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Old 01-29-2011, 02:24 PM
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Upper A-arm positioning

I had a front suspension built for my 54 Chevy some years ago. I have restarted working on the car again recently. I can't get the engine to sit far enough down between the between the frame rails to run rams horn exhaust manifolds. I need to move the towers that support the top A-arms to the outside of the fram rails. That means I would have to shrink the A-arms and start supports from the outside of the frame rail to make room for the exhaust. The perches are pretty high and beefy. I am not sure if moving them farther to the outside of the frame and reducing the lenghth of the A-arms respectively would change the geometry negatively. I am also concerned that moving the perches would exert more twisting force on the frame and cause problems. Another concern is the stationary fastening points of the upper A arms do not allow for any adjustments. I am not sure that is good or bad? Any ideas would be appreciated.

P.S. If I were to move the perches I was thinking of putting another plate of steel under the airbag support and using the top of the air bag support to traingulate a perch support off of the top of it. Starting the vertical support using the old support s vertical wall at the outside of the frame and triangulating it on the top of the air bag support.
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Last edited by Kingpin777; 01-29-2011 at 02:36 PM.
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Old 01-29-2011, 03:22 PM
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geometry , then trig ?

You have adjustment on both the upper and lower A arms which is good, It looks like the upper and lower A arms are about the same length. also the upper is mounted flat. Equal length upper and lowers were done in the 40's on some race cars before they figured out different angles worked better. today most suspensions have shorter upper arms and the upper arms are mounted with the rear lower giving around a 5 degree angle for anti dive. when you put on the brakes the front end comes down, and the angle between the ground and the frame changes. having the 5 degree angle moves the upper ball joint back as the chassis settles under braking, giving effective castor angle , giving more stability. Jaguar xj front suspension have the upper a arms pivot shafts canated, not parallel the the center line of the car. That gives the same stability when braking , just requires more space in an engine compartment. The heidt web site has good technical information, their design is based on the Mustang II which is rated as one of the better designs. I would copy the Mustang II geometry. shortening the upper arms, mounting angles. and do a proportion ratio on arm lengths then you can get a basis for first try on setting castor, camber and toe in, For a street rod you want some thing that isn't scarry to drive, and will handle reasonably well. the 65 shelby mustang had the upper A arms mounting holes drilled one inch lower than stock to improve race handling. A good friend races a 427 Cobra.and he has done at least 2 suspension redesigns, the first one was a redesigh that the Ford engineers worked on , the bean counters said to forget the idea, the Cobra wasn't making enough money V S sales. the last one he is using seems to work. there are good videos on U tube (2009 optima street challenge cobra), He won first place and was first in all three road-autocross, go and stop competition, do you know what the spindles are from? and the steering arms to give propper akerman angle?

Last edited by timothale; 01-29-2011 at 03:29 PM.
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Old 01-29-2011, 04:05 PM
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Heidt's info

Heidt's web site has changed since the new owners have taken control, you can still find the Tech info go to their site and search for suspension 101 it's # 14 on the list

Last edited by timothale; 01-29-2011 at 04:12 PM.
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Old 01-30-2011, 11:43 PM
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Thanks Tim

Thanks for the response Timothale! I saw the Heidt's explanantion of terms and such. I stilll don't know how it is going to impact the geometry. I may try and shorten the bottom A-arm accordingly so nothing seems to change, but I am probably wrong there.

Last edited by Kingpin777; 01-30-2011 at 11:43 PM. Reason: No Title
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Old 01-31-2011, 09:30 AM
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If the rams horn manifolds don't fit I think I would look into different exhaust manifolds maybe 350 style that dump out towards the back of the motor. Like the manifolds used on a 64 to 67 Chevelle small block or some type of tube headers before I would redesign the front suspension.
Just my 2 cents, Gene
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Old 02-01-2011, 05:41 PM
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57 HalfTon

Hey Gene,

I have thought about different exhaust manifolds. First some early model truck manifolds I have. I am almost positive they won't fit. Late model headers I am not sure about because they are set up for smog. Those don't look like they will work either]. Headers are not an option for me because of the look and problems that occur sooner or later. I appreciate the input.

