WIRING GP-ENGINE 3240696 - Caterpillar

G379, D398, G398, D399, G399 Commercial EnginesDiesel and Gas cylinder heads for the 6.25 bore V engines can be machined from the same basic casting. This has caused confusion for some dealers and customers. Although both heads can be machined from the same casting, a head that was originally machined for a diesel head may NOT be satisfactorily remachined into a gas head.
When a 6.25 V head is machined for a diesel application the intersection point between the center of the bore on the prechamber and the bottom deck of the head is 23.77 mm (.94 in) from the centerline of the cylinder. When a head is originally machined for a gas application the intersection point between the center of the bore for the spark plug adapter and the bottom deck is 26.99 mm (1.06 in) from the centerline of the cylinder.
If a dealer or customer reworks a diesel head into a gas head the intersection point ends up 3.22 mm (.13 in) too close to the centerline of the cylinder and hence too close to the valve seat of the V bores. A head reworked in this manner is NOT acceptable to Caterpillar because bottom deck head cracking may occur under normal operating conditions.
Heads reworked in this manner are NOT acceptable for core credit on a reman cylinder head from Caterpillar.