The Magnus high performance stroker kit for McLaren M838 engines.  Enlarges your displacement of your 3.8L Mclaren 570 – 650 or 675 to the 4.0L engine featured in the 720 and 765 and 750

all parts are included to convert your 3.8L Mclaren engine to 4.0L Providing increased horsepower, throttle response, and specifically designed to accommodate the increased loads on your engine.

Featuring a billet crankshaft (standard 720 Mclaren stroke), Custom Magnus designed sleeves, custom pistons and custom Billet 4340 Connecting rods an pins. Including a friction washer, piston rings, Main bearings, thrust bearings and rods bearings, main bolts, head studs, and all gaskets needed.   

Everything you need to do the engine perform this engine conversion.

Early on we discovered that many Mclaren engines would suffer rod failures, most of them were mainly cars with just a tune and exhaust.  The extra tq that was developed put the piston and rod combination out of its design parameters.  Because the Mclaren pistons have a very short strutted skirt design and a piston guided rod, this allows for less friction.  The rods are not touching each other on the crank as a standard V8 is they are spaced 10mm apart from the crank radius and each other also to aid in lower friction.   At the same time this low friction modification has a bad side effect for big power engines, it also allows for movement away from true perpendicularity of the rod and piston. The piston and rod can move away from the crankshaft and bore centerline, becoming not square in the bore.   High torque, low friction short piston strutted design piston, and no ability to keep the piston square in the bore or on the crank pin will almost always result in bent rods and then further catastrophic failure, usually ends with a hole in your block.

Our proprietary Connecting rod and piston design fix a key problem in the 838/840 engine families ability to handle very high horsepower and hi torque situations.  We changed the Mclaren’s piston guided small skirt rod to something a little beefier that helps keep the piston square in the bore and we have made connecting rods that guide the rods and keep them 90 degrees to the crank.   This modification is in all of our high horsepower Mclaren builds.  Rod guided pistons keep the pistons and rods square in the bore and stop the unexpected bending of the connecting rods in high torque situations.   Our internals are estimated from experience to be good for over 2000hp, but currently clutch technology has not been able get a clutch into a Mclaren that can handle more than 1350 hp.  All of our stage 2 Mclaren engine builds feature Rod guided pistons

Please contact us for purchase

Part Number 

MMCENG7270 Magnus McLaren 4.0L M838 to M840 Stroker Kit

Additional information

Weight 5 lbs
Dimensions 6 × 6 × 6 in

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