THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

My 1966 is fitted with power steering which I presume is the later type of the Burman steering Box.
I have read that the Marles variomatic steering system was fitted from 1968.
I was wondering if the later Marles system considered better than the earlier type and what if any are the advantages/disadvantages of the Variomatic compared to the earlier type.
The reason I'm asking is that I have the chance of getting hold of a front end from a 420G which is fitted with the Variomatic.

Chris we have had many discussions on the forum about the difference between the Burman types 1 and 2 and the Adwest Marles Variomatic. If you use the search engine top right you might be able to read through some of them.
In my humble opinion if you can get the complete front subframe from a 420 then go for it. The 420 had better front brakes to start with and although I have not driven the older Burman boxes as my car has the Adwest I will stick my neck out and say the Adwest is better. Why would Jaguar change from the Burman to the Adwest and retain it for the 420 if it was not. My Adwest is very light at low speeds and my only criticism is that it is also very light at high speeds but this will be the same with the Burman.
I wrote a post on changing the seals on my Adwest here http://www.jagstyperegister.com/forum_n ... variomatic and during this process I was able to tighten up the box removing the play (which you do not appear to be able to do with the Burman) and I can report that the steering is now less vague at high speeds. Having worked on the Adwest it is or appears a lot easier to change the seals than on the Burman. The PAS pump is the same so you would not have to change anything just a straight swap of the entire subframe with brakes and hubs.

Rob

Yes, I've searched and read many posts on this and jaguarforums.com
I meant to ask whether the pump was the same.
Did I read that the variomatic uses a higher fluid pressure than the Burman?

Someone else would have to answer the PSI question although I have two pumps. My original pump which sadly stopped working and I am waiting to get it rebuilt and a pump from a 1966 S Type which is now on the car and running my system and I have not felt a difference. That might be that my old pump was not working to a high enough PSI and the old 1966 pump is working adequately.

These are values of pump pressure used by Jaguar with Hobourn Eaton roller pumps mounted to rear of generator and later stand alone Saginaw pump fitted to the 420 with Varamatic. These direct from Jaguar factory service bulletins.

S Types: 4 Steering types.

Manual
First Type Burman PAS Box with Hobourn Eaton roller pump ~ 800 - 850psi (only very early cars ~ mainly fitted to Mk2's)
Second Type Burman Box with torsion bar quill valve & Hobourn Eaton roller pump ~ 1000psi ~ fitted to most S Types (Mk2's similarly updated)
Marles Bendix Varamatic (Adwest) Box with Hobourn Eaton roller pump ~ 1000psi ~ fitted to late S Types.
Marles Bendix Varamatic (Adwest) Box fitted to 420 with Saginaw pump ~ 1200psi

Truth of the matter is all seem to work together.
Common complaint is that steering feels overboosted.
Varamatic gives best feel.
I would not fit a 1200 psi pump to a 1st type PAS Box. (apparently known for distorting their top & leaking)

Thanks Glyn I knew mine was somewhere around 1000 psi but had no idea about the others.

Thank you very much Glyn and Rob.
Do you know if the steering column is the same all the way down to the connection to the steering box for the varamatic and the Burman?

Yes the upper and lower steering columns are the same length for both boxes, 14 inch, but a different lower steering column length, slightly longer, for the non PAS steering box.