4.2L 258 I-6
From JeepForum.com Community Jeep Wiki
The 258
This iron block 258 cubic inch I-6 cyl was introduced in 1971 and stayed in the jeep family until 1990.
Gladiator/J-Series Trucks pickups and the Wagoneer were the first to use this engine. In 1972 the CJ's (including the CJ-5) were powered with this reliable mill. And finally, In 1987 the YJ Wrangler used the low end tourque and HP from the venerable '6' until the end of 1990 when the 4.0L I-6 took over. When comparing the later 4.0L and the 258 the main difference is the stroke of the pistons (3.41" and 3.90" respectively). The 258 has a cast iron block and cylinder head, hydraulic lifters (non-adjustable rockers), and 7 main bearings. The main strengths of the 258 are it's reliablity, low cost, low RPM horsepower and torque peaks, and serviceability. It's biggest weakness is the Carter Carb.
This engine came carbureted from the factory, and used either the Carter BBD (double barrel) or Carter YF (single barrel) carburettor.
Specifications
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 9.2:1 |
| Horsepower (net) | 112@3200 |
| Torque (net) | 210@2000 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Firing Order | 1-5-3-6-2-4 Clockwise(see image) |
| Fuel | Petrol |
| Carburettor options | 2 Barrel Carter BBD |
| 1 Barrel Carter YF |
