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Old 03-18-2010, 09:06 PM
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Pinion angle question on my '55 Belair

I'm installing a Ram Jet 350 and a T56 Magnum in my '55 Belair.

Here's a pic of the engine/tranny mock-up:



I am going to weld-in new side motor mounts and T56 crossmember. I have the engine sloping down to the rear at 4 degrees as it is supposed to be. The frame is level and the angle was measured with a digital angle finder. No problem here. I'm ready to do the welding.

Now, here is a picture of the (stock) rear axle loaded with sandbags to simulate the weight of the body. I have it loaded down to the ride height that the '55 Chevy Assembly Manual states it should be. (I re-leveled the frame after loading.)



Problem:
My angle finder says here that the pinion is .3 degrees down (negative) when i should have close to a 4 degree up (positive) reading to match the engine/tranny.

Could this be a problem with my springs or is it simply that the spring perches need to be cut and re-welded so I get 4 degrees up on the pinion???

I have no history on the axle I have so I don't know if the perches have been ever modified or not. I purchased these '55 Chevy 4 leaf springs new from JRS (John R. Springs).
I don't mind cutting and re-welding the perches if that's what it is. But if the springs could be a possibility of what's wrong, I don't want to set the perches to odd springs.

My inclination is that the spring perches have been modified but I sure can't tell from looking at the welds. The car did have rear shackle extensions on it when I got it. It is possible that a previous owner had to adjust the perches to change the pinion angle to compensate for the long shackles. I purchased and installed new stock rear shackles for it that you see in the pic.

Advice would be appreciated. I've never attempted this kind of thing before.

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Old 03-18-2010, 10:50 PM
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I could be wrong, But your springs look a tad over loaded.. I don't think the springs on a 55 is that flat with the weight on them.. I would take a look at another one just to see how flat they look.. Then I would shoot for the 4 degrees.
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Old 03-18-2010, 11:03 PM
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Quote:
Originally Posted by NEW INTERIORS
I could be wrong, But your springs look a tad over loaded.. I don't think the springs on a 55 is that flat with the weight on them.. I would take a look at another one just to see how flat they look.. Then I would shoot for the 4 degrees.
Thanks for your reply.
The '55 assembly manual states that ride height for curb weight is where the top of the axle is 5 3/4" from the bottom of the frame rail.
1955 assembly manual
This is what I have it weighted down to. It states that at design max load, the axle top to frame rail bottom is 3 5/8"

I know what you are saying about the springs looking kind of flat. However, I've also measured the angle with less weight on it and the pinion angle only changes slightly. With no weight on the frame at all, I get about 1.3 degrees up. That's closer but still shy of the 4 degrees up I should have.
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Old 03-18-2010, 11:07 PM
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Springs do look overloaded to me too. You can change the pinion angle by shimming the axle pads at the spring mount with angled shims sold just for this purpose. Leaf spring suspension needs to be set up with the pinion 3-5 degrees down compared to the trans to allow for pinion climb and axle wrap when power is applied, the more power the bigger the difference should be. In you case +1 to -1° compared to level, 3° of angle shim will get you there for a medium performance engine and street cruising.
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Old 03-18-2010, 11:21 PM
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Quote:
Originally Posted by roger1
Thanks for your reply.
The '55 assembly manual states that ride height for curb weight is where the top of the axle is 5 3/4" from the bottom of the frame rail.
1955 assembly manual
This is what I have it weighted down to. It states that at design max load, the axle top to frame rail bottom is 3 5/8"

I know what you are saying about the springs looking kind of flat. However, I've also measured the angle with less weight on it and the pinion angle only changes slightly. With no weight on the frame at all, I get about 1.3 degrees up. That's closer but still shy of the 4 degrees up I should have.

It just seemed flat to me.. But the manual should be right.. Did you consider using these..http://www.speedwaymotors.com/Angle-Shims,3354.html

You beat me to it Ericnova...


And yes if your going to be putting your foot into it, Then I would do what ericnova said.. I would set it up at the curb weight height..
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Old 03-18-2010, 11:40 PM
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Quote:
Originally Posted by ericnova72
Springs do look overloaded to me too. You can change the pinion angle by shimming the axle pads at the spring mount with angled shims sold just for this purpose. Leaf spring suspension needs to be set up with the pinion 3-5 degrees down compared to the trans to allow for pinion climb and axle wrap when power is applied, the more power the bigger the difference should be. In you case +1 to -1° compared to level, 3° of angle shim will get you there for a medium performance engine and street cruising.
Yes, they look overloaded to me too and I am confused about that. But in my previous post I gave the link to the assembly manual. There is still something that makes me think that maybe these new springs are possibly not right. Unfortunately, I don't know of any other 55-57 owners around here where I could take a look at their cars.

That's the first time I've heard numbers like that unless it was an all out drag car. Mine is going to be street only with street tires. I may step on it once in a while but I'll never take it to the drags and never put sticky tires on it.
I've heard some say 2°negative for a street car but many say 0°.
The other thing is that I will be installing is these traction bars that will virtually eliminate axle wrap.
So, I was figuring I should shoot for 0° which would be 4° up on the pinion at ride height and 4° down on the engine/tranny.

I'm not sure how you got the numbers of what you thought I needed in your last statement. Right now I have 4 degrees down on the engine and .3 degrees down on the pinion. From the numbers you give, I would be good to go now without an angle shim ( I have 4.3 degrees now which is within the 3 to 5 degree range you state). Or, am I not understanding you right?

