However, Toyota incorporated lessons learned during the war, and the F engine benefitted from lightweight alloy pistons and better lubrication than earlier models.

The cylinder head and combustion chamber is derived from the Chevrolet L6 OHV "Stovebolt" engine, slightly scaled up.

The general idea was consumers would feel comfortable with the engine since it was a familiar design and had a proven track record.

First introduced in export models of the 4-ton BM (FM) truck in November 1949 with 6.4:1 compression and 95 PS (70 kW), it then found its way into the Toyota FX/FZ in September 1951.

[1][2] Beginning in 1954 it became installed in the long running FA/FC series of trucks; this was also when the combustion chambers were reworked and the compression ratio was increased, upping output to 105 PS (77 kW).

This remains a 3.9-liter, 75/93 kW (105/125 hp), carbureted gasoline engine capable of 261/289 N·m (189/209 lb·ft) of torque at 2000 rpm; the major difference between the F and the F.5 is the oiling system.

Differences from the 2F engine include a modified cylinder head to reduce warping and separation from inlet and exhaust manifolds, the introduction of electronic fuel injection (EFI) in some markets, a vastly improved emissions system, and a smaller displacement resulting from a shorter piston stroke.

Due to the low rpm design and cast iron construction of these engines, it is not uncommon to see them reach over 480,000 km (300,000 miles) before needing a major overhaul.