The Z Magnette Goes 5-Speed: A Report on the Hi-Gear Engineering Sierra Conversion

Last year my wife Ann decided she wanted a 'proper car' of her own as she was fed up with my uncomfortable and 'weird' collection of vehicles. Her words not mine! There was very little debate when she said that she would like to own a Z Varitone like the one we had when we were married in the late 1960's.

After a frustrating search looking at totally rotten cars advertised as beautiful and restored, we found a Varitone just 30 miles away that had been used every day to transport its owner to and from work. The body has all the usual rusty areas however inspection revealed that all the structural locations had been properly repaired some years earlier and had stood the test of time.We drove the car home and spent several weekends last summer enjoying our re-acquaintance with a car we had both had great affection for 'first time around'. Of special note was a fantastic weekend with many other Z's at Wooton Rivers when we discovered just what a friendly and helpful crowd the Magnette Register is! We had some anxiety prior to going to this event, as we felt sure that everyone would cast scorn on our scruffy Z. Instead we were welcomed enthusiastically by everyone and it became apparent that sensibly modifying these cars is not frowned upon on, in fact there is great enthusiasm for making changes that make a good car even better in order that it can be used even more regularly.

This open-minded and refreshing lack of snobbery set me thinking. Ann has been brought up on modern all-Synchromesh gearboxes. The lack of Synchro on first and a weak Synchro on second was not going to make it easy for her. Up to this point, all the driving of 'her car' had been done by me with her in the passenger seat.
Re-familiarising myself with the car 32 years on made me realise that the Z is very low geared compared with modern cars. Some of our longer journeys had me thinking that an overdrive from a 'B' would be of benefit. My lack of enthusiasm for this was the obvious major surgery that would be required on the tunnel.Then a few months ago I visited Sandown MG spares day and came across a small stand offering Sierra 5 speed gearbox conversations for the MGA. The stand was operated by a company called Hi-Gear Engineering and a brief chat with Director Peter Gamble soon had me thinking that this was a better solution to both the lack of Synchromesh and the low overall gearing problem.

A couple of subsequent phone calls to Peter Gamble had also put me in touch with a Magnette owner in Hull who had done this and with the information gained from him and the very helpful information from Peter, we decided to convert Ann's car. The MGA kit would need some modification and Peter kindly arranged for a new cast aluminium bell housing to be supplied but not drilled for the MGA clutch slave cylinder.We had already established that an MGA slave cylinder would be unsuitable for the Magnette as it does not provide enough clutch travel when used with a Magnette master cylinder.

The parts supplied were, an un-drilled bell housing, a machined aluminium clutch release lever pivot with fixing bolts, an MGA clutch release lever with pivot bolt, a gasket to go between the bell housing and the ford gearbox, an extended spigot bush (the same as the MGA conversion), a Ford gearbox rear mount, an MGA clutch plate and a speedo cable with a Ford gearbox end, and an MG speedo end. In addition Peter routinely supplied various nuts and bolts including a full set to mount the bell housing to the Magnette engine and the bolts to mount the bell housing to the Ford gearbox.

Peter also agreed that when I could give the dimensions, he would make a prop shaft to the correct length and supply a gear stick assembly that would position the gear stick in the correct place to appear central in the Magnette turret. These obviously could only be supplied when I supplied the information.
In speaking to the Magnette owner in Hull, he told me the problems he had encountered and these were:

1. The Ford gearbox could not go into the tunnel recess without the angling down of the engine gearbox assembly towards to rear.

2. This in turn meant that the prop shaft would not clear the crosspiece located midway along the transmission tunnel (presumably to contain the prop shaft if the front UJ ever failed). As a result he had removed the crosspiece and made up a new lower crosspiece.

3. Two other problems had resulted. One had been that the gear stick was positioned further back and this meant moving the turret back so that the hand brake fouled against its rear face. The final one was that the throttle linkage, which attaches to the bulkhead had to be modified because of the new angle with which the motor sat in the car.

Armed with this information, this is what happened!

