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When it comes to under the bonnet matters, you need go as well as show

There’s no point having a lovely classic that doesn’t go like it should! So spend appropriate time and money on making the engine perform as good as new – or why not even better?

Some prefer to test run the engine, or at least carry out a compression test before deciding on the next course of action, and this is good thinking because if the unit is sound in wind and limb, you may be opening up a can of worms by stripping a perfectly good engine which either doesn’t need overhauling, or is difficult and costly to fettle.

• If you do intend to strip the unit for whatever reason, it’s folly to put it back together without replacing easy to renew and low cost items like the main bearings, shells and piston rings.
• If the bores are becoming worn, a set of Cords rings, which ‘cut’ a new bore (check if they are still available for your car) may save you expense of a proper rebore.
• If there’s serious wear present then you’re wasting good money carrying out anything short of a full overhaul. An alternative is to find a good second-hand engine at a breakers or autojumble although you need to have a sound knowledge about engines and how to check for wear – or you could be buying a unit that’s as bad as the one you already have!
• With the sparking plugs removed, see how easy the unit turns over by hand and look for signs of any recent work carried out such as fresh gaskets, clean oil, lick of paint and so on.
• Check with an engine specialist or owners’ club to ascertain any known weak or wear spots on your car’s engine and the likely costs of common repairs.
• A compression test tells you a lot. The readings should be uniform; if not carry out a ‘wet test’ by adding a few ccs of oil down each bore. If the readings improve, it points to suspect cylinder bores and pistons.
• Bore wear can be gauged both visually and by touch. If there’s undue scuffing then the rings have ‘picked’ up on the bores. With a piston at top of the block can it be ‘rocked’ excessively, pointing to wear? If all is okay, simply fit new piston rings but check first whether you require ‘oversized’ ones due to the fact that the engine has already been rebored.
• Even if the bores show signs of wear, an expensive rebore may not be needed if special oil control rings that ‘re-cut’ the cylinder can be sourced, usually via engine rebuilders.
• With the cylinder head off, take the opportunity to have new valve guides and hardened valve seats installed so the engine can happily accept unleaded petrol in the future. At the very least, give the cylinder head a thorough decoke, lapping in the valves and renewing the valve springs and seals, if fitted.
• Sourcing another engine gives you the ideal opportunity to upgrade at the same time, such as slotting in a 1.6-litre unit where a 1.3 used to reside or a unit from a sportier version, like the GT in the range? Spitfire engines in Heralds and 1275cc Midget units powering Morris Minors spring to mind here and the good news is that classic car insurers (mindful of parts availability) are pretty relaxed about this sort of thing. So long as you tell them probably won’t affect your insurance at all.
• If you’re considering a new power unit there’s three states of quality available and you get what you pay for: Remanufactured, Reconditioned and Rebuilt and their terminology is important. Remanufactured means that the unit is returned as close to as new as possible, reconditioned usually points to a unit where only worn parts are replaced or overhauled while rebuilt can imply that the engine was simply taken apart and rebuilt with new gaskets and oil!

DON’T FORGET THE TRANSMISSION

If the car was bought as a non-runner, then you have no real clue to how worn the gearbox and final drive units are, apart from checking the condition of the oil. A metallic silvery taint suggests of a bearing failure, for example. If you can remove a ‘top plate’ on the gearbox, turn the mainshaft and have a look at the cogs as you do, checking for general wear and chipped/missing teeth. If the transmission comes with a gear lever, select all ratios, noting any slop present.

Do a similar job on the rear axle by removing the ‘bango’ casing. If the axle has come complete with halfshafts, check for wear and shunt. The good news with most transmissions is that they are usually pretty long lasting so you can take a chance and see how they perform on the road rather than automatically overhaul. Do change all oils though and if you have split the engine from the ’box, renew the clutch assembly.