Jaguar head case sorted

Classics Monthly - - Driver’sdiary -

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.

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