Sandstone Heritage Trust - News

HTN 127 - Marshall MP6, ser no 6740184 & other projects at LionsRiver – by Chris Wilson.

23rd August 2006

Marshall MP6, ser no 6740184.

The Marshall MP6 was Marshall’s last wheeled tractor, at least until the acquisition of Leyland’s tractor business in the 80’s. After the demise of the MP6 Marshalls concentrated on Track Marshall crawlers. This plus the very low production figure of 197 makes the MP6 extremely collectable.

By the early 50’s the well accepted & reliable single cylinder Field Marshall had become an obsolete design and was due for replacement.

Marshalls decided on a big (for the day) replacement, and the MP6 was conceived. It was primarily designed to take on the increasingly high horse power American tractors in Marshall’s traditional export markets (the “P” stood for Prairie); and to replace the Field Marshall in it’s domestic role as a Threshing Contractor’s machine.

Unfortunately it succeeded in neither. Combines were making threshing drums obsolete, electricity rendered most belt work a thing of the past, and it was some three times more expensive than the average tractor on the British market. Overseas the absence of a 3pt lift made it virtually a non starter. Times had moved on and Marshalls had not read the market correctly. As a result only 197 were built over a 6 yr period.
Records show 8 were shipped to South Africa. Of these 2 are known to have survived, 184 and another restored example.
Below is an example of a superbly restored MP6, not unlike Sandstone's model
Both of these were found in industrial yellow paint and had massive industrial hitches.

6740184 has large industrial rear tyres, and it is known that it was sold originally to the Transvaal Roads Dept, where it probably pulled a grid or sheepsfoot roller.

A farmer from the Bethal area purchased it on a dispersal auction and used it for heavy cultivation, finally laying it aside some time in the 80’s due to a lack of hydraulics.

Discovered by Sandstone in 1996 it was first moved to Bloemfontein & the engine removed.
An unfortunate chain of events saw the engine totally stripped, parts mixed with another similar engine, and some crucial parts lost.

Eventually everything was moved to Chris Wilson at LionsRiver for restoration.
The challenge!

The engine fitted to the MP6 was the Leyland 350, a common truck engine in it’s day. However many parts differed ; Marshalls fitted their own high capacity aluminum sump & oil cooler and the exhaust manifold was designed for the upright outlet.

The original engine and a Leyland 370 – similar but with with a larger bore (and built to a lorry spec) had been stripped simultaneously, and the parts had become mixed up.
The photo shows all the small parts after sorting- a laborious process of reference & comparisons.

Despite the popularity of the engine in it’s day, new parts & other engines in anything remotely like a usable condition proved impossible to find.

Truck scrapyards yielded vital parts such as the correct inlet manifold for a pneumaticly governed injector pump and pully damper, while Crawfords in the UK have supplied a re-built injector pump; and many other parts are coming from them.
Ads were placed for a complete engine in the UK, but follow up investigations were not re-assuring.
Preparing the Crankshaft:

The crank was well within wear specs but required a professional polish. Leyland employed an unusual method of combating engine oil sludge formation.

The oils of the day were vastly inferior to todays, and quickly broke down under use forming a thick carbon sludge – resulting in severe engine failure.

The Leyland 350 has hollow big end journals with a through bolt holding 2 plugs in position.
Presumably the centrifugal force would force the heavier carbon deposits into these cavities where they would be trapped and kept away from the circulating oil – hence the term sludge traps.

The ones on our crank were full of a very thick black goo some of which had hardened and had to be chiseled out.
Assembly begins. Of the 2 engines one had suffered a bad lube failure, running bearings.

However the original crankshaft & block were in salvageable condition.

After extensive cleaning the block cylinder liners are honed, and the re-conditioned crankshaft placed in position using new bearing shells.
Assembly well under way.
With the crank in place the next job was to fit the pistons. The original pistons & con rods had gone missing, but a set in good condition had been obtained.
Rings were manufactured specially by Cords in Durban – unfortunately no longer in existence.
The 370 pistons were unusable and the conrods differed by not having an oil spray jet for piston cooling.
New bearing shells are fitted and the big end tensions set.
The Camshaft and bushes were in good shape. The best timing gears were selected and fitted, and the timing set. The oil pump needed little attention besides cleaning, but illustrates how tricky mixing & matching parts can be.

