Ford sent the stock 390 engine from the factory with impressive horsepower. The company made it easy and cheap to modify with aftermarket parts and a little time in the garage with decent tools and a basic knowledge of car repair.
The most common 390 engine produces 315 horsepower at 4,600 rpm without any changes. The carburetor is a mildly inadequate 446 cfm four-barrel coupled to a low-profile manifold. The compression ratio of 10.5:1 doesn't need to be changed. Some Ford products were given a 390 with a two barrel carburetor and a lower compression ratio of 9.5:1. It's rated at 265 horsepower at 4,100 rpm. If this is the only engine available for modification, it will need new pistons and accompanying hardware to bring the compression ratio up to 10.5:1. Ford made a few 390 4V "GT" engines with modifications from the 428 Cobra Jet engine, which can deliver 325 horsepower in stock configuration. This upgraded engine comes with a Holley four-barrel carburetor capable of sending the fuel/air mixture to the cylinders at 600 cfm through a medium-rise manifold. Ford installed the same cam and valve train as with the 428 Cobra Jet.
Car Craft magazine upgraded a 390 with bolt-on parts bought from aftermarket retailers. It wanted to enhance the engine with the same cost, talent and tool limitations the average garage mechanic would face.
Car Craft began with a new stroker kit that included a new crank, rods, pistons, rings and bearings and gave the engine 446 cubic inches of displacement. It had the engine balanced by a local shop. The cost for the kit was $1,949 in 2008. The stroker kit could be installed by a good garage mechanic because it simply meant tearing down the engine then reassembling it with the new parts. Cost of balancing depends on the local market.
Car Craft installed new Edelbrock FE heads, which provide good fuel/air flow without porting the stock 390 heads. It kept the factory valve train and solid lifters. It put in a new Holley carburetor, intake manifold and headers and, aside from a few repairs for the individual engine and minor parts, kept everything else stock.
Any engine upgrade should include replacement of the ignition, coil, distributor and fuel pump.
The cost for all of the materials Car Craft used was $6,000, not cheap but reasonably within reach of the average consumer. The initial cost for the engine was under $200. The engine could be installed in any number of Ford cars or trucks at low cost.
The dynamometer read 500 horsepower and 500 foot-pounds of torque.