  • We removed the original engine / gearbox as per the workshop manual. The gearbox was separated from the engine and the clutch plate taken out. The original spigot bearing was then removed from the centre of the flywheel. Theoretically this can be hydraulically pushed out by filling the bearing with grease and pushing a spare main shaft in, (which we did not have) so a hacksaw blade was used to cut through the spigot bearing after which it was easy to just hook it out.
  • The spigot-bearing hole was cleaned out and the extended spigot bearing supplied by Hi-Gear was inserted with bearing fit lock tight, (also supplied).
  • The MGA clutch plate was then reassembled on to the flywheel using a standard Magnette pressure plate.
  • Turning to the gearbox, the Ford bell housing was removed (four bolts) along with the clutch release mechanism and gasket. These were discarded. We then removed the four bolts on the front of the gearbox that hold the clutch release bearing guide sleeve. The sleeve was cut off leaving just one centimetre of sleeve protruding from the base before cleaning and refitting it to the front face of the gearbox.
  • The Sierra gearbox mounting was attached to the rear gearbox mounting point by its single bolt fixing.
  • The MGA clutch operating arm and thrust race were then fitted before trial mounting the gearbox on to the engine.
  • The clutch slave cylinder was removed from the Magnette gearbox and using an MGA push rod, was positioned on the bell housing before drilling and tapping the bell housing and mounting.

The gearbox was removed again and our attention turned to the car itself. We were keen to overcome the problems encountered by the Hull owner and so we looked carefully at the tunnel area.This is the bit you are going to hate!

Using a reasonable size hammer, we re-profiled the tunnel slightly by folding the front top edge horizontal and then flattening out the first two re-inforcing pressings on the top of the tunnel. These are transverse pressings down into the transmission tunnel and by flattening them, we created greater space above the gearbox. It sounds brutal but the change is very small and there is absolutely no way you can see this change once carpet is inserted inside the car. The result of this 'brutality' is that the gearbox (when we came to fit it) went up far enough to eliminate the throttle linkage problem, prop shaft fouling problem and we did not even have to alter the exhaust.

Before the gearbox could be mounted, it was necessary to relocate the clutch hydraulic flexible pipe by removing the original bracket from the rear bulkhead and locating it on the off side front chassis extension below the steering column. This allowed for a new 30-inch steel pipe to link the clutch slave flexible to the master cylinder. The original pipe is too short!

At this point we removed the gearbox cross member from the original Magnette gearbox. For those of you who are familiar with it, it has two ears on which the rubber blocks are mounted. We removed both these ears (one is bolted in and one is spot welded in).

The Magnette cross member was then offered up to the Ford rear gearbox mounting and using the hole left from the bolted on ear as the location for one side, the cross member was drilled on the other side to allow a second bolt to the Ford mounting. This resulted in the standard Magnette cross member now being fitted to the rear of the Ford box.

The cross member needed the front flange bending slightly to provide adequate clearance to the gearbox case.
We now refitted the engine into the car on the front mountings and let it rest on the front cross member. From underneath the car, we guided the Ford gearbox into place and bolted it on to the engine. We then carefully lifted the rear of the gearbox and to our amazement found that the four rear cross member mounting holes lined up precisely with four hexagon screws either side of the tunnel and just behind the original mounting screw holes. We unscrewed these screws, lifted the cross member in place and using some longer screws, located the cross member into the four tapped holes we found. It was not possible to raise the gearbox all the way, as the rear of the gear stick turret was too far back to appear through the original gear stick hole in the body. We noted the clearance required and cut the gear stick aperture (almost 2 inches) further back towards the handbrake.

We then raised the gearbox again until it just touched the tunnel. At this point we noted the gap between cross member and body. We then spaced the cross member down to ensure there was clearance all around the gearbox. A safe clearance was achieved with 5/8" of spacer between the rear cross member and the body.

We measured the prop shaft length required and Hi-Gear produced a new prop shaft of the correct length with a Ford front end and a Magnette rear end. We installed this in position. Even with the rear wheels hanging un-supported, the prop shaft just cleared the tunnel bridge cross piece.

We noted that the prop shaft was not central in the tunnel and centering it we would gain even more clearance.To achieve this the rear cross member was removed and the Ford mounting to cross member bolt holes were slightly elongated thus allowing the box to be moved over slightly and hence centre the prop shaft. This distance required to centre was only 1/8".As we now had reasonable clearance in the worst possible condition e.g. the wheels hanging down, we knew there was no danger of the prop shaft touching. When we measured the clearance with the wheels on the ground, there was well over half an inch. We had solved the first problem! The crosspiece had been left in place and we had good clearance.

