Sparky's winter/spring/summer/autumn work


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Mal Clark told me that he solid bushed the crossmember, it is on my to do list.
I did think of that, but thought that all of that loading on two bolts, with no give in the bush could be too much for 45 year old metal. My thoughts were to modify the single beam mounted at each end, to make it into a cross, or at least a 'T' then it wouldn't take a lot of strength to keep it level. The beam I used was a NOS one and the bushes are possibly 40 years old, so I have bought some poly ones to replace them, and the rest of the bushes to locate the modified beam are also PU.

Should work, I'll let you know :cool:


Staff member
I've carefully folded up one of the 2mm brackets, (clamped it in a vice and beat it with a hammer), and cut out another one for the other side. I have welded the one on the top right, finished it off with a flap disc and trial fitted a PU mount - all seems to be going to plan :)


The four cut out pieces will be welded to the 40 x 20 box sections after I have taken a bite out of it to recess the rubber mount.



Staff member
I've finished the two 40 x 20 sections, and after a test fit


Painted them up, fitted the 16mm bolt supports from the old ones, plastic end caps etc, the diff bit now finished :)


Further forward, I reached under the car, and whipped this bit out.


I wanted to replace the tubes, which were welded in to take some adjustable brackets for the struts to attach to, with some longer ones, and also upgrade for extra strength the 18x2 with 20x3. I cut them off as flush as possible then ground them back with a flap disc. I still had to drill them out though, took an age :oops:

I made a mock up of the new crossmember although the tubing won't be as long as here, just done to see what it would look like.

new cross.jpg

The box section at the back (closest to you) will have hole in each end to connect to drops links from the side of the centre tunnel (under the rear seat). Try twisting with those in there :)

The front bar will be PU mounted onto the brackets attached to it, which in turn will be welded to the inside of the centre tunnel.

front bracket.jpg

I have replaced the bushes with some PU ones which are a nice tight fit, and have really tightened up the cross member. After the rear suspension was disconnected, it was actually quite easy to twist the cross member with just hand pressure :hmm:. With these new PU bushes, and the extra mounts in the tunnel, that should hold the diff in place much better.

Now poly.jpg

That's all for now, I want to go for a drive !!
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I wonder if it would be a wise move not to connect the diff to the rear trailing arms ? and use the crossmember as a guide for the tubes and let the forward bushing do the work ?

Something is telling me that the loadings from the trailing arms will be transmitted into the diff if the tubes are welded to the crossmember. As you have found the crossmember does move around very easily, but granted is made stiffer by using poly bushes.


Staff member
hmmm.... More to think about.

I was thinking that the crossmember used to control diff movement albeit in a slightly different (completely different) way. It's also a substantial piece of metal. The front mounts are only really there to help out a bit, I doubt if they would take the full force of that diff torque.

With the front mounts assisting, the new PU bushes and the drop links controlling the crossmember's tendency to twist, it should keep it all under control.

Off for a ponder .............:hmm:



Well-Known Member
Oh dear, sorry :oops:
It just seemed a bit alien to be putting the diff and suspension loadings through the crossmember.
Just supposing I was to want to stop the nose of a jag diff from going up and down under load, I think I would fit the box sections to the side of it as you have done. I would then think of sending tubes upward to the floor with a reinforced plate on the floor and poly bushes either side of the floor as per your front mount, trying to get this under the rear seat if it was possible.
Going back to that bloody Lotus. The Elan diff hangs on rubbers from the top. The bottom has a couple of lugs cast in the rear diff cover that hang down a bit either side. Rods go through these holes with a bush either side, the rods head forward 15" or so and then bolt to the chassis.
So there are three ways to do it, either go forward, or backward with supports from the bottom, or go upward from the front.
I do favour going upward. Nothing seems to be a strong as going from the diff nose area upward.

You have done all the work now, try it. All you will have left over if it does not work is two brackets welded to the tunnel, no big deal and you can re use most of the stuff if you change it later.


Staff member
So, after much pondering I have come up with this

I want to use the crossmember as I can always revert to the original set up without having cut holes in the base unit. My original thoughts were just to control the diff movement with two struts which would try to push the crossmember forwards. This didn't work too well, so I tried to toughen it up so it would take the pressure.

