Jaguar head case sorted
Acouple of months ago the E-Type had been booked into an annual Jaguar Club organised car show that's held on the front lawn of one of the members country property. This event is a private ‘invitation only’ affair with limited car numbers and no spectator entry and is a super day spent talking to other enthusiastic car owners. Obviously there was no chance the Jaguar would be mobile, so I advised the organisers I would arrive in the Stag, so they switched my allocated parking area to the Triumph rather than Jaguar area.
The weather for the day was terrible, varying between heavy rain and light showers, resulting in over 100 cars failing to turn out, which was a shame as the entry fee was going to assist the local drought affected farmers. However the downpour here in Australia was probably a better gift for the farmers than financial assistance but unfortunately for both farmers and show organisers, this had been the only wet day we’d experienced in the past few months.
Anyway, back to the Jaguar. The lapped valves were installed into the head and fitted with springs, collates and top collars. A couple of points in the assembly procedure to note when there’s a steel collar around the valve guide where the valve springs sit. This can fall out during cleaning the head, so care needs to be taken that all of these collars are in place prior to installing the valve springs. Also my understanding is that early E-Type engines weren’t originally fitted with any form of valve stem seals. There aren’t any shown in the parts book and the gasket kit doesn’t contain any.
However, I do like to fit the stem seals onto the inlet valves as fitted to later 4.2 engines, so always order a set as separate items. During the strip down I’d segregated the old valves, shims and bucket tappets so they could be re assembled into their original location to assist with adjusting but having replacement valves made this superfluous.
I did however ensure that all the tappet buckets went back into their original guides. I only have a limited selection of tappet shims, so selected the six thinnest and fitted these to one set of valves, followed by the camshaft complete with a plate with a centre hex drive bolted fitted to the end so a spanner can be used to rotate the camshaft for the measurement of clearances. After measuring
the gap between each camshaft lobe and tappet, the correct sized shim was calculated after removing the cam to check if I had any of the right thickness.
Unfortunately, in most cases my somewhat limited shim stock never delivers the correct thickness, so the next thicker one was selected and ground to the required size using a small surface grinder. Once again it was necessary to go through the process of refitting the shims and camshaft before measuring the gap again.
In most cases this second measurement was correct, but on a couple of occasions where the initial gap was quite large, it required a multiple thickness of feeler blades to obtain the correct measurement. The gap was less than specification and required the cam to be removed and an additional shim grinding. When I was completely happy with the first side, that cam was removed and the process repeated for the other row of valves.
Both camshafts were refitted, ensuring that the first one was rotated to the correct timing position before the second one was fitted. If the cams are fitted in the incorrect position, this can allow the inlet and exhaust valves to collide. Next job was to fit the cam bearing caps and these were then tensioned to the correct figure before the manifold studs were screwed into the head.
A threaded stud driver and hand speed brace were used for this operation, although I could have used a power tool. However, I prefer the speed brace as it allows a much better feel and reduces the risk of damaging a thread in the soft aluminium. Prior to refitting the head, the cylinder block studs were replaced. One or two of the old studs had some rust damage, so I purchased a replacement set from David Manners. On the original stud design the longer front left-hand stud for attaching the enginelifting bracket had a dowel section at the base to ensure accurate positioning of the head. All four of the longer studs in the new set were of the same design but came with a thin sleeve to slide over the dowel stud to perform a similar function. Prior to refitting the head, each stud was given a liberal coating of anti-seize to act as a rust preservative.
After placing the new head gasket onto the block, the engine crane was used to lift the head in position and once in place all the washers and nuts were fitted. I followed what it states in the manual and all the nuts were gradually tightened in the order shown and finally tensioned with a torque wrench. After the crank had been rotated to top dead centre and the two cams checked to make sure they were in correct position, the front chain sprockets were attached to the crank. The inlet one is retarded by one tooth on the adjustment plate, so a socket was used on the front of the crank to rotate the engine for a second check of the valve timing before a length of locking wire was fitted to the chain sprocket bolts.
A special tool was then used for finally adjusting the tension on the top chain and the cam cover gaskets were then glued to the head using a RTV sealant to keep them in place whilst the cam covers are fitted.
I prefer not to use this sealant between the cam covers and the gasket, as it can make future cover removal difficult. If oil does leak from the cam covers and becomes an issue, I can always remove the covers and seal them with RTV at a later date.
These valve seals are probably not a necessity on my E-Type’s engine, as it had new guides fitted at the last rebuild, but old habits die hard
Checking the clearance between the camshaft and tappet with the head sitting on blocks, as the valves open beyond the head face. Note the fixture on front of the camshaft to make rotation easy. New rubber oil stem seals were fitted to all the inlet valve stems.
Prior to replacing the E-Type’s cylinder head, the camshaft bearing cap studs were tensioned to recommended value. One of the old head studs had corroded badly so all were replaced. The new set didn't have a long stud with larger diameter dowel section at the base for correct head location but a sleeve had been supplied to provide a similar function. A special tool is required to tension the top cam chai on the XK engine. Note the locking wire fitted to top cam sprocket mounting bolts.