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Jaguar XJ12 SI
Restoration
Engine
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Engine Block
Seeing this dinosaur sitting on my mechanic's work bench filled me with apprehension, I mean, this is not exactly an ideal engine for a beginner starting to learn the trade.
But there was no need to worry, it is a pretty straight forward engine, with a fairly simple design (albeit huge) and quite a few modern features, very well thought out for servicing and tune. The problem always with these engines is the restricted access, and the extra complication provided by emissions laws. The XJ12 has the dubious honour as the first UK needing EGR - Emission Control system in the domestic market plus Air Conditioning, Power Steering etc.
It took me over a week of solid work to clean the block with a very powerful detergent (my hands' skin knows all about it, use always extra strong gloves). I do not trust sand blasting or any other solid media as grit can engrain itself in the most obscure crannies and create mechanical havoc later on.
Once cleaned, all components were examined very closely; crank had virtually no measurable wear, no marks, nothing, this is astonishing! But then, this a high quality item forged in Molybdenum EN16T Steel, tuftrided for extra strength and wear resistance.
The Epicyclic oil pump (similar as found in automatic gearboxes) again was as new, its position was duly noted for later re-assembly.
I did go to the trouble of measuring the weight in all piston/rings/pins./rods assembly and found a maximum difference of 12 grammas between the lightest and the heaviest. I certainly was keen in balancing the weights, judiciously removing extra material along the forging marks on the rods. Unfortunately I did not have access to shot peening process in order to re-establish rods surface strength. Much to my chagrin, I assembled as per original condition.
I took measures to never to mismatch these piston/rod assemblies or any other reciprocating components, always keeping in separate plastic compartments. This is due to specific wear patterns that develop between inter acting parts that can be accelerated if there's a mismatch between parts of different assemblies. I made sure never to mix any part by writing down each part reference or casting number in my agenda as you can always find a particular mark in each component, otherwise we can always lightly engrave, as I did with the cylinder liners, marking 1A, 2A...6B.
But there was no need to worry, it is a pretty straight forward engine, with a fairly simple design (albeit huge) and quite a few modern features, very well thought out for servicing and tune. The problem always with these engines is the restricted access, and the extra complication provided by emissions laws. The XJ12 has the dubious honour as the first UK needing EGR - Emission Control system in the domestic market plus Air Conditioning, Power Steering etc.
It took me over a week of solid work to clean the block with a very powerful detergent (my hands' skin knows all about it, use always extra strong gloves). I do not trust sand blasting or any other solid media as grit can engrain itself in the most obscure crannies and create mechanical havoc later on.
Once cleaned, all components were examined very closely; crank had virtually no measurable wear, no marks, nothing, this is astonishing! But then, this a high quality item forged in Molybdenum EN16T Steel, tuftrided for extra strength and wear resistance.
The Epicyclic oil pump (similar as found in automatic gearboxes) again was as new, its position was duly noted for later re-assembly.
I did go to the trouble of measuring the weight in all piston/rings/pins./rods assembly and found a maximum difference of 12 grammas between the lightest and the heaviest. I certainly was keen in balancing the weights, judiciously removing extra material along the forging marks on the rods. Unfortunately I did not have access to shot peening process in order to re-establish rods surface strength. Much to my chagrin, I assembled as per original condition.
I took measures to never to mismatch these piston/rod assemblies or any other reciprocating components, always keeping in separate plastic compartments. This is due to specific wear patterns that develop between inter acting parts that can be accelerated if there's a mismatch between parts of different assemblies. I made sure never to mix any part by writing down each part reference or casting number in my agenda as you can always find a particular mark in each component, otherwise we can always lightly engrave, as I did with the cylinder liners, marking 1A, 2A...6B.
The corroded studs were a replaced with new supplied by SNG Barratt although other specialist and Jaguar itself will have it available at a fair price. To remove these studs can be a pain, I have used a stud extractor but if none is available, we can always use two nuts tightened against each other so it doesn't move and start to undo the stud by moving counter clockwise the lower nut (if right thread).