After much thinking, it occurs to me that the way I am doing it transfers a lot of the torque to the crossmember. If you imagine a circle with the centre being the centre of the driveshaft, the torque of the diff is trying to turn around that centre. My set up has the full torque going to a point 12cm away from the centre and pushing forward. If I can make that point of control further away, I would need less strength to control it.

So, I thought I could bolt a steel plate to the original rubber bush in the middle of the crossmember, then redesign the lower part of the cage to connect to this, so I would have a control point 72cm or so from the diff centre so only 1/6th of the pressure would be needed to control diff movement, and use the crossmember in the way it was designed, controlling upwards movement as per the original Rover diff.

If it doesn't work, I'm blaming Mark :)

All I need to do is recut the hole that I had welded up in the crossmember, then the two bolt holes, refit the rubber mount and weld up the holes where the tubes went through, and refit it......... Or just fit the spare one :cool:

I found a couple of these hefty looking brackets in the warehouse and welded a bolt through one of them to fit into the bush.


The propshaft runs over the top of this and is quite close so I filed the head down a bit to get a bit of extra clearance, then refitted the crossmember into the car. Problem is, I couldn't remove the bracket as the propshaft was now in the way. I didn't want to be in the position where I couldn't remove it without removing the rear suspension, so I tried removing the prop from the diff to see if I could get some wiggle room.

Two things :oops:

1/. There wasn't enough wiggle room to lift the whole bracket up high enough, so I have had to remove the welded in bolt and file a square hole and use a coach bolt instead. There is enough room with the prop undone to lift the bolt out :)

2/. I was underneath the rear of the prop when I took it off and all of the oil in the little void at the end of the prop and in the end of the pinion, dropped straight into my ear. It actually filled my ear!!

Berating myself for being so daft as to lie right under a bit filled with oil and cussing a bit, it took me a minutes or so to realise that there shouldn't be any oil in there :confused:

A year or so ago, when I had just finished installation, I wrote this - "Other noises are a whirring noise from the back, possibly the diff. I do wonder if it's been sitting around for some years and just needs to be driven around to quieten down (I hope it's this one), or a bearing, or even the new prop? Not sure yet but I'll find it. It's only audible with the radio off, all windows closed and above 60mph."

More pondering. Diff has a noise, albeit a very quiet one, and now it leaks...... Not only that, but the driveshafts are out, De-Dion is out, and the diff is only held in with three bolts, brake pipe and handbrake cable. Is it worthwhile actually dropping it out and getting an expert to have a look at it as it's very nearly out anyway?

I had a chat with a local diff man and he did say that driving it around would "possibly" quieten it down but as it did need a front seal and was very nearly out, it would be best to give it a good check over. Here is one of the bearings :eek:


My credit card was in tears for two weeks! and my wallet is still in therapy!

Anyhoo, diff is back, all rebuilt and set up like a proper job :)


Put the brakes back on, all dressed up, and popped it back in.

dressed up.jpg

Now I'm back to where I was when I dropped the prop off.
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Well-Known Member
I like the sound of the new lower torque arms, I think they will be strong enough to cope. You being a glue man may have to source some heavy duty stuff to put on the bolts that go in the bottom of the diff to stop them backing out.


Staff member
I have torqued up the crossmember along with the coach bolt and the bracket that I found. I had to buy a couple of long pieces of 40 x 20 box, drilled the fixing holes in the same place as the old ones, then chopped an 8mm section out of them to provide a 12 degree bend. After bolting them into place I bent them to sit at 5mm above the level of the bottom of the crossmember, then tacked them into place. I had to remove them several times, welded, ground them, replaced them and generally adjusted them to fit.

I then made up a couple of cross braces, 169mm wide, same as the diff, and after refitting the new bracketry clamped the new braces into place so they fit snugly against the front pressed bracket. I tacked it all into place, then removed it all again, welded it all up fully.

I made up a couple of short pieces of 10 x 20 box to connect the lower part of the ‘cage’ to the top of it.


Then it was just a case of removing it all again, welding it fully, refitting to check the fit, and removing it all again to paint and also fit some internal supports - I was going to need to do it up rather tight, so have fitted 16mm long tube supports around the bolt holes to stop the box section warping.

new lower.jpg

I still have the original top section so I thought I would fit the whole cage together to see what it looked like on its own,

Full cage.jpg

all seemed ok, so final fit into car, all torque up, bolts glued in ;), and ready to go.

Final fit.jpg


It does look like the new arms touch the crossmember but there is in fact a 20mm gap between them.

