Leaf Spring Perch Installation:

Very nice welds. Hey are the falcon/mustang perches in the same spot ?center to center ?

Thanks alot
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post #6 of 12 (permalink) Old 04-29-2010, 10:55 PM
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Re: Leaf Spring Perch Installation:

Wow, sometimes the internet works great. This was the first link I tried and the info is bang on. Thanks F15, I don't have a rearend with perches on it and hope to build my rearend soon and wanted to know the stock angle. Thanks again, great article.

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post #7 of 12 (permalink) Old 04-30-2010, 06:44 AM
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Re: Leaf Spring Perch Installation:

I still hate you for all of the EXCELLENT beads you are able to lay down!

I'm going to try and get that good this year with my Miller and some sticks... I can't afford a mig with that capacity so I gotta stay old school.
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post #8 of 12 (permalink) Old 10-14-2012, 05:35 PM
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Re: Leaf Spring Perch Installation:

FE .....if you have only a stick welder, I have a rod that will make the same quality welds. 70 thousand #'s per sq.inch strength. Try locating an 8'th" 7024 rod. Now it;s a flat weld only rod, so you have to have your project flat or up for the welding process. Try about 110 amps for heat and keep the rod pointed at a 45 degree angle to the spring perch. Beautiful strong welds and you don't need a mig outfit to do it.This rod uses a heavy iron flux so you need to run her a little hot. We use to call them "Jet Rods" because of the speed of metal perduction.
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post #9 of 12 (permalink) Old 04-02-2016, 08:09 AM
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Re: Leaf Spring Perch Installation:

This is an old article, and the pictures are currently missing, but I followed the instructions, and my pinion angle turned out perfect! Great writeup!

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post #10 of 12 (permalink) Old 04-03-2016, 02:01 AM
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Re: Leaf Spring Perch Installation:

??? Pics still show ok for me
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post #11 of 12 (permalink) Old 04-03-2016, 03:25 AM
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Re: Leaf Spring Perch Installation:

I see all the pics here too . . . .


65' Stang Street/Strip. Dart 434W NA, Victor heads, G101A 4 Spd, 4:56 rear gear, on 93 octane pushing 3550lbs. [email protected]
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post #12 of 12 (permalink) Old 04-03-2016, 08:21 AM
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Re: Leaf Spring Perch Installation:

I added them yesterday. Images were lost in merger. Some images I had backed up. Other pics maybe long gone unless member might still have images.

Rick DeVito in Indy "Blue Thunder 408W" [email protected] mph 1.27 60ft Rod & Custom MII Sales
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