In practice, things are different. Most really old iron had poor paintwork with little or no primer or surface preparation, resulting in the finish of iron oxide that graces most engines when found.
My Lister CD generating set is a lovely brown - rusty brown - all over. Everything on it apart from the Mawdsley dynamo is red rusty. The dynamo has most of the original paintwork on it, probably because they put a coat of primer on before shipping round the corner in Dursley to Listers.
First thing to do before anything else - take a photograph of the lump in 'as found' condition. This will act as a reference for later work and is also nice to show the original wreckage later on when it is finished.
Second thing, spray all over the exposed threads and nuts/bolts/linkages with WD40. If you buy the bulk pack, you get a free hand spray gadget and the price per litre is a lot less than the price of the aerosol ! It also lasts longer for some reason, probably because the spray is not so fine and less gets blown away on the wind. Leave for a couple of hours and spray again.
Then you can start stripping down in earnest. Get a load of decent boxes that are nice and strong and with stapled bottoms (wine merchants and off-licences are a good source)
Try and be systematic when dismantling, and take more photographs of significant stages of the process. Always put nuts and washers back on the threads they came off, and move any gaskets that you can remove in one piece to a safe storage place for future reference. Listers are pretty good to strip, especially the larger diesels. Everything is big and lumpy, and all the bolts are nice and oily (usually !) Petrol engines tend to have lots of rusty bits as the petrol washes off any oil that may be about.
Keep valve spring cotters or pins with their matching valve and cap, and make sure that pistons are marked with their orientation in the cylinder bore, either by makers marks or by your own. Anything damaged or missing needs to be noted for future repair or purchase as the case may be. Don't be a butcher and use a large hammer and screwdriver to get things off, you will regret it later as sure as day follows night ! If something won't move, it is for a reason. Pistons get rusted into bores, heads stick to gaskets, flanges and threads rust together, particularly BSP water fittings. Use your brain and not your brawn.
Try to keep dismantling down to a bare minimum, so you have less re-assembly to do later on. If the cylinder and piston look OK, and the rings are free and clean, then there is not much to do there. Use a decent ring compressor to refit the piston, making sure that it is copiously oiled before you slide it into the bore. Make sure that the alignment is correct as previously marked/noted. Valves and guides are reasonably simple to assess. If the valves are a smooth fit in the guides when pulled out by 30% of their length, then you are OK. If not, then the degree of wear will dictate how soon you need to replace the guides and/or valves. Sideways movement exceeding 2mm in total will necessitate replacing the guides.
If the valve stems are worn, then the valves themselves will need replacing. Measure valve stems just below the cotter groove or pin hole. New guides usually are sufficient to take out most of the serious slack. Note that big engines with long valves will need to have these guide figures adjusted to take into account the sizes involved. Grinding valves in shouldn't be a problem for anyone, but don't overdo it, and don't try to polish the ports and valves like a racing engine; nobody will notice once reassembled, and although there are some small benefits, your labour is better directed elsewhere.
If you are going to pull the crank etc., check the timing marks BEFORE you strip it all down. The tale of a lad who worked with me will tell you why: Steve had a Bedford diesel out of a truck and on the floor. He had shown quite a bit of initiative and got it cleaned off and had stripped it all down. Later on, he tried to refit the timing gears and line up the marks. The problem with most commercial vehicle engines such as the Bedford, is that because the gears also drive the compressor and fuel injection pump, there are rather more gears in there than usual. The second problem is that there is an idler gear between the crank and others, and this has three timing marks on it, one for the crank, one for the crankshaft and one for the fuel pump. The complete set only comes up in line once every 100+ turns, and Steve had moved the crankshaft to check something else before fitting the injection pump, and he had forgotten how many turns he had rotated the engine. Thus he had to start all over again and take out the idler gear and re-time the whole lot.
You will not have that kind of problem with most singles and twins, but it is worth remembering that timing marks are there to be used, so make sure you have made a note of their positions. If you loose the timing and cannot find the marks, you will have to find another of the same engine and check valve lift at a certain crank position and at a certain valve clearance figure. This will give you the data to do the same on your own engine. Using a crankshaft timing disk etc. is all very well, but unless you have makers data re valve timing and overlap, it is quicker to copy another engine. Note the comment about the valve clearance figure; a slack or tight tappet will alter the relative valve timing position. Watch out also on twins, for the timing is usually for the No 1 cylinder, not the No 2. Same for the injection pump spill timing marks, unless they are separately marked for No1 and No2 cylinders.
