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dbreese

Edelbrock adjustable rear upper control arms

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Picked up my control arms yesterday. Today I took measurements to determine my total working angle. Used an angle finder to get trans, driveshaft and pinion angles then did the math. Ended up with .5 degrees total working angle. I have read (many times cause I'm kinda slow with this stuff :Ds)that this is within spec. All these measurements were taken with the car's stock suspension(sans UMI LCA relocation brackets and air bags) loaded and with 1/2 tank of gas like I normally run at the track. My pinion angle is -2 degrees with 5 psi in each air bag. Then I took the air out of the left bag to 0 psi and aired the right to 18 psi. To my suprise this changed my pinion angle to -1.0. I'm guessing that when I launched with this setup my pinion angle would go to the + side ( not good).

 

With the adjustable uppers I will be able to experiment with pinion angles and maybe get a little more out of my combo with less parasitic drag.

 

I was wupped and decided not to put the arms on today tired. Might try tommorrow. I thought this was going to be easy!!!! crazylaugh

 

Might try to get too the track in the next couple of weeks for some t&t.

 

David

 

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Stock Moog rubber bushings. The Edel's came with poly's but I'm just going to keep my stocks . I know I'll have some deflection from the stock bushings but they are only about a year old. I'll factor this into the adjustment.

 

David

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David, from what I've read, on a 4-link setup, you will want between 1 and 3 degrees of pinion angle dialed in. If you have weak bushings like rubber ones, or if you have Lots of HP, you will want to be on the large side of adjustment, and if you have solid bushings, or not too much hp, you will want to be on the smaller side of the angle. I know your car runs very well as it was set up before, so you might want to keep it around the original angle.

 

What you are describing with the changing pinion angle sounds right to me. If you draw an imaginary line (from the side view of the car) along the center line of the upper control arms towards the front of the car, then draw an imaginary line along the centerline of the lower control arms forward, where those lines intersect, is the point where the rear end pivots as if it has a ladder bar setup. Hopefully that makes sense and helps helps explain your losing the pinion angle the higher the rear end of the car sits. The higher the rear of the car gets, more it diminishes the pinion angle. I'd install the adjustable uppers, pump up the right air bag to 18 psi, then adjust for 2-2.5 degrees or so since you have rubber bushings.

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My thinking exactly Scott. I didn't measure the ride height before I aired up the bag but I'm guessing it changed maybe 1" to and 1"1/2 . I was suprised it changed the angle that much, as you know 1 degree of pinion angle is big.

 

Yep that 2.0 degrees of down pinion angle at the track with 18 psi in the right airbag and 0 in the left will be my starting point. Should put me close to 0 at launch and WOT.

 

The whole working angle thing was hard for me to understand by just reading but once I got under the car and played with the angle finder and bubble level and did the math I figured it out. It's just not all about the pinion angle it's the whole drive line angle package.

 

I'll let you know how things turn out when I head to the track!

 

David

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I'll be curious to hear how it goes. I've never checked my full working angle. That may be my next project after my current exhaust project. I guess if it's off, you shim up the trans mount?

 

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I'm running stock engine/trans mounts and a the original th350 and rear. I think this was why I ended up within spec. I think when you start changing trannys from what originally came with our cars and rears, like a the Ford 9", going with aftermarket trans and engine mounts is where it becomes more critical when it comes to your working angles as all these could change them.

 

David

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That would make sense to me. I think you're going to be very impressed with the edelbrock control arms. I know I was pleasantly surprised. I tend to not like edelbrock stuff just because I don't feel like they stand behind their products, but these arms are very nice!

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They are a very nice piece. I like the fact that edel uses johnny joints instead of the a standard heim joint. No binding and they greaseable. The fact that you can adjust them on the car is a BIG plus. Did you use blue loctite on the adjusting nuts to keep them from backing off after you set them or do they stay tight?

 

David

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I've had good luck with mine staying tight, but I had a pretty good sized wrench on them! I agree with the johnny joints. They were MUCH nicer than standard ones. They will also not stress the frame mounts as much because the pivot ball is one piece and extends the full distance instead of using spacers like others.

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Ok with much work I got the arms on with the help of a good friend. crazy What a job!!! Glad it is done though. Seems that everything was in the way. Brakeline on the upper right, exhaust, which made it difficult to get a good pull with the wrenches. I ran out of time so I couldn't recheck the pinion angle but will do it tommorow. I did take it out for an easy cruise and ran it up to 70 with no vibrations. I feel I'm pretty close to where I started. I want to get the pinion set before I take it to my clandestine testing area wail on it a little. Maybe it was just me but the rear felt firmer while driving. It wasn't harsh by any means. This may be because of the johnny joints.

 

David

 

 

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I feel I'm pretty close to where I started.

 

You did lay the old ones next to the new ones to make sure they were exactly the same length before installing them right...they ship them from Edelbrock supposedly the GM factory length for a starting point.

 

Congrats on your install.

 

I have a small pinion leak on my rearend...made for a nasty install when I did mine as the oil was slung up on the arms over the years of driving... crazy

 

Bill

 

 

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Cool David. Mine were pretty easy, but I don't have exhaust up there, or a gas tank/lines to deal with lol

 

Just remember to adjust them both the same number of turns. When I did mine, I counted the number of flats I turned the center piece. Also, after you adjust the bar, I always tightened up the lock nuts, the pushed the suspension a little bit so I knew it wasn't binding and that I got a good reading from the angle finder.

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Hey Bill,

 

Yea they did match up to the stock ones and the top johnny joints were straight not cocked once I got them installed. I should be ok.

 

Scott,

 

I only wish I had no exhaust or gas tank to deal with. grin

Also got your PM.

 

Thanks again,

 

David

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Ok I rechecked my pinion angle with the arms installed. 3.5 degrees down angle at rest. With my .5 working angle that leaves me a pinion angle of 3 degrees down static with 5 psi in each airbag. With 0 psi in the left airbag and 18 psi in the right the pinion angle is reduced to 2.5 degrees down. It was 1 degree down with my original arms. I think this setup will work fine.

 

I'm heading to my home track for a bracket race next weekend so I'll let ya know how it goes.

 

I'm kinda torn as to which class I want to compete in. Sportsman is for cars 8.20 and slower (1/8 mile). I hate to slow my down but it is tough for me to compete in the pro class. I know, I know it's bracket racing and it ain't how fast ya go but how consistent ya are but when you run cars that are full on dedicated race cars I feel that I'm at a disadvantage. I like to dial my car tight based on previous runs and the weather. So racers what do ya think?

 

David

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Well this is the deal Scott. I worked all day Fri and Fri night and didn't make it home till around 1 am Sat. I was still planning on going so I picked up my buddies trailer Sat morning and brought it to the house and went to pull the ramps out. THE RIGHT RAMP WAS GONE mad. I thought I may have lost it on the way over but the locking pin was in place. My friend thinks someone stole it. He had used the trailer two weeks earlier and all was good. Sooooo the long of the short is I was tired and hacked so I didn't make it. Gonna try again this Sun so I'll let ya know.

 

David

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Man, that sucks! Sorry it didn't work out for you in that case. Sure sounds like you've been putting in the hours at work too! On a side note, I gave that info to my buddy with the 383. He thought it was very interesting how well the combo worked and is likely going a similar route, but with some different parts.

 

Best of luck with the trailor!

 

Scott

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