I've seen those angled shims but have also seen pictures of broken ones. Plus, it looks pretty easy to just cut and re-weld the perches. I just want to be sure it's the right thing for me to do.
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Old 03-18-2010, 11:47 PM
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Quote:
Originally Posted by NEW INTERIORS
It just seemed flat to me.. But the manual should be right.. Did you consider using these..http://www.speedwaymotors.com/Angle-Shims,3354.html
You beat me to it Ericnova...
And yes if your going to be putting your foot into it, Then I would do what ericnova said.. I would set it up at the curb weight height..
Those shims are for 2 1/2" wide springs and mine are 2". I'm not sure if I've seen them in 2". But, anyway, I think I would rather just cut and re-weld the perches.

So, what numbers do you think I'm best shooting for considering I have those traction bars and my car will be only for the street (and a lot of highway)?
Do you agree that going for 0° degrees (4° down tranny and 4° up pinion) is best for me?
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Old 03-19-2010, 12:07 AM
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Quote:
Originally Posted by roger1
Those shims are for 2 1/2" wide springs and mine are 2". I'm not sure if I've seen them in 2". But, anyway, I think I would rather just cut and re-weld the perches.

So, what numbers do you think I'm best shooting for considering I have those traction bars and my car will be only for the street (and a lot of highway)?
Do you agree that going for 0� degrees (4� down tranny and 4� up pinion) is best for me?

With them traction bars. I would go about 2 degrees up. Or just stick with the 4 degrees up.. You should be OK either way.. And I agree about cutting the perches off ... That's what I would do... Hope this helps..


On a street cruiser 4 degrees will cancel it out..
On a car you will be kicking on. I would put it around 1 to 2 degrees up..
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Old 03-19-2010, 12:21 AM
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Quote:
Originally Posted by NEW INTERIORS
With them traction bars. I would go about 2 degrees up. Or just stick with the 4 degrees up.. You should be OK either way.. And I agree about cutting the perches off ... That's what I would do... Hope this helps..
On a street cruiser 4 degrees will cancel it out..
On a car you will be kicking on. I would put it around 1 to 2 degrees up..
Yes, that helps a lot. Thanks!
It will be a car that is mostly a cruiser. But, I might put my foot into it once in a great while just to show off. That's why I wanted the traction bars so I wouldn't be embarrassed by wheel hop. I've seen that and it's ugly.
I do wish I could find some other 55-57's to look at just to make sure in my mind that my springs are normal.
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Old 03-19-2010, 12:30 AM
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Quote:
Originally Posted by roger1
Yes, that helps a lot. Thanks!
It will be a car that is mostly a cruiser. But, I might put my foot into it once in a great while just to show off. That's why I wanted the traction bars so I wouldn't be embarrassed by wheel hop. I've seen that and it's ugly.
I do wish I could find some other 55-57's to look at just to make sure in my mind that my springs are normal.

I do know what you mean,, I haven't used them traction bars.. But heard they work very well.. My 57 chevy had 18.50's on the back, with a 320 gear, And at 45mph it would fry the tires.. You can ask wretched ratchet to check his car and see how the springs look.. He would be glad too.. But like I said I would set everything at ride height.. ( curb weight).. And I think it will all work out fine. Good luck..Randy
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Old 03-19-2010, 12:43 AM
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Thanks Randy.
I PM'd Wretched and asked him to take a look at this thread.
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Old 03-19-2010, 12:45 AM
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Quote:
Originally Posted by roger1
Thanks Randy.
I PM'd Wretched and asked him to take a look at this thread.

Anytime...
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Old 03-19-2010, 01:14 AM
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Sorry to confuse you, I missed the decimal point in your first post, I was trying to get you to arrive at 0° to +1° for pinion angle, to end up 3-4° different from the trans to allow for pinion climb and flex. You are correct you can tighten that down due to the traction bar you are using.

You want to keep a couple of degrees difference in there to promote rotation of the needles in the u-joint cups.
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Old 03-19-2010, 01:35 AM
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Springs?

Let's talk about that engine. Looks to me that it's fix'in to put a hurt on that rear suspension with 400 ft lbs of torque and a 5 speed manual. Might want to re-think those springs before you commit to the pinion angle.

Don't forget about the weight transfer when the front end rises too. That adds to the equation. Just a few "show'in off's" can also do damage. Better to be safe than sorry right?
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Old 03-19-2010, 08:56 AM
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Quote:
Originally Posted by sqzbox
Let's talk about that engine. Looks to me that it's fix'in to put a hurt on that rear suspension with 400 ft lbs of torque and a 5 speed manual. Might want to re-think those springs before you commit to the pinion angle.

Don't forget about the weight transfer when the front end rises too. That adds to the equation. Just a few "show'in off's" can also do damage. Better to be safe than sorry right?


There's no need at this point to reinventing the wheel.. I believe that the tractions bars he has will help.. No this won't be a full blown racer, But it will be a fun driver.... Setting this car up different at this point (Painted frame) I'm sure is out of the question.. Again he's looking for a crusier,, And a little kick in the paints now and then.. My 57 Chevy was built with springs and with 18.50's tires with a big block.. And ''IT WAS A VERY FUN CAR !!!!! It would sure lay down some rubber.. And yes them black marks was from that car... They were well over 150 feet.. And no power braking or water had to be added.. Like I said this was a very fun car... Good luck Mr. Roger..

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