Next we connected up the exhaust and to our surprise and pleasure, found that it fitted and sealed without any modification.

The angle by which the engine had changed was so slight that the joints could accommodate it. (Another possible problem solved).

The clutch slave was connected to the flexible and the clutch bled normally.

The throttle was connected up and we found it required no modification. (Problem solved).

We did find that the clearance between the bell housing and steering column was minute and we were unhappy that under extremes of engine movement it might touch. We easily solved this by filing the bell housing by the starter motor extension so that it exactly matched the profile of the rear engine plate and then bevelling the new profile. This is a very simple task but only if you do it before you put the engine and gearbox into the car!

Turning to the interior, we were determined that the handbrake should operate normally. We discovered that the turret could be mounted so that its rear face just cleared the rear of the gearbox and by doing so, left sufficient space for a thumb on the handbrake button even with the handbrake in the fully down position. This however presented two minor problems, the first one was that it left an aperture in front of the turret because it was now moved rearwards and secondly the Ford gear stick could not be used at it would be positioned too far to the off side and to the rear to come through to the turret centre.

A small piece of sheet metal was cut and riveted to the tunnel and solved the problem of the gap in front of the turret. A quick sketch and a fax to Hi-Gear resulted in Peter (overnight) making up a special stick that projected the Ford change forward and towards the near side by the appropriate amount. The stick now appeared through the very centre of the turret in its new position. Problems solved!

The Magnette speedo cable was removed and replaced by the one that Hi-Gear had supplied and went in without modification.

The Ford box was filled with oil and the reversing light, switch was connected to the existing loom. The time to complete all this was (in actual time) 2½ days.

What is it like to drive? No clunks, bangs or jerkyness. The gear change is, as you would expect from Ford Sierra, a delight. The synchromesh cannot be beaten, no matter how fast you try to change. The first three ratios suit the car far better than the original first and second (it was almost not worth using bottom gear on the original box). The spacing of all the gears is much better and makes the driving experience and the actual acceleration better. (You can keep the car in the power band, as the ratios are closer).

My first run seemed however disappointing. I took the car up to 40 miles per hour on the speedometer and the engine still seemed busier than I had imagined in 5th. Indeed I was expecting a big revs drop from 4th to 5th as 5th is an overdrive. It's indirect at 0.8 to 1.

It was only after I returned from the initial run feeling that I still had a gearing problem that I realised! The speedometer had not yet been re-calibrated and therefore was reading low. I had been travelling at an indicated 40 miles an hour and it did not seem particularly fast but the engine note seemed similar to 40 miles an hour in the past.

When I realised the speedo would be wrong, I asked Ann to go out in her modern sports car (MX5) and I would follow her at constant distance. She was to signal to me when she was doing a steady 30, then 40, then 50 miles an hour. This she did. When she was doing a steady 50, the Magnette was reading just 35 miles per hour.
I felt sure the car was not travelling that quickly and I disbelieved her speedometer. I therefore insisted that she went out and repeated the exercise with my own car (a Saab). Surprise, surprise, 50 miles per hour was 35 miles per hour on the Magnette. No wonder the revs where higher than I thought at the indicated 40!

I still have not re-calibrated the speedometer, but what we have achieved is an all synchromesh gearbox, much better intermediate ratios, a superb gear change and a much less busy engine when cruising.
Ann's Magnette was converted to 1622 cc before we got it, and has no trouble pulling 5th (and in fact it is still responsive).

I cannot recommend too highly the efforts of Hi-Gear and Peter Gamble in particular. The workmanship on everything he does is of a very high standard and I have been pleased to supply him with every measurement and a full set of step by step specific instructions with photos.

Peter is now prepared to produce a comprehensive kit with the correct prop shaft, gear stick and pre-drilled bell housing which will allow you (if you wish) to have the same.
Our car is still scruffy, but it now has a gear change that Ann has no difficulty with. Now where is that disc brake conversion and a servo?!!

A fellow Magnette owner Alan Slack has mirrored our conversion on a ZA (and assisted me doing ours, thanks Alan!). The only difference in his installation is the fact that there are no extra mounting holes in the body for the rear cross member. Alan had to drill and bolt through on the ZA. Otherwise the same things applied

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