Sporting XJ-6 Project
This 1972 Series 1 XJ-6 sedan came to us with some runability and drivability issues and a few modifications already complete on its way to becoming a high-performance street car/competitive club racer. The main thrust of the project is to enhance the performance and handling of the car by turning the original 4.2 liter engine into 5.0 liters with Stroker crankshaft and modified camshafts and then fitting Mallory CD ignition, a Tremec 5-speed transmission and a Pow-R-Lok differential to the car. (The car came to us with tubular headers and triple Weber carburetors already installed.) We started with the engine.
The plan for the engine involved using the original 4.2 liter block with a Series 3 big valve cylinder head with Crane high-lift 250º cams, a Crower Stroker crankshaft with matching "long" Crower rods connected to short-skirt, high-compression, forged Arias standard bore pistons. (We could have ordered oversize pistons but since we are already at 5.0 liters the piston size is not of huge importance so we used pistons that were available instead of waiting for a special order.) The Crower crankshaft uses GM bearings so the block was align bored to fit the GM bearings.
One of the main challenges of this project was fitting the 5.0 liter Crower Stroker crankshaft into the original 4.2 liter block. At every stage of fitting the crank and the rods we had to check for interference and grind out places on the block and the oil pan to create enough clearance. We ended up clearancing four spots on the block to create enough room for the connecting rods.
The oil pan was modified by sawing the rear of the pan off so that the new positive crankshaft seal holder would fit with the oil pan. The sides of the oil pan had be ground out in 12 places, 6 on each side, so the connecting rods would have enough clearance.
The Arias pistons we installed have domes that reflect the location of the different positions of the combustion chambers in the cylinder head. We used calico-coated bearings with the Crower rods and ARP bolts. We also used German timing chain. We use only German timing chains on modified motors because of their high quality.
Also utilized was a Gran Turismo racing oil pump provided by the owner that was intended to be used in conjunction with a dry sump set up. The main advantage of this pump is that it is capable of pumping more oil than the standard oil pump. The pump did have to be modified to fit to the block. The lower plate of the oil pump had to be clearanced because of interference from the crankshaft front counterweight. The boss for the oil pump bypass spring adjusting screw also had to be adjusted for oil pipe clearance and the bypass adjusting screw had to be shortened significantly.
The inlet and outlet fittings for the pump were created by modifying AN fittings which were then screwed onto modified brass street elbows. (One interesting design feature of the Gran Turismo pump is that the inlet and outlet are reversed from a standard Jaguar oil pump.) The oil pipes are curved to allow for expansion and contraction. They were created from two suction pipes and three discharge pipes that were cut and welded in four places. An E-Type strut was added to keep the oil suction pipe from twisting and interfering with the crankshaft.
We drilled the block between the cylinders to match the extra cooling holes in the Series 3 big-valve head. After we installed the cylinder head we also installed an early sedan oil filter and housing to facilitate test running the engine before it is installed.
We have rebuilt a 354 Pow-R-Lok differential to replace the original open differential to better handle the increased power of the engine. The next step is to test run the engine and then get it in the car.