Tuesday, 17 April 2012


Assembling the timing gear and fitting to the engine block

I may be unlucky, but with a couple of notable exceptions, the general quality of 'repro' parts I've had delivered from UK suppliers leaves a good deal to be desired.  I guess to some extent it has always been so, with constant downward pressure on prices limiting what can be achieved in quality.  Could it be that quality is considered less important for vehicles that typically cover small annual mileages.  Failure for example, of a relatively insignificant engine part can have disastrous and very expensive consequences, but the passage of time means that we we are less likely to hold the culprits to account.  I've dealt with most of the purveyors of classic car parts over the years, and I suspect that many have quite a few suppliers in common.  Imported parts from the Far East, India and China have garnered a reputation for poor quality, but I am told that many Jaguar repro parts are manufactured around the Coventry area by ex employees of the once Great British motor industry (could there be a clue here?).  Conversely, parts purchased  from the USA have been flawless. 

Surely it would be better to pay a little more, then spend a good deal less time checking and fettling facsimile parts to make them good for purpose. 
So what has brought about this 'rant'.
I required new chains, guides and a tensioner conversion for my engine rebuild. Result:

The chains supplied have arrows on the links indicating I suppose the direction of travel (why else would they be there?) but every few links they randomly change direction.  This and the split link arrangement left me feeling decidedly uncomfortable.  After some deliberation, I bought another pair, original Reynolds for the top and a split link free repro (no originals available) for the bottom.

The bottom chain guide was around 10 degrees off being at right angles to it's mounting base, meaning if not 'adjusted' the chain would have worn the guide away on the inside first.

The top chain guides, combined with the spacers supplied are around 1mm less deep than the original brass items (1.125") which means the aluminium castings they are sandwiched between could be bent / stressed.  Also the rubber face sits around 125 thou higher than the original.  Whilst easily remedied, is this intentional, and better than the original, or an error.  How do I find out? 

New and old upper chain guides.  Unusually, a post on Jag lovers
forum asking what might be used to replace the original worn nylon
type material on the lovely brass casting drew a complete blank.
Have I inadvertently upset the usual sages. 

New upper guides are 35 thou less deep (should be 1.125")
Does it matter?  I'd love to know !

New upper guides are also around 0.125" higher than originals.
Is this an improved design or just a mistake.
Again, I would really like to know.
The hydraulic conversion kit brass mounting block required a good deal of relieving to allow it to fit, not really a problem, but when the hydraulic bit was installed, it was tight up against its back stop and still exerting excessive pressure on the chain.  I would guess the rubber pad's life would not be long (but possibly a couple of years for a low mileage classic). 
The tensioner conversion takes its oil from the feed originally used for an oil spray bar, which is dispensed with, so no more oil for the crankshaft sprocket and distributor drive gear.  I guess this must be OK but it would be good to know for certain.

Brass mounting block needed quite a bit taking off to make it fit.
Is this peculiar to my engine or all engines ?

All of the above issues are to some extent sorted.  As an amateur restorer my time is effectively free but I wouldn't like to be footing the bill from a professional for all this additional remedial work.

So - having got that off my chest, back to the engine build.   I have a couple of books that helped enormously, each with its own slant on the processes involved. 

JEC publication - 'On Jaguar XK120 Restoration' - ISBN 1 873098 38 1
A fairly comprehensive 120 restoration guide with some good detail pics.

Excellent and well known Dave Pollard book  'Jaguar XK Engine'
ISBN 1 85960 007 7   Don't start work without it.
Both books mainly relate to later XK engines, so I am not sure if my very early engine has some minor differences, sometimes requiring a slightly different approach.  In summary, this seems to be the preferred procedure and it mostly worked for me:

First - assemble rear plate - Graphogen on all moving parts

Next fit the front plate and adjuster mechanism.
Note marks on serrated wheel probably due to attempts
to adjust with incorrect tool.  Fortunately no real damage.

then - hang  the assembly from crank sprocket
(Engine upside down)

Fit assembly.  Note - lower guide in place - parallel in both plains
to chain but not quite touching.

Finally fit Hydraulic tensioner conversion.  Note how the rubber foot
is totally back in it's housing.  Chain tension is just acceptable after
enlarging all tensioner assembly holes to allow it to move around
1.5mm to left.
Some points not mentioned in either book:
Double check and measure every repro part for quality, dimensions etc. against your original parts and remember to grumble at your supplier if you need to tweak them.  They might eventually start to get the message.
If you fit the hydraulic chain tensioner
Install the bottom chain on its intermediate sprocket before you finally fit it's shaft in place and secure with a circlip.  (my none split link chain wouldn't quite go on with the sprocket fitted first)

This part of the engine build has taken quite a bit longer than I had planned and was not particularly enjoyable, so it's time for a little light relief. 
The body shop were never really happy with the boot lid, so I plan to make a new wood frame and fit it with a good skin, but this first needs to remove from yet another lid I found locally.  Next post showing this to completion (hopefully) will be at the beginning of May.