Leo
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Old 02-01-2011, 05:50 PM
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There are several manifolds that will fit in later model cars. They cam both eith and without AIR fittings depending on the model. It's not that hard to remove the fittings by grinding, and filling the holes for that matter. There are also SS factory headers on some of the late model cars that will work too.

If you shorten the upper arms, it will give you bump steer, and a lot of camber gain when the car bounces. It would be the last thing I would do.
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Old 02-01-2011, 06:02 PM
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Hey enjenjo

Thanks for the input on the headers. I wasn't sure if I could fill the holes or not! What if I shorten the upper A-arms an inch and the lower A-arms an inch repectively?

Thanks a lot for the input!
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Old 02-02-2011, 07:39 AM
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Kingpin, could you show us a pic of the clearance problem with the engine and exhaust manifold in place or close to being in place ?
Gene
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Old 02-02-2011, 12:21 PM
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Quote:
Originally Posted by Kingpin777
Thanks for the input on the headers. I wasn't sure if I could fill the holes or not! What if I shorten the upper A-arms an inch and the lower A-arms an inch repectively?

Thanks a lot for the input!
Shortening the A arms will get you into a situation you don't want. It's not as easy as cutting an inch from both the uppers and lowers. The lower arm is longer, so to keep the same relationship, you have to cut more from the lower arms, which moves the upper arm back in. And you will still have more camber gain than the design calls for.

This whole exercise is cutting off your toes to make a shoe that is too small fit. Move the engine so it clears the front suspension. Raise it, offset it to the right, move it back, any of these are better than cutting up the front suspension to make it fit. I have seem a 454 in one of these cars with that suspension, and stock manifolds cleared with no problem.
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Old 02-03-2011, 11:08 PM
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A-arms

A-arm to A-arm is 22 1/2 and exhaust manifold to exhaust manifold is 24 1/2. I don't want to cut up the body to make room for the transmission tunnel. I think the motor would just ride to high in the frame rails anyway. The original wheel base of the car was 50 1/2. I am thinking about moving the same configuration over an 1 1/2 on both sides keeping the lenths of everything the same? I would have to fabricate a new cross member and mounts?

Thanks to all for your suggestions and help.
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Old 02-04-2011, 07:30 AM
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what are the numbers.?

In the first photo it looks like the upper arm is higher towards the centerline of the car that would cause positive camber at bump, most suspensions today decamber at bump and have a very slight toe out on bump. With the car at ride height what is the angles of A Arms , side to side and front to back and what are the distances from ball joints, to A arm pivots measured on a grid patern to the center lines, and castor and camber at ride height, The first photo shows upper a arm higher towards car center line, if so that will cause positive camber on bump That worked on wooden spoke carriage wheels, but poor handling in a car suspension. normal suspension design today has the upper a arms shorter than the bottom Like Heidt's suspension 101 diagrams The Cobra man is an expert on suspension, was director of Ford Racing before he retired a couple of years ago. He has a lot of Info posted on the Club Cobra Site.

Last edited by timothale; 02-04-2011 at 07:38 AM.
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Old 02-06-2011, 07:23 PM
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Timothale

I am gathering the information you asked for. I had to study up on the terms to figure out what you needed to know. I got a new angle measuring tool as mine was sticking. I will have the more accurate mesurements tomorrow. I appreciate your help and patience.

Leo
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Old 02-07-2011, 10:26 PM
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Suspension Measurements

Timothale

When the car is at ride height the lower A-arms are pretty flat. The upper A-arms are at 5 degrees. Side to side or castor is about 3 degrees. Camber is 3 degrees and can be adjusted via knuckles. It is in negative camber at the moment. About and 1 1/8 inch difference between the top and bottom. The top a arms are 11 inches and the bottom A-arms are 14 inches. They are offset.


I appreciate your help in advance. Sorry it took so long to get the info.

Leo
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Old 02-14-2011, 03:35 PM
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Moving A-Arms to make room for engine!

I am lookinf to move the front end over about 1 1/2 on each side keeping everything the same. Any thoughts before I start?

Leo
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