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Engine Swap


Bill Davies

Again going to the Treffen had me thinking …Old git at the Back …none of it, I have a tow bar so was designated recovery in the event of a catastrophe. The other reason was my engine was a 2CV 602cc unit and I was competing against the might of MotoGuzzi and BMW, and I kept up but at times of overtaking I needed a run to get speed up and an overtaking distance of nearly half a mile when encountering an artic lorry. These German drivers go like the clappers when they are being challenged, and my “pals” were off up the road like scalded cats. I had a lot of catching up to do.

So I hatched a plot to convert to a bigger power house and initially proposed to fit a BMW probably a 1000cc. I have a friend who has accumulated a number of bikes and engines so he was going to solve my problem …I thought …no chance. He had plenty of bits and bobs and I could have built up an engine but that takes time etc etc. Then an engine came up on the forum, a Moto Guzzi 1100cc complete with carbs and at a reasonable price. A phone call secured the unit and I duly went south to collect it …took the camper and the dog (he knows nothing about engines but adds to the company).

Got the unit back home and then sorted out filters and gaskets to allow a full inspection prior to inserting into the car.

Now before fitting an engine you need to make a conversion plate to mount the engine/gearbox, and and adaptor for the flywheel to allow the use of the 2CV unit and clutch mechanism. I had a word with Dave P and he sent up a sketch of what he had done and what Phil now sells …so I believe. Being Scots I am not averse to spending money but I enjoy the chase, so decided to manufacture my own.

Another lump of steel was bought and again I set off for a day at my pals to use the big lathe. I started to machine the plate to get the basic dimensions set up …then I got to thinking that there could be an easier way …manufacture a boss and bore the 2CV flywheel to suit and bolt the two together. Welding is not an option as the flywheel was a cast steel and welding is not practical, although we could have tried brazing but concluded that the heat could have distorted the assembly.

I bored the flywheel to 52mm, at which point the original fixing holes have been removed. On the inside face I extended the flat to 78mm to give a flat face for the cap screws to sit against. Then I started to machine a boss to give an overall depth of 63.2mm, this is some 48.2mm long and 76.2mm diameter(it's an piece of 3” bar that my friend had). A shoulder was formed at one end 10mm deep and 52mm dia , to slip into the flywheel.

The boss is bored 6 holes at 8.1mm dia on a 38mm PCD, these holes are counterbored 13mm dia for a depth of 30mm, this to allow the cap screws to be hidden down the holes. The flywheel was drilled 6 holes at 8.1mm dia on a 65mm PCD and the boss drilled and tapped 6 holes at M8 by 30mm deep on a 65mm PCD. This positions the flywheel in the correct relationship to the gearbox and allows the original clutch to be utillised. The two sets of holes are set 30degree apart to maximize the boss material.

The boss is then bored to suit the gearbox input shaft bearing at one end and to suit the crankshaft boss at the other end.

An adaptor plate was then marked out …the drawing on the forum shows the centres for the 2CV gearbox and I had to measure the position of the engine bolts by using a surface table and a height vernier. This was transferred onto a CAD drawing and then a sample was cut using the various dimensions. The 2CV positions were good but the engine was out …a second set of measurements was taken and another trial piece made. This was repeated using a sheet of 2mm aluminium and again the positions were good.

A sheet of 5mm steel plate was acquired and then marked out, taking care as this is the final piece, all holes were scribed onto the plate and duly popped, including the centre of the axis engine/gearbox. A circle 220mm was scribed and popped at 20mm centres to keep the mark as engineers blue gets worn off. Another circle was scribed at 215mm and this was marked and popped at 5mm centres …then the drilling started 2mm in all holes and the opened out to 5mm on alternating holes , then the other ones were drilled carefully , taking care not to cause breakthrough into the adjacent hole and thus breaking the drill. Job done and only the original drills used, no breakages. Then the plate was set in the vice and the stitch drilling joined up with a fine file and Pad handled hacksaw blade till the centre plate fell out …about four hours drilling and sawing then filing to the 220mm mark.

Then the drilling for the engine and gearbox hole was done, slightly out of step some may say, but my 8.1mm drill was at a friends who was drilling the boss …he has a big rotating table in the works drilling machine!!!, and the job is planned for the "night shift" and requires planning etc to ensure the foreman is at the other end of the shop. Job done for a bottle of Malt - good job and price.

All the assembly is by Allen screws at 12,9 so are suitable for the loading expected during use, as a precaution a dab of locktite is applied to each screw on assembly.

The bits are now all machined and a trial fitting has taken place, now stripped it is on with the painting of the adaptor plate …Zinc Primer …a reasonable match to Aluminium casting.

While it is nominally ready for installation, I will wait until the MOT is done and probably after the Montlhery trip …do not want any problems on route. It sound easy!!! …I still have to sort out the carbs, the fuel supply, the exhaust and the wiring … and a few days out with Tom around the country.

Along the way I created AutoCAD drawings of the parts if anyone wants a copy please feel free to contact me, either for paper copies or a CAD file. These will need to be checked out so if you want them , there will be a short delay.

Fast forward to November 2016… the installation was delayed by events during the year, domestics etc and the 23rdDreiradTreffen( I was co-host so had to have a reliable trike) and our closing week-ends. The engine is now in the car and I have repainted the parts welded etc and now it is on with the electrics, ignition, fuel, exhaust etc etc, so will be ready soon!!! I will keep the forum updated of progress.

Regards Bill D

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