Bearing condition is very important, particularly now that stocks for the older engines are exhausted. Bearing clearances will vary according to usage and diameter, but generally allow about 0.003" to 0.005" per inch of bearing diameter. This is not a hard and fast rule, just a guide. Note that splash lubricated bearings may run with more clearance than pressure lubricated types. Any serious grooving or surface damage to plain bearings will have to be sorted out. If the basic assembly is obviously knackered, then you will have to try to get the journal ground and undersized bearings made. There are quite a few people in the supply side of the hobby who are casting new white metal bearing sets, and some will also offer machined sets. If you can get new parts, make sure of the undersize amount when you order. If the grooving is not too deep, and the bearing is not unduly slack, it is worth running the engine to see how it sounds. If the engine sounds OK and there is not obvious distress in the bearing, then I would leave it alone.
Carbs and Magnetos are a specialist subject all their own, and I will not get too involved in their repair and refurbishment here. If the carb is cleaned up, all the jets blown through with compressed air (not poked through with a piece of wire or wood) and the float and valve (if fitted) are OK, then again it is worth trying it out before deciding to replace it. You can clean off accumulated brown deposits with paint stripper, it is much quicker than most solvents. Magnetos need a bit more tender loving care (TLC) than most things, as they really make or break the project if they play up. If the mag drive shaft turns freely and without lumpiness (note that the magnets in the device will pull at the armature every revolution, don't confuse this bearing damage) and you can get a decent spark when it is flicked over, then leave it alone. If the bearings needs attention, then you really need to strip it down, and that will have to be in another article.
Cooling fans, covers etc. are fairly self-evidently OK or not. Water cooled engines will need flushing through with a decent rad flushing liquid to get out any lime scale and debris that have accumulated in the block, head and radiator/tank. Radiators from older engines are pretty robust, but the Spiral Tube Co. manufactured radiators are more of a problem, as they used cast top and bottom tanks in ali or cast iron. Corrosion in these can spell finis to a radiator. Water pumps were not very much in evident on early engines, although screen cooled engines used them for circulate the coolant. Thermo-syphon cooling was the norm, and it was also pretty reliable. Hoses and pipes are easily assessed for condition, but make sure that you clean out all of the corrosion, pin-holes can appear with startling speed once you get some hot water in there !
Flywheels and keyways will need close scrutiny, and I always remove flywheels where there is any doubt as to their condition or tightness. If all is tight and secure, leave them alone. A shot of WD40 on the shaft to flywheel joint on a regular basis will gradually work it's way into there, and make any future removal that bit easier. It will also show any impending looseness by a brown trace of rusty WD40 coming out and marking the crankshaft when running. Drive pulleys are similarly inspected, noting that pulleys are fitted with non-gripping (parallel) keys and clamping screws. Removal of the pulley is usually much easier than getting the flywheels off.
Porosity in engine castings is generally quite rare, although you can occasionally run up against a factory 'bodge' in the form of a piece of lead worked into a water jacket blowhole. Another regular is the 'reclaimed' crankshaft with a strange undersize on the bearings. Most factories reworked production engines that had minor faults that were discovered on assembly or test. My Cub generating set had to have another engine fitted, and out of three units we found one that did not have any casting faults. There was a very sneaky repair under the front of the timing case where the milling cutter had burst into a blowhole in the water jacket. They had pushed a lead plug into the hole and peened it over so it didn't leak.
We only found this one when the original block was stripped and cleaned up to see about getting some frost damage sorted out. Any serious porosity will have to be addressed before reassembly can commence, and although some surface roughness was always acceptable, large holes are not really on if the engine has been restored. The hole can normally be filled with motor body filler such as Plastic Padding or similar. Use as directed and it will make a decent repair. If the hole is in a structurally sensitive part, such as a flywheel hub, then you will have to take a look to see what effect it will have on the integrity of the engine. If the hole is original, it will probably not cause any problems, having run for forty or more years without incident. If the hole is in the wall of the crankcase for example, and is not causing a leakage of oil or coolant, then fill as above. Anything leaking will need further attention such as welding.
When starting to reassemble, make sure that you have the right gaskets and the right gasket material for all the joints. Hallite or graphited asbestos is good for heads (not so much for high compression diesels) and red asbestos or thick paper for most other joints. Note that main bearing housings on some engines such as the big Listers used paper gaskets in multiples to adjust the crankshaft end float, so be careful when reassembling these parts, and allow a minimum of 0.010" to 0.020" end float when all is bolted up tight. The joint will close up when hot, so do not leave less clearance. Too much clearance will allow the crank to slap about from side to side, and the timing gears will rattle as well.
Vaporising chambers as used on paraffin and TVO engines will need decoking (literally) and make sure that re-assembly is in the right orientation. Fuel tanks and pipes can again be assessed fairly quickly, pipe unions were soft-soldered on most engines, the Lister diesels came with brazed pipes from day one as I recall. Diesel systems generally are pretty reliable, but a complete mystery to most. There is a complete section in this book covering this subject. Petrol systems are also briefly covered in their own section, and that information is necessarily generalised, as there are so many petrol engines and carburettors that it would be impossible to cover them all.
Appendices Index Main