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Rack and pinion theory

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Jedi Knight
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Ok guys,I need some imput from yall. I have a 76 TR7 that I am replacing the engine with a 5.0 Ford. The split sump fits nicely over the rack and pinion, but I believe the engine could go back further if I moved the rack back a bit. But before I do, I would like to know what this will do to my handling? I realize a Rover engine swap would fix this, but I already have the engine and many other parts to go with it. Any thoughts would be appreciated. Thanks
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This is kind of on topic, but, are you keeping the fresh air duct in there? If so you may not want to move it back too much or it will interfere with engine clearance. Secondly, keep in mind that rack is greasable. Don't bury it so much you can't get to it... the cars with A/C already have that problem
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I'm no expert, but I would think moving the rack might have an adverse effect on the wear of the parts.

Now the rant.... 302....
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Sorry about the 5.0 liter dude, but I thought I would try it.
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Split sump.
Can you not use a front or rear sump pan.Broncos had a rear sump.Earlier 302s had a front sump.You may have to modify the pick up.
The other comments are correct about moving the rack and altering geometry.There was a Tr around here that had a 302 and it looked real good.I never had much chance to talk to him.
I have completely redesigned the Tiger front end with some engineering help from Brian Norquist of Macyvers in Lloydminster AB.He mounted the A arms as I wasn't too sure of getting them right regarding frame clearance as the upper A arms were modified as well. I did all the rest redesigning rack mounting and tie rod angles.Works rather well.
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sunny
 
Dave,
Let me be sure I understand what you are saying. Moving the rack foward or back from it's current location might be OK, but do not move it up or down from it's current location. Did I read it right?
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thegoodbeamer,
The oil pan on a Bronco or any truck is basiclly a dual sump oil pan with the middle hump taken out. The oil pump is in the front and it needs clerance. A front sump oil pan would put the engine too far foward to work very well. I am trying very hard not to redesign the front end as my skills are not that great and my funds are MUCH less.
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I do appreciate any and all advice you or anyone else can give me. I tend to get hung up on something and can't always see what is obvious to everyone else.
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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by mailbox:
Dave,
Let me be sure I understand what you are saying. Moving the rack foward or back from it's current location might be OK, but do not move it up or down from it's current location. Did I read it right?
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<hr></blockquote>
Yes, you read it right.

Bump steer is actually toe in or out changes with vertical wheel travel. Visualize the suspension being at mid travel & the rack in perfect vertical alignment with the steering arms. (Tie rods parallel to the ground). As the wheel travels up or down, the effective tie rod length gets shorter & causes the wheels to toe in or out from where it would be at the mid travel position. Toe in if the rack is in front of the wheel centers.

Most steering systems are a compromise to minimize the toe changes with wheel travel, but there is still a slight amount. Of course uneven suspension positions such as cornering, will cause one side to change toe more than the other & steering may be erratic. Heavy anti sway bars help minimize this change by keeping both sides more nearly the same.

Since the suspension only allows the wheels to travel vertically, moving the rack fore & aft does not affect this toe change (effective tie rod length) very much, as long as the rod lengths are changed to keep the desired static toe setting. Quite a few cars have the rack fore or aft of the steering arm connection centerlines & work well.

If you have radically changed the suspension height you might need to move the rack up or down to match.

If anyone disagrees with this, I could be wrong, so please jump in.
D

[ 03-27-2004: Message edited by: Dave Russell ]</p>
 
Dave, you explained it clearly and correctly. Ride height changes directly affect bump steer, which is why, on the Spridget, after lowering the car to a racing ride height,(Effectively raising the wheel center in relation to the rack), the rack needs to be raised to compensate for the change. There are other methods, such as bending the steering arms, but moving the rack up is the easiest in this case.
Jeff
 
Hello Mailbox,
racks are not something you can relocate easily, as the steering geometry will be affected. I would be very careful about such a modification.


Alec
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Hello all,
I do not know for certain, but my feeling is if it is moved aft by any significant amount, the angle of turn will be different from standard.
I suggest you draw up a geometrically accurate plan and plot the wheel angles for standard and the proposed modification.

good luck.

Alec
 
Alec is correct.
To be specific, if the rack is not vertically in line with the steering arm pivots, there will be undesirable "bump steer". This means that the car will try to self steer to one side or the other every time a front wheel hits a bump or dip.

If you can move things fore & aft without changing the vertical position of the rack, it might work.
D

[ 03-27-2004: Message edited by: Dave Russell ]</p>
 
Moving the rack forward means longer tie rods that must be bent as in the Tiger.This in the Tiger created the ackerman problems.This is not bad for most driving but does create the plowing effect on increase turn radius.You cannot push the car with the wheels cranked.My 65 Tiger is stock and it is OK with me.The rack is well forward of center.
good luck on your project
 
Mailbox
I may have mixed up the oil pans.I do Know there was some that at that time I did mine I would have been able to do what I intended but chose another way of doing my project.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by piman:
I do not know for certain, but my feeling is if it is moved aft by any significant amount, the angle of turn will be different from standard.
Alec<hr></blockquote>
Very true. The so called Ackerman center will be moved if the rack is moved either fore or aft. Since the "proper" or "standard" Ackerman center location varies greatly with different car designs & often cannot be agreed on by various car builders, a change is not likely to be noticed very much.

The Ackerman effect which causes toe out on turns with the inside wheel assuming a different angle than the outside wheel, causes a lot of tire scuffing at garage rolling speeds but under dynamic conditions has less impact on car handling. The subject is just too complex to predict in general terms what the result of moving the rack will be. Experience seems to show that it is not a great problem.
D
 
Wouldn't it be cheaper and?safer to tune the original 6 -a strong engine which can go to 150hp+- I even have 3 Weber 45 DCOes to sell you. The TR6 front end is fairly simple so why change it? Anyway is the suspension/chassis up to it?
Hotdoc
 
would a dry sump system alleviate the clearance problem?
 
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