Gentlemen, we can rebuild him....if we can find the parts!

Having assessed the condition of the engine and identified what was needed, and what was not, I then set about procuring the necessary parts at the right price. With a copy of 'Hemmings Motor News' to hand, I faxed everywhere in sight. Sure, virtually everything was available in Germany and in the UK through contacts in the MB Club, but the prices were high. In the end the two suppliers that gave the best quotes for parts were:

I arranged the purchase of the following principal items:

To save on delivery charges, all these items were sent to the US office of my employer and then they were progressively carried back 'over the pond' by various members of staff. The funniest outcome from this relates to the head gasket set: this was packed in a carton about 3 feet long and 1 foot square, diagonally within to prevent damage. This was obviously OK by Fed. Ex. to Tennessee from California, but rather inconvenient as hand baggage! Nevertheless, Ken did just that, without peeking inside and investigating the possibilities for consolidating the gasket into his suitcase! Again, I owe thanks to all who generously helped me in this respect.

Just whilst talking about suppliers, although I didn't purchase anything from them at this stage, the following company 'specializing in Mercedes-Benz 300 a, b, c,d sedans' were extremely helpful to me in my search for parts:.

Brooklyn Motoren Werke
Brooklyn, WI
Phone: 608-455-7441, Fax: 608-455-7442

Contacts: Michelle Brusegar & Alison Fisk

Back to the engine...the top end

Using a borrowed valve spring compression tool, I just managed to produce sufficient force to compress the double valve springs far enough to allow removal of the collets. I had a few worrying moments when the compression tool considered folding under the stress, and in one instance - 'ping' - and off across he garage went one of the aforementioned collets; an intensive search eventually located it under the degreasing vat!

The valves were then shown to the bench grinder (fitted with a wire wheel) to remove the coking: a most satisfying job, but I ended up with a face like Al Jolson! The fit of the valves into the guides looked OK, and the seats didn't look too bad either. I then set to grinding them back in: no particular problems were encountered. It became apparent at this stage that No. 6 inlet valve was unlike all the others in that it had a slightly different design of central boss. Not a problem but this set me wondering whether this odd valve was new or was it an original with the other five having been replaced.

The head was then cleaned with wire brushes, rotary and hand, until none of the grime remained - a long and protracted process, but well worth the effort: it came up like new, eventually. The mating face was then carefully cleaned up and checked for condition and flatness. The valve springs were also checked for deflection under load and found to be virtually indistinguishable from each other: not bad after some of them having been compressed in one position for 24 years! Again, attention to detail: each spring still carries its own neatly stencilled identification mark and its date of manufacture, in this case 6 November 1953.

For re-assembly, I knew that with the aforementioned compression tool I didn't stand a chance of getting sufficient leverage to fully compress the valve springs from their fully extended position. Ray made a custom-built leverage tool using aluminium angle and shelving brackets which proved super-effective. The head was then complete.

Ray operates his DIY valve spring compressor.

Bottom end

The newly honed bores were polished with fine emery cloth and, yet again, the whole lot went into the vat for a swim. The block was then painted with matt black engine lacquer along all the exposed surfaces. It was time to start real re-assembly so back onto the pallet it went, upside down. First of all I made new paper gaskets for the sump face.

Examination of the crankshaft had shown that the main bearing journals were OK as were the bearing shells. The latter were given a quick spray of anti-scuffing compound and put into place. A new rope seal went in the block at the flywheel end before the crank, still with the flywheel attached, was lowered into place, being too heavy to handle. The other halves of the main bearings were then put into place. When installed, the crank exhibited excessive end-float and so packers were made from 40 micron steel sheet and inserted behind the 'half-moon' thrust bearing. The whole lot was then torqued-up.

	Centre main bearing showing thrust bearing and packing piece.
	Torquing-up the main bearings

Pistons back in....

The USA aftermarket piston rings (Deves) were carefully fitted to the pistons without major difficulty.

Getting the pistons into the cylinders was going to be a much harder job though! The combustion chamber configuration in the W186 is pretty unconventional: the head - block interface is at an angle with respect to the axis of the cylinder bore and the cylinder block is cut away to form the combustion chamber, with the spark plug poking in from the side! What this means is that a standard ring compressor is useless as the rings have to be compressed to cross an 'assault course' profile before entering the cylinder (perhaps this is why so many piston rings were broken, insufficient care having been taken when the pistons were last re-inserted). I therefore recorded the profile of the top of the cylinder block by pressing a roll of paper around the top edge. This profile was then transferred to a piece of sheet steel that became my ring compressor when used in conjunction with a hose clip.

On compressing the rings, with a few measured blows with a rubber mallet the piston were put into the cylinders. The new bearing shells were put on the big end, and the whole lot tightened-up to the correct torque, this time with the castellated nuts on the correct way round. With a squirt of oil, the crank then turned with a satisfying 'hiss' of new rings in clean bores. Now we were getting somewhere!

....and the head back on.

With the new head gasket in place, and everything well cleaned-up, the head went back on followed by the camshaft, cam followers and chain gear.

The original timing chain had looked OK in terms of wear and stretch, but now with the timing gear assembled, I could not get TDC on the crank to match TDC on the camshaft: it was always one half tooth off either side. I therefore decided to try a new chain which, being a standard duplex ISO size, I was able to procure from a local drives and transmissions wholesaler. This solved the problem - there must have been more stretch than I could see in the original chain.

Part Four: Ancillaries