I need to adjust the hand brake cable, bleed the brakes, refit the de-dion and trailing arms, and then drive around with a smug grin :cool:

Can't wait to try it out :)


Well-Known Member
As everyone says to me....... now all you need to do is start producing them as a kit :cool:
It will be easy to keep tabs on the front location for movement as you have the 20mm gap to monitor and the bottom of the the torque arms look to be flush with the bottom of the crossmember.
Smokey burnout video coming ?


Staff member
I can't make them as a kit, I only found two of the hefty front brackets and I need to keep one as a spare :p

The bottom of the torque arms sit 5 mm higher than the bottom of the cross member so as you say, easy to monitor. If those torque arms lift more than 8mm, I'll know about it, as that's the clearance between the coach bolt and the prop :oops:. Although, if the diff torque does manage to lift it more than 8mm, then the prop will go up as well, as it's connected to the diff nose :)

We'll see :)


Staff member
Suspension back in


The trailing arms had a few chips on them, so I have rubbed them down, repainted then a couple of coats of stonechip. That should keep them rust free a bit longer.

Wheels on and down on some ramps, then all suspension bolts torqued up.



Just need to get him out, quick dust off and then see if it works :)



First impressions are very good, no noise from the back apart from that lovely burble from the exhaust. I've only done 12 miles and 5 of that on the motorway. Got up to 70 with no whirring noise, so very likely that was caused by the diff bearings. Everything is very smooth no clunking, no squeaks. Still got a slight road noise from the front N/S wheel but I know what's causing that.

Hopefully that's the end of the diff mods, I'll keep an eye on it obviously, but it does seem to be working just right :)


Staff member
When I first bought Sparky, the throttle linkage was rather convoluted.

1 as it was weber.jpg

The original crank bar had been turned around, then a clamp had been tack welded to the engine end of it, which pulled a cable which looped down around the top of the bellhousing, then back up, cable tied to the power steering hoses and to the carb. This had been done to operate the four barrel carb and to be honest, it worked ok. It wasn't very responsive though, the throttle pedal was a little stiff and not very "precise" so I had a think and came up with this.

2 weber done.jpg

A sort piece of box with a bronze bush inside, then a shortened uplink bar pushed an L shape lever I had cut out of a 5mm aluminium plate, and a straight bar to the carb. Much less stiff, and a lot more responsive.

When I fitted the EFI though, the throttle on the plenum was operated by pulling it from the left hand side.


I couldn't work out how to make this simple and direct, so had to modify the box section bracket a little and get it to pull on a cable, rather like the system the PO had used for the 4 barrel.

3 EFI cable.jpg

This cable went under the heater, then out forwards, up around the front of the plenum onto the inner left wing and onto the linkage set up on rear of the plenum.

4 cable run.jpg

So, back to the stiff throttle :(. It was the only way I could think of doing it though, so it had to do until I could think of a better system. It did work ok, but didn't really have the responsiveness or degree of control that a direct system has.

Quite a while ago now, I found an SD1 Vitesse with the bonnet open and noticed the plenum linkage was operated by a small cranked clamp on lever, on the back. I was sure this could be utilised with the original P6 system and somehow could be used without the cable making it neater and less complicated.

5 SD1.jpg

I had a good search through the spare parts drawer and manged to find these bits.

7 Old linkage.jpg

I thought if I replaced the top right bracket onto the steering idler and the rest onto the engine, that I would have a bar which turned when using the throttle pedal, very close to another bar which turned to operate the plenum butterfly. Sounds like a plan forming :hmm:

I found a Vitesse plenum on ebay, and sitting it on top of the Sparky's plenum shows it comes out further than the current one, and could very well line up with the P6 linkage :D I made up a cardboard clamp on lever (purple thing in picture) to test my theory and it did all seem possible.

SD1 plenum.jpg

What could possibly go wrong?


Well-Known Member
I do use a cable like your first set up, it comes from the stock kickdown link and loops over the bell housing. It never gave 100 % WOT, so recently I extended the lever to give a bit more throw, that cured that. The feel is quite good, as good as the old SU linkage. Also I suspected the secondaries were not opening so used the paperclip on the actuating rod trick, and found they were not. The link inside the capsule had fallen apart. Now with that fixed we are back to hearing that deep roar when everything comes on song.
Amazingly the performance was not down much just on primaries, but with the whole lot wide open at the top end, things happen very quickly.