Rebuilding the Healey Six Cylinder
by Tom Mason
Originally published in the Austin-Healey Magazine, November 1990
Rebuilding the Healey engine is within the ability of any owner. These engines are tough, reliable, torquey, and powerful for their size. While they may not be sophisticated, they are much more reliable than some sophisticated engines that have a habit of not working. They were built before fuel efficiency and emissions were a design criteria and it is not fair to judge them on these counts. However, the engines approach one hp per cubic inch.
Mileage on the engine is a factor in rebuilding. A 100k engine will need more work than a 50k motor. Generally it is a good idea to have the block boiled out and bored by a machine shop. If the cylinders are worn. it will have to bored out to +.020, .030 or .040 with the expense of new pistons. If the cylinder wear is minimal, simple cross hatch honing will suffice. Moss motors has original paint in spray cans: primer the block first. Ok your block is ready so...
Do the connecting rods next. They need to be sized by a machine shop for about $7-$ 10 each. The shop grinds a small amount off the caps, bolts them back together, and rebores the holes to an accuracy of ten thousands of an inch. Do not skip this step...
Piston and Crank
Install new rings and put sized rods on the pistons. Use a ring compressor and install piston in their bores. Buy a crankshaft micrometer and mike the crank. The specs are in the service manual.(Note a standard rod bearing is exactly two inches.) Nice! Tight running clearances generate longevity in an engine. Plastic gauge should be used as double check on clearances. A crank that is not worn can be used with standard bearings. If worn, have it ground to -.010 and use oversize inserts. Install crank and rod bearings and torque to specs. Note that the connecting rods are offset and face each other. Pistons are marked "front". Mounting the engine on a mechanics creeper is a good way to work on it and you can roll it around. Install the endplates and flywheel. Be sure to replace the transmission oil seal while the engine is out, also the throw out bearing and clutch disk. The flywheel should have a smooth surface or should be replaced. Some of you may want to have the pistons weighed and the engine balanced. It's not a bad idea for a hundred or so. There is a pilot bushing in the end of the crankshaft to support the transmission end shaft, it drifts in and out so don't forget to replace it.
Have the camshaft ground and install new tappets/lifters: these are expensive but a must. The lifespan of the oil pump is about 100k. Oil pumps are hard to find and expensive but they also are a must. The earlier vane type is a better pump. You can get rebuild kits from AH Spares or SC Carbs in England. New gears and a shaft are an ok repair, but the pump needs to be run on a drill to wear in a little before installing. Install the oil pan. I like to glue the gasket to the pan and use no sealer against the block. Turn the engine over on the cart and add the oil pump, distributor, and galley covers.
This pretty well covers the bottom end. I like to reinstall the engine and then add the cylinder head. I find this easier, as the engine is heavy enough without the cylinder head and you are less likely to damage the paintwork. Bronze guides and hardened exhaust seats are available. These have teflon oil control rings and are well worth the money. Porting and polishing is up to you. I have a spare head and I'm trying it out, but I can make no comparison just yet.
Starter, Generator, Water Pump
Put new bushings and brushes in the starter and generator. Turn the commutators only if they are really rough, I have my original starter and generator still on the car at 120k. Water pumps can be rebuilt with a new seal if you can find one. The earlier water pump is preferable and it will fit all engines.
A portable hoist is available from rental agencies. After the block is back in and bolted up to the bellhousing. reinstall the head with manifold on and carbs off. Torque the head and adjust the valves. It is common to get the distributor out 180 degrees so don't despair if it backfires when you try to start it. Static time the ignition per the manual. I like to turn the carb screw mixture up till they are flush with the brass housing in the carbs. You can see this if you remove the carb tops and look at the mixture needle housing. Then turn both mixture screws down 10 full turns [360 degrees] and this will give a grossly rich mixture. Bring them back up, a turn at a time, and the idle will increase. At the point where the idle stops rising is about the right mixture. A new engine will require fine tuning for awhile to get everything just right. Keep a screwdriver and drive around till it gets just right for your driving.
If you think about it, you should be able to start with a virtually new engine and a car that is the equivalent of a new Healey mechanically. As good as new so to speak. I have redone three motors and I bought a junk engine for my 3000, that I am building up to be a spare for 10 or 15 years from now, as my current engine was rebuilt at 100k and has only 20k on it now. I feel the car is mechanically the equivalent of new and it runs that way. Good luck with your car!
Not what you were looking for? Don't forget you can check our back issues using the AHCUSA Magazine Index.