The 370 obviously had a shallower sump than the MP6 version, and correspondingly the cast iron suction neck which also forms the base plate of the sump is shorter.
The difference was spotted by putting the parts side by side and the correct one fitted. Failure to observe this could have been disastrous.

Finally the timing cover was fitted with a new seal and the pulley with the all important damper fitted.
At the rear Leyland employed a rope seal.

Woven rope of the correct thickness was obtained and carefully cut to length. The adaptor plate which is a Marshall part, not Leyland was then bolted into place.
Clutch & pulley drive housing.

The clutch is a Borg & Beck, probably a standard lorry unit of the day. The flywheel has been skimmed as has the pressure face plate, and the drive plate re-lined. New springs have been fitted to the pressure plate.

A new release bearing was obtained, but on fitting it was found that there was excessive play between the carrier & the tube, an unusual occourence resulting in serious mis-alignment. Examination revealed that a nylon bush had melted – it is assumed the release bearing began seizing and overheated. This has been re-bushed.
The flywheel has been fitted with a new pilot bearing, and finally the clutch put together & lined up.

The clutch housing is also the transfer box for the pulley – which 6740184 appeared never to have had.
Strangely a bevel gear and engagement collar are in place – unused.

Besides a lot of dirt the unit was in good shape.
Subsequently the housing has been fitted to the engine and the whole sub-assembly turned right way up.

The next phase will involve fitting the engine to the chassis, thereafter other components such as the cylinder head and pump – already re-conditioned – can be fitted.
Engine mountings.
The MP6 has a strange mounting arrangement. Instead of forming a part of the chassis, being bolted directly, or being cushioned by rubber mountings Marshall secured the engine by 3 metal to metal pins & bushes. Obviously over the years the engine torque produced movement as there was considerable wear on these. Shown is the front mounting & one of the rear, after re-building.
Other Sandstone projects @ LionsRiver.
Allis Chalmers B

This steel wheeled American built tractor is in for a re-furbishment rather than a restoration. It requires attention to the cooling system, magneto, carb amongst other things.

However as always when dealing with 50yr old plus machinery the unexpected occours.

The water pump has been found to be leaking and has had to be removed & sent off for repair.
Also while changing the oil filter it was noted that the pewter mounting base was cracked through and had been “temporarily” fixed. This will have to receive attention.
Fordson Super Major Tug.

After stripping to quote, an order has been recently received to continue with this project.

Subsequent to this photo a thorough cleaning & sandpapering has taken place, with rust spots being treated with etch red oxide. A number of parts have been ordered from overseas.
Current projects at Sandstone.
Ferguson TED
No tractor collecection would be complete without an example of Harry Ferguson’s brainchild, the TE20or “Vaaljapie”. Sandstone was fortunate to aquire one recently in a very clean original condition.
Following a service & clean up it started & ran well, but has absolutely no brakes. This has safety implications and the brakes were stripped to reveal serious oil contamination.
The cause of this is seal failure allowing transmission oil to leak out.
Unfortunately thistractor is an early version which is prone to this failure, and is also extremely difficult to repair as the seal sits inside a collar which virtually has to be destroyed in the removal process.
Ferguson expert Dennis Field has been contacted. He offers an update kit which can be fitted easily and is much more effective.

A quote has been submitted and an order is awaited.
Fordson Super Major
A beautifully original example of a classic. Whilst a best seller in it’s day few remain in the country as most were re-exported as used units due to their popularity elsewhere.

The earlier but similar Major generally did not have live PTO & hydraulics, so was not so sought after.

This tractor originating from Frere has been thoroughly serviced and has had it’s starter & other electrical components overhauled and is now a good runner again, although worn rings make a midwinter cold start difficult.

Some electrical parts outstanding, eg solenoid, quote submitted awaiting order.