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One of the most distinguishing features of the Jaguar XK engine is it’s DOHC camshafts which allows for an optimal combustion chamber shape and better flow from the intake to the exhaust. The first step was to get the cylinder head off which corrodes slightly where the aluminum head meets the cast iron block which can be avoided with anticorrosion in fresh antifreeze. After a good clean, work on the valves, seats and stems is critical for the rebuilt. In our case both valve surfaces had to be reground to ensure an optimal seal in the chamber, but the stems were great which is a good sign that the engine has never overheated.
The valve seats were ground with a special stone attached to a canted drill and the valves themselves were reground in the refacer machine. The clearances are set with shims on the top of the valve stem.
Made from aluminum, the cylinder head was fitt onto the cast-iron block while the block was already in the car. It weighed 60 lbs before the valvetrain was fitted so a hoist was necessary with the front hood tilted forward. Hylomar sealer was used to seal the gasket to the block and head and limit corrosion.
Naturally a new clutch was ordered and was sent away to be balanced as a single unit with the flywheel. Since the inline-6 has inherent primary and secondary mechanical balance, the flywheel doesn’t need to be exceptionally large as in a V8 or inline-4. The total weight of the standard flywheel and clutch is 40 lbs.
Made from a single piece of steel (instead of cast iron), the ring gear is integrated into the flywheel and gives Jaguar engines a distinct ring noise on start. Unfortunately this also means it can not be repaired easily if there is tooth wear from the starter. If a tooth breaks or there is a trouble spot, the Jaguar manual says to replace the entire unit. Another fix is to machine the entire ring gear off and have a modern replacement shrunk on.
The flywheel has drill holes where the machine shop removed weight from the flywheel to ensure a better rotational balance at all rpms.
With the crankshaft and distributor mounts in place, the next step was to install the pistons & conrods. For comparison we show one of the high-compression 9.0:1 pistons used for the E-Type and the 8.0:1 used on the saloon cars. The carbon buildup on the dirty piston is typical of oil burning and rich mixtures in the chamber. In extreme cases this can build up, increase compression and cause detonation.
The pistons and rods looked to be in good shape but some elementary mistakes were made during the last build. For instance the gaps in the piston rings were lined up which increases chance of blow by. In the manual jaguar recommends to replace all the connecting rod bolts.
Below is one of the new bearings and an old one that is indicative of problems that can arise if oil is not changed regularly. Near the oil supply hole, a rigid line was carved out of the bearing from particulates in the oil. Such a scenario can increase heat and create resistance. The last bearing shows typical wear on a main bearing.
The last step was to check all the ring gaps and install the pistons using a ring compressor.
Having repaired the Jaguar 4.2 block with the Lock-N-Stitch process, assembly could begin from the bottom up. The first step was to hone the cylinders and ensure a smooth surface for the piston rings. With some oil applied to the abrasive stones each cylinder got around 20 to 30 strokes.
This engine shows signs it has been apart before. Aside from the factory labels of JVC1 through JVC7, several other marks were on the block. Typical of airplane construction, JVC1 was closest to the firewall.
The first step was to fit a rope seal which needs to be evenly pressed into place. These two-peice seals create a tight fit because the inner surface of the seal is rubber which expands when exposed to oil. Installation was done with a unique tool with a tapered surface that expanded the seal into place. A fitting on the end of the tool let us rotate the tool to avoid any binding.
Next the bearing clearances were tested with the main bearing caps fully torqued. After establishing good clearance (.002 shown), the 75 lbs crankshaft could be permanently installed with new bearings and thrust washers. Not long afterward the end play of the crankshaft was measured using a dial gauge which was magnetically fastened to the block. Typical play is .002 to .003 to a maximum of .005. If the end play was too much, oversize thrust washers would be needed.
Finally, distributor drive spindle was fitted using a modified distributor. This ensured that the torque wasn’t applied to the gears and instead the linkage of the distributor.
Having received all the necessary tools and supplies from Lock-N-Stitch in Turlock, California, we could begin the process of repairing our Jaguar 4.2 block. The company provides an informative DVD that explains all the steps and options which is essential. The basic idea is to replace the crack with a linear line of screws and begins with a single drill hole that will is placed well beyond the crack to ensure strength.
The above photos show the Lock-n-Stitch spacer which inserts into the first drill hole and lines up the drill bit for the next cut. The tool isn’t completely necessary, but it organizes the holes neatly and ensures proper distances between screws. For the first run, only every second screw is inserted. The holes are then countersunk with a spot face bit that will cut a controlled shoulder for the screws. The spot face distance is critical and depends on the wall thickness and thread distance.
The first set of cascading drill holes are then threaded and the pins/screws are inserted permanently into the block with thread sealant. The screw is simply wound into the block until the breakaway head shears off. The remaining stubs are then ground down so the gaps inbetween the screws can now be filled with the second series of screws. The following picture shows the second line of pins being inserted with the breakaway top of a single screw resting on the block.
After the complete line is finished a needle scaler was used to replicate the rough finish of the block. The end of the screws were left slightly protruding to retain as much strength as possible. The following picture shows the needle scaler and a finished line which was pressure tested to 10psi for leaks.
Since no bubbles were visible from the pressure test we can now begin assembly of the 4.2 engine from the bottom up. Below is Lock-N-Stitch’s own promo video for their product.