Engine

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The MGA had a variety of engines:

• 1500 early (1489cc) 68 bhp
• 1500 late (1489cc) 72 bhp
• Twin Cam (1588cc) 108 bhp High compression
  
• Twin Cam (1588cc) 100 bhp Low compression
• 1600 (1588cc) 78 bhp
• 1622 (1622cc) 93 bhp

Although no real outstanding horsepower here from today' s standards, when these were first produced they won a great many races. Even today on the vintage racing circuits, MGAs are winning their share of races.

My car came with a 1600 engine, of which the previous owner had no history of. 1600 engines are found in a variety of British vehicles and have been around for many years. My block is undoubtedly from an MGA due to the cutout in the block to allow a mechanical tachometer. Although the 1600 is not stock for my  particular MGA, I do appreciate the upgrade in power. Most of the MG community is accepting to interchange different engines sizes between different years, or even going as far as using a MGB engine and still being called "original". The early 3 Main MGB engines are virtually a dropin exchange where as the later 5 main blocks require a little work, i.e. matching various  components from the MGA (1500,1600,1622, & 3 main 1800, depending on which transmission your using, as well as using an earlier front plate, which use the rectangular engine mounts.

When I dismantled the engine I discovered (after some head scratching) that I had 1622 pistons and rods in a 1600 block. Someone had tried to replicate a 1622 engine. The block had been bored out to 3" (.030 over) to except the 1622 pistons. Along with the unusual components, the pistons and rod bearings were slightly scored. The block and crankshaft looked quite healthy.

I had a machine shop go through the engine, they cleaned up the cylinder walls and polished the crank. The machinist mentioned that the bores were not consistent through the whole cylinder, which would explain why the pistons were scuffed and perhaps adding extra strain to the rod bearings. The engine components were balanced, the block hot tanked and new cam bearing installed. It looked great and ready to be rebuilt. The crankshaft, camshaft and piston rods will be the only things not replaced.

The 1622 engines, besides having a bigger bore also have higher compression pistons, this in combination with a newer style head produced 93bhp. The 1500 & 1600 engines, both used a dished top style piston and and a cylinder head with a 37cc combustion chamber, producing 8.3:1 compression. The 1622 engines used a flat top piston and a 43cc combustion chamber, producing 8.9:1 compression So in an effort to grab a few more horsepower I decided to go with the higher compression pistons as well, which means I need to replace the original head (compression ratio would be to high with the old head). Running the engine the way I found it  would have produced a very high compression of around 9.6:1 and would have required very high octane fuel to combat pre-ignition and engine life would be shortened. Since the proper1622 (43cc) heads are very hard to find, I have bought an early MGB (1800) head, these heads are interchangeable and are a lot more common. This head is very similar to the original 1622 head, with the combustion chamber and both exhaust and intake valves all the same size. So on paper I should be getting close to 93 bhp. The head will also be ported and  polished to allow for better air flow. That should make my silk scarf stand up in the breeze.



The original oil filter cartridge system has been converted to except the modern spin-on filters. Oil changes will be a lot easier and cleaner.

The 1622 and early MGB flywheels were lighter for added performance. The earlier MGA flywheels can be easily lightened to match. I had a machine shop lighten my flywheel by a few pounds, it also needed to be re balanced. This could add a couple of hp and improve the throttle response, although losing the extra weight will make it easier to stall from a dead stop. The ring gear was replaced at the same time.

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Although I have all the parts, I'm hesitating actually rebuilding the engine. I would like to wait till I get a little closer to having the car complete so the engine is not sitting around and possibly seizing up or maybe creating some extra wear when it does finally get started.


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