the racing version of the Capri RS 3100, competing successfully in the European Touring Car Championship, as well as in Formula 5000 single-seaters. One hundred kits were also sold by Ford Motorsport. Ford RS dealerships also offered a number of performance modifications for the Essex V6, called the "GP1" (Group 1) and "Series X", the GP1 package offered a 40 DFI5 Weber carburetor, a camshaft kit, larger, , inlet and exhaust valves, double valve springs, specially selected connecting rods and forged high compression pistons giving a power output of around . The Series X modifications offered the same larger inlet and exhaust valves as the GP1, but also offered a new inlet manifold designed for three twin-choke 42 DCNF Weber carburetors fed by an electric fuel pump which boosted power up to and , however the standard camshaft was retained. Earlier versions of the 3.0-litre engine (pre-October 1971) were fueled by a twin-choke 40 DFAV Weber carburetor, which had some inherent faults in its design which caused it to run too rich and cause bore wash. It was subsequently replaced by a more modern twin-choke 38 DGAS Weber carburetor which effectively solved the problems of the earlier carburetors, and was used for the 3-litre V6 until the end of its production. The 2.5-litre V6 used a single barrel Ford carburetor which was also used in the low-compression variants of the 3.0-litre Essex V6 used in the Ford Transit. Unusually, the Essex V6 was designed so that the same block could serve in both diesel (compression ignition) and petrol applications, although the diesel version never reached production. Traces of its diesel design lie in the very heavy construction using Heron cylinder heads and the necessity for dished pistons to decrease compression for the petrol engine. The cast iron Essex V6 is a heavy engine due to its sturdy design weighing in at , more than the aluminium alloy Rover V8, for example, the Essex V6 also has a very heavy yet sturdy four-main bearing crossplane crankshaft with large main journals, and a heavy flywheel in order to smooth out the power delivery, sometimes Essex V6 engines are referred to as an "Essex lump" referring to the weight of these engines. In spite of its heaviness, the Essex V6 was used as the main workhorse and a high performance option for medium to full-sized cars like the Capri the Granada and Transit.