The Volkswagen Type 3 Motor, also known as the pancake motor (a name it shares with the Type 4 motor), is basically a VW Type 1/ Type 2 motor with a rearranged cooling system.As with Type 1 motors, the engine is composed of 4 horizontally opposed finned cylinders which are cooled by air. The engine has 8 vavles actuated by a central camshaft and pushrods. The engine is cooled by the a constant supply of rapidly moving air as opposed to the flow of coolant found in most car motors. Oil also plays a large part in cool the motor, and VW air-cooled motors all have an oil cooler. Due to its air-cooled nature the Volkswagen engine lacks a whole system of moving parts, increasing it reliablity. In the T3 motor the fan is attached to the end of the crankshaft, where the fan pulley is normally attached on the T1/Beetle. The fan rotates at the same speed as the engine and drives a generator via a pulley and a belt. The air is vented from the fan back across the engine over the cylinders and through a doghouse style oil cooler that lies flat against the crankcase. Although contrary to popular belief, the T3 pancake cooling system cools more efficently than the T1/T2 upright cooling system and does not have problems with fan belt breakage (if your belt breaks, your generator doesn't work. Thats it.)
The T3 motors came with several different fuel systems. The earliest was a single centermounted Solex side-draft carb. After a few years dual solex carbs were introduced. These are similar to the Solexes used on early Type 4 powered buses and the dual Brosol carbs now sold in kit form for the T1. These 32 mm carbs (Solex 32 PDSIT 2/3) gave the T3 an extra boost in horsepower and general improved the type 3 in many ways, including fuel economy! In 1967/1968 the Bosch D-Jetronic electronic fuel injection system was introduced on North American Type 3s. This system was one of the first fuel injection systems to be used on family cars. This fully electronic system derives its name from Drucke- Jetronic, as it is metered via the the pressure/ vacuum in the intake manifold. It was a multiport injection system that later found its way into Volvos, BMWs, Saabs and Caddys. This system provides superior fuel economy and power and was hailed by the automotive press as the introduction of a new era of fuel supply.
The actual T3 crankcase is basically that of the T1. It shares all internal components and is only different in the location of the dipstick/ oil filler hole. The hole in the T3 is located near the bottom of the case, but can be blocked of if the case is to be used in a T1 engine application. The other major difference is the presence of a few tapped holes for a rear engine mounting bracket that sits at the back of the case, similar to that found in some T2s (buses). Many universal cases come with these holes, and a block off plate, allowing the crankcase to be used in either a upright T1 motor application or in a T3 pancake engine application.
T3s initally came with motors of greater displacement and horsepower when compared to T1 and T2 upright motors. T3s got the first 1500cc motors (hence their true model name, the Volkswagen 1500) with the 1600cc motors following soon after. The Type 34 Ghia came with different motors that had different pistons that produced a higher compression ratio than other Type 3s.