MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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NCtim
Tim Shumbera
Western North Carolina
(238 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


New Build, Rover 4.0L Steering & Firewall Mods
Posted by: NCtim
Date: October 26, 2015 07:48PM

Gentlepeople,
This was posted as a question on another thread:

I have a 1980 rust-free rolling chassis (whole car minus engine) and a rust-free 1973 driver. I want to use the CB so I don't have to do all the body mods to make it a CB and all the suspension shenanigans to lower it. Can't I just cut the firewall out of the RB, weld it into the CB and use the rack and steering column from the RB? Realizing that I have to mod the radiator area anyhow. Am I way off? Rover 4.0L engine.

Tim

Jim D. responded that I should just use the corner firewall mods. What about the steering rack? This car will also have either A/C (Nostalgic or HotRod) unit available for it.



Edited 1 time(s). Last edit at 10/26/2015 07:49PM by NCtim.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: New Build, Rover 4.0L Steering & Firewall Mods
Posted by: BlownMGB-V8
Date: October 27, 2015 11:22AM

Tim, swapping out the entire firewall is a bit extreme, can potentially compromise structural integrity, and is not really necessary. Many engines have been swapped into the CB without such extreme mods. If of course you are quite certain you are competent to do that, well it's your car. But why make one out of two?

There are four areas you need to be concerned with, plus the steering rack pinion and the crossmember:

-Passenger's side head clearance
-Driver's side head and bellhousing clearance
-Driver's side clutch mechanism
-Steering knuckle-to- header clearance

Each of these can be and are usually resolved within the limits of the CB firewall, generally as follows:

1) Look below the projection that interferes with the head on the passenger's side. Locate the vertical curved section, I think it has the plug at the top for checking the stock transmission dipstick. It is very easy to extend that curved section all the way up, which gives plenty of clearance, looks good, and has minimal impact on panel stiffness. Most people just lop off that corner, which is even easier.

2) Usually not a lot required here, but for larger engines such as the BBB and more setback often the tunnel is widened out, sometimes as far as the firewall cone. If so it means you have to fabricate a new accelerator pedal and mount. I try to avoid that. Often only the area directly below the mount needs widened, and this is just a slit, beat, and reweld operation.

3) These days, usually taken care of with a reverse external slave cylinder.

4) Now the one that scares everyone, but shouldn't, because you have options. Plan to keep the CB crossmember? Good. You can either lengthen the CB rack pinion or use the RB rack here, be aware that what you do with the rack mounts and cone will affect the required pinion length. Many ways to deal with this. If you plan to later add the electric power steering your options increase. The MGB uses only one joint in the steering shaft, a solid needle bearing u-joint, which makes road feel very positive and minimizes play. Adding joints increases play and reduces road feel. First option is to use the later, small u-joint which moves the joint up into the firewall cone. Often this is enough, but does require a longer pinion. (Note, the later RB rack has a higher numerical ratio and the pinions are not interchangeable) Pinions can be cut and rewelded using the same procedure as axle shafts. If you do that be sure the end result looks original. Some have cut out and replaced the firewall cone with the later one but in my opinion it is just as easy to cut the ends out and bend a piece of sheetmetal to replace it. Plus it gives you a custom length that is a perfect match. The only way to make the RB rack fit perfectly while using the RB cone is to use the RB crossmember as well, which then means dropped spindles to restore CB ride height.

I recommend the shaft collar conversion for the rack mounts as it makes alignment dead simple, and does not add much expense or work. It also allows dropping the rack if you should desire. Note also, if you go for the minimum here, the short u-joint and lengthened pinion, you will need to shift the bottom of the column out about 1/8" by elongating the mounting holes. Easily done with a die grinder.

HTH,
Jim


NCtim
Tim Shumbera
Western North Carolina
(238 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


Re: New Build, Rover 4.0L Steering & Firewall Mods
Posted by: NCtim
Date: October 27, 2015 04:04PM

Thaks, Jim!

Those are very easy to follow instructions. I've read all the builds here and am familiar with the firewall mods on the CB. I guess I was trying to make it easier but probably over-thought it and made it harder. I'll just use this site and the RB car as a guide to the firewall mods. I definitely don't want less feel in the steering. I've seen as many as three u-joints in the column shaft and wondered how the steering felt and if it wandered on the road. I don't want this to steer like a '65 Ford pickup.

Tim


NCtim
Tim Shumbera
Western North Carolina
(238 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


Re: New Build, Rover 4.0L Steering & Firewall Mods
Posted by: NCtim
Date: October 27, 2015 04:13PM

Hey Jim,

quote "I recommend the shaft collar conversion for the rack mounts as it makes alignment dead simple, and does not add much expense or work. It also allows dropping the rack if you should desire. Note also, if you go for the minimum here, the short u-joint and lengthened pinion, you will need to shift the bottom of the column out about 1/8" by elongating the mounting holes. Easily done with a die grinder."

Can you elaborate on this? What is a shaft collar for rack mounts, exactly?

Tim
(I forgot how to do quotes in a message)


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: New Build, Rover 4.0L Steering & Firewall Mods
Posted by: BlownMGB-V8
Date: October 27, 2015 05:01PM

If you don't mind a bit of browsing, there is info on this conversion in both the Roadmaster thread and my 340 write-up, but basically you break off the old mounts (slit then big crescent wrench on each half) and clean up, use a pair of 2 piece split collars and the saddles from 2 muffler clamps which you weld into the saddles. Trim away any excess and weld a 1/4" plate to the base for a spacer. That gets welded to the crossmember. You'll have maybe 1/4" side to side adjustment (may have to clean up the rack a bit, set the pinion close but not touching the frame rail) and it easily rotates up and down. So for alignment you simply install the rack with the clamp screws loose, spin the wheel a couple times and cinch it down. Alignment should be perfect.

This mod is exceptionally helpful if you plan to lower the rack. To be honest I really can't say exactly how well it works in the stock location because I've never actually done that. But if you do lower the rack, watch your gaiters at full lock and full spring compression. If too low the bottom A arm can slice the boot.

Jim


NCtim
Tim Shumbera
Western North Carolina
(238 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


Re: New Build, Rover 4.0L Steering & Firewall Mods
Posted by: NCtim
Date: October 28, 2015 04:46PM

Ah yes, I saw that post awhile ago and thought it looked pretty innovative.

Tim


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