Slowly and reading Jaguar XJ12 Workshop manual, the engine started to take shape, one point of stress was not finding replacement side seals for rear crank seal cap. Apparently is no longer available and most specialist recommend to use your existing ones with a dab of black silicon or if yours are broken, just fill the cavities with high quality black silicon. I did clean mine and used black silicon, still no leaks ... yet.
New crank caps (STD) were added as I marvelled at the engine's engineering beauty . The block extends well bellow the crank line and has strengthening ribs all along its length, where it meets the crank mains that secure the crank with four stud cap each (seven of them) giving it the necessary torsion rigidity for such long all alloy engine. One peculiar feature is the alloy heads which are a major contribution for these engines rigidity as these blocks were produced in alloy to save some weight. This is not really a surprise as Wally Hassan and Harry Mund were renowned Formula 1 engine designers; among other mechanical jewels such as Coventry Climax and BRM engines.
As I did not have access to a crank rear sizing tool so I followed Chris Coleman and Jorge Maia's advice and use the crank itself to slowly seat the seal in place. This was accomplished by turning the crank and slowly tightening the last main cap, then withdrawing and removing the seal excess material and repeating this operation until seal was firmly in place, sized and trimmed to perfection. Tight but no too much, still enabling the crank to turn freely without the risk of overheat at later date.
Fidanza alloy flywheel was installed (don't mind the zinc plated bolts, there just for the pic, proper Jaguar hardened ones were fitted), much lighter than original E type V12 I got with the box (thanks Jim!). It offers much quicker response from the engine. Stainless steel 304 grade manifolds were fabricated by my father, using 38mm primary pipes and 44 secondaries, unfortunately, due to space available, it was impossible to do equal lenght primaries, but nevertheless, it is a big improvement over the restrictive cast iron originals (block hugger type).
Fortunately, all components were still witthin factory tolerances, with no measurable wear, so STD crank main and rod big ends caps were duly fitted along with new tensile conrod bolts. Next, the heads, pass the grinder...
Slowly and reading Jaguar XJ12 Workshop manual, the engine started to take shape, one point of stress was not finding replacement side seals for rear crank seal cap. Apparently is no longer available and most specialist recommend to use your existing ones with a dab of black silicon or if yours are broken, just fill the cavities with high quality black silicon. I did clean mine and used black silicon, still no leaks ... yet.
New crank caps (STD) were added as I marvelled at the engine's engineering beauty . The block extends well bellow the crank line and has strengthening ribs all along its length, where it meets the crank mains that secure the crank with four stud cap each (seven of them) giving it the necessary torsion rigidity for such long all alloy engine. One peculiar feature is the alloy heads which are a major contribution for these engines rigidity as these blocks were produced in alloy to save some weight. This is not really a surprise as Wally Hassan and Harry Mund were renowned Formula 1 engine designers; among other mechanical jewels such as Coventry Climax and BRM engines.
As I did not have access to a crank rear sizing tool so I followed Chris Coleman and Jorge Maia's advice and use the crank itself to slowly seat the seal in place. This was accomplished by turning the crank and slowly tightening the last main cap, then withdrawing and removing the seal excess material and repeating this operation until seal was firmly in place, sized and trimmed to perfection. Tight but no too much, still enabling the crank to turn freely without the risk of overheat at later date.
Fidanza alloy flywheel was installed (don't mind the zinc plated bolts, there just for the pic, proper Jaguar hardened ones were fitted), much lighter than original E type V12 I got with the box (thanks Jim!). It offers much quicker response from the engine. Stainless steel 304 grade manifolds were fabricated by my father, using 38mm primary pipes and 44 secondaries, unfortunately, due to space available, it was impossible to do equal lenght primaries, but nevertheless, it is a big improvement over the restrictive cast iron originals (block hugger type).
Fortunately, all components were still witthin factory tolerances, with no measurable wear, so STD crank main and rod big ends caps were duly fitted along with new tensile conrod bolts. Next, the heads, pass the grinder...
