Thread: 48 Plymouth rack & pinoin

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I am looking for some advice.

I have a 48 Plymouth 2 door sedan that I want to install a rack & pinion steering. The car has been modified with a Desoto hemi and unfortunately the prior owner(s) did not do a very good job at making it fit. Some of the inner frame had been cut for the steering box that was in it. I have relocated the motor with proper mounts and have repaired the frame where the steering box used to be (it now resides on the shop floor).

I have a rack and pinion from a 86 Dodge 600 laying around in my shop. I am thinking of installing it, but I am worried about bumpsteer and other associated problems. From what I have read online, I need to have the tie rods parallel (horizontally and vertically)with the lower A arms. Also, the inner tie rods should be at the pivot for the lower A arms. The A arm pivot to A arm pivot measures 14" and the rack inner tie rod to inner tie rod is 25". I want to keep the stock front suspension on the car (maybe later install either lowered spindles or airbags for a better stance).

Does anyone have any thoughts where I should mount the rack & pinion? It will be on the engine side of the k frame, but is there any specific place I need to have it located (for tie rod angle consideration).

Thanks,
Andy

First you'll need the weight of the car, total and front to rear, to be the same as when it is all together. The tie rods should be parallel to the floor with the car resting at it's normal ride height.... Then to check, you should use a bump steer fixture and dial indicators to check the bump steer.

Dave,

Should the tie rods be parallel with the lower A arms? Or perpendicular to the frame rails? The attached sketch I made is a top view of what I am trying to ask.

What is an allowable amount of bumpsteer? You mention dial indicators, does it get that percise?

Andy

I'd make the tie rods perpindicular to the rails... running them parallel with the A-Arms and the arms at that much of an angle would put a lot of stress on the rack and probably lead to some "interesting" steering issues.

Andy, something else you may want to look at is Fatman's Fabrications has a rack and pinion system pre-engineered for this car using a Cavalier rack and brackets you buy from them.

Andy, I'll give you my very best shot.
You will never cobble up an operating system yourself without a considerable amount of studying on the subject. Been there, done that.
If you want to do it yourself, buy and read these three books by Carroll Smith. This guy is the guru in my opinion, having been the crew chief for Ford Motor Company when they went to LeMan and beat the Ferraris. I couldn't make heads or tales of suspension and steering until I absorbed his writings.
http://www.amazon.com/Prepare-Win-Ca...0975296&sr=1-6
http://www.amazon.com/Engineer-Motor...0975296&sr=1-3
http://www.amazon.com/Tune-Win-scien...0975296&sr=1-1
There is nothing wrong with buying used books to save a few sheckels either, I do it all the time.

Like I said, if you want to do it yourself, absorb Smith. If you want to install something that will work the first time and don't want to learn how to do it, then take falconvan's advice and purchase a kit that has been engineered to work properly from the git-go. The chances of you cobbling up a system that will work properly without the knowledge gained from an expert is probably somewhere in the 10,000 to 1 range.

Thanks to everyone giving me some much valued advice. As winter sets in and the garage concrete is unbearably cold; too cold to lay on it for long periods of time. I think it is worth using Fatmans system for the steering. I found the brackets on Fatman's web page for $225. A small price to pay for sanity.

You got that right, Andy. My first go around looked great after a lot of work but ended up in the trash after I had a suspension guy look at it. Lots of time down the drain, wish I had done it right the first time.