Lots of people with 350 cube Chev V8s under their bonnets claim to have 500+ horsepower. In fact, any ol' modified Chev would have that much, wouldn't it? Not bloody likely! Here we cover the mechanical make-up of a 350 that punched out no less that 535hp on the engine dyno - and there's no bodgy conversions from rear wheel power figures being used here!
The engine was built by John Keen on behalf of a customer who insisted that the magic 500hp figure be reached.
John started with a 4-bolt 0010 350 block of the sort fitted to the early Holden Statesman. The block was over-bored 0.040 inches, decked by 0.003 inches, and then tunnel bored. To aid oil return to the sump, the inside of the block was laboriously polished using a die grinder. Steel main bearing caps (rather than cast iron) were selected for use.
Into the block went a Cola forged billet steel crank spinning in Clevite H-series bearings. On the big ends are Clevite P-series bearings, easing the friction from the 6 inch Eagle steel H-beam rods. Perched on top of the rods are forged JE pistons - with a Felpro 0.040 inch head gasket, they give a compression ratio of 11.7:1. The pistons wear TRW "file back" rings. As you might expect from that comp ratio, the engine drinks 100 octane Avgas.
The heads are Dart Sportsman cast iron units, heavily ported by F&M Cylinder Heads. Intake valves are 2.02 inch Manley stainless, with exhausts comprising 1.6 inch examples of the same make. On the flow bench the intakes recorded a peak flow of 277 cfm (at 28 inches of water pressure differential) at 0.700 inches valve lift. However, the flow starting severely tapering off from around 0.500 inches lift. With the Victor Junior manifold in place (but not topped with the Holley) the flow dropped by only a tiny amount. On the exhaust side, the maximum flow of 272 cfm was recorded at 0.700 inches lift, but again flow started tapering off severely from around0.500 inches lift.
Making the valves open and shut is a flat tappet Crane 111501/F268 solid lifter cam. This runs a duration at 0.050 inches lift of 268° (inlet) and 276° (exhaust). Lift is 0.572 inches on the inlets and 0.590 inches on the exhaust side. The lobe separation is 106° . The cam was installed "straight up", ie to the manufacturer's cam timing marks. The valvetrain is all from Crane - Energizer roller rockers (1.5 ratio on the exhausts and 1.6 on the inlets), 7/16 inch studs, guide plates and heavy duty moly thick wall pushrods.
The intake manifold is a Victor Junior single plane design. A Holley 750 Double Pumper carb sits on top of this. Dyno testing was carried out with and without the aircleaner in place; despite the tight clearance between the aircleaner and the carb mouth, the engine's power output remained the same.
A Mellings Big Block oil pump keeps John Keen's favourite brew circulating - six litres of ULX-110 is used in the Miloden sump. A Manley windage tray fights against oil starvation and frictional drag. Extractors are mandrel bent Pacemaker units, using 43 inch long 1¾ inch primaries, 7 inch long 3 inch diameter secondaries, and a 4 inch outlet flange.
Firing the cold NGK BP7FS is an Accel magnetic trigger dizzy working with a Crane Hi-6 Capacitor Discharge Ignition. The Hi-6 uses a sequential rev limiter set to 6900 rpm limit. Leads are Accel 10 mm and the coil is from Crane.
So what did the owner get for his A$17,000? On the Allan Engineering eddy current engine dyno, peak power of 535hp was reached at 6000 rpm. More impressively - especially for an engine to be used on the road - is the very strong torque curve. At 3000 rpm torque is already 445 ft-lbs and rises to a peak of just over 500 ft-lbs at 5000 rpm. In fact, between 2500 and 6400 rpm the torque never drops below 400 ft-lbs!
Contacts:
John Keen + 61 8 8277 4222
F&M Cylinder Heads + 61 8 8294 2515
Allan Engineering + 61 8 8522 1901
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