Friday, April 30, 2010


It is taken as read that you have had the pistons, piston rings and cylinders examined for damage, measured for wear or to ensure they have not become oval, and perhaps the pistons weighed by an automotive engineer and everything machined or renewed as appropriate.
Fit new cylinder gaskets to the crankcase halves. You can fit the pistons alone and the cylinders afterwards, or the pistons with the cylinders already attached as long as the gudgeon pin hole is clearly visible. Lubricate each bore with a little engine oil, then use a ring compressor to fit the pistons into their respective cylinders. Offer the pistons into position on the small ends – ensuring that the arrows stamped into the crown face the flywheel – then gently press home the gudgeon pins and fit the circlips. Use oil to lubricate the cylinder seals before pushing the cylinders fully home.
Cylinder head refit
Pull the push rod tubes to stretch them to a fraction over seven inches, and fit new sealing rings. Slide the cylinder head onto the studs and position the push rod tubes (seam upwards) before pushing the cylinder head fully home. Check that the push rod tubes are correctly located, and torque the cylinder head nuts in the correct progressive sequence. Fit the pushrods then the valve gear.

The cylinder head is the one part of the engine which commonly requires attention that is within the abilities of most DIY enthusiasts. Although it is still recommended that an automotive engineer inspect them in the course of a full restoration, normal mechanical repairs are another matter, and are covered here.
Clean all carbon from the cylinder head, using the correct tool and not an old screwdriver, the sharp edges of which are guaranteed to dig into the head, causing damage. Proprietary cleaning fluids such as Autoline Gasket Remover can help remove stubborn carbon deposits.
Examine the head for cracks between the valve seats or a valve seat and the spark plug hole. Check for signs of exhaust seat/valve burning. If any cracks are found then the author recommends the parts be taken to an automotive engineer or replaced/exchanged. if everything seems in order, it is worth lapping in the valves.
Uneven wear in the valve seats can result in poor sealing qualities and, if the damage is not too bad, the valves may be lapped in. It is worth while doing this as a matter of course whenever the heads have to be removed. You need grinding paste and a tool which is no more than a wooden stick with a sucker on the end — both are widely available and cost very little. Simply, the valve is placed in its guide, its mating edge is coated with grinding paste (coarse first, followed by fine), the rubber sucker attached to the valve and rotated to and fro between the hands. Every few seconds, stop, lift and turn the valve through 60 degrees and start again. inspect the valve and its seat periodically, and when you can see an unbroken matt line around both switch to the fine paste and repeat the process. When the valve and seat are perfect, the valve will bounce when dropped into its seat from a height of perhaps two inches.
Check for excess wear in the valve stems/guides by inserting a valve into its stem from the outside of the head and feeling for sideways movement. If this is found then new valve guides and valves should be fitted; although this can be undertaken at home it is recommended that the work is entrusted to an experienced professional.

Rebuild continued
Replace the fuel pump push rod assembly and the pump. and refit the distributor drive shaft: when fitting the thrust washers, use grease to hold them together and fit them with a thin length of rod to ensure that they don't drop down into the crankcase! Note the attitude of the drive shaft slot in the illustration.
Refit the oil pressure relief valve (two on cars after 1969) and the oil strainer and its cover plate. Check the flywheel ring gear teeth for damage, replace the gasket and offer the flywheel into position, remembering to line up the dowel and hole which you marked when stripping the assembly. Refit the crankshaft pulley and the flywheel. torquing the former to 33 ft lbs and the latter to 253 ft lbs — OK, let's be honest— we DIY'ers don't usually possess a torque wrench which goes quite as high as that! The sensible solution is to take the engine to a garage for final tightening of the flywheel nut—most people use a long lever on the end of their 36 mm hexagonal socket — the former is recommended.
Replace the heat exchangers and exhaust system, then the generator pedestal, inlet manifold and carburettor, oil cooler and finally the generator and fan shroud.
You can test run the engine on the floor if desired and if you can obtain an early transaxle half casing complete with starter motor. However, few enthusiasts will possess this, and so they have to refit the engine and hope for the best!

Popular Posts