John Maher Racing engines have a reputation for providing more power and reliability than other engines of similar specification. This is only achieved by ensuring top quality components and precision engine building techniques are used. Having equal deck heights and combustion chamber volumes, balanced rods and pistons, a dynamically balanced crank assembly (crank, flywheel, pressure plate and crank pulley), dialled in cam, honed cylinders, gapped piston rings, precision multi angle valve job, match ported manifolds and correctly jetted carbs are just some of the things that have to be right if the engine is to perform as expected. The compression ratio must be matched to the engine spec and the kind of vehicle it will be fitted to i.e consideration must be given to the weight of the vehicle and how much cooling air is able to enter the engine bay. Also important, is the correct matching of components. An engine consists of a multitude of individual parts. Choose one wrong component and you stand a good chance of upsetting the performance potential of the engine or even a catastrophic failure. After years of experience building and testing different combinations on the road, track and dyno I know what works. When a customer commissions me to build them an engine, they are benefiting from that knowledge and experience. Don’t pay good money to be someone else’s guinea pig.

Before any of my engines leave the premises, they are dyno tested. Prior to testing under full load, the engine is spun to build oil pressure. Then I break in the cam; 20 minutes at 2500 rpm. Next, each cylinder is leak tested to ensure the piston rings are sealing and the intake and exhaust valves aren’t leaking. Having passed this test, the engine is tested at full throttle throughout it’s operating range to arrive at correct venturi, main jet, air corrector and idle jet sizes for the carburettors. Each engine is supplied with a computer print out displaying torque and horsepower developed on the dyno. Only when an engine has passed all these procedures is it deemed ready for collection or fitting.

	Click here to go to the JMR engine calculator Calculates compression ratio, deck heights, head cc and engine capacity

99% of all machining operations necessary to build a performance aircooled engine properly, are carried out in house.

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