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Conference terri::cars_uk

Title:Cars in the UK
Notice:Please read new conference charter 1.70
Moderator:COMICS::SHELLEYELD
Created:Sun Mar 06 1994
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2584
Total number of notes:63384

1505.0. "BIG problem with a 74 JAG XJ12L V12 engine! HELP!" by SENIOR::PAREDES () Tue Jul 16 1991 20:39

    I have a BIG problem with my 1974 Jaguar XJ12L!
    
    The timing chain tensioner broke while the car was idling in my
    driveway.  Tensioner pieces pierced the right side valve cover.
    
    I decided to replace the tensioner and chain which means pulling the
    heads. (I'm not a mechanic, I got lots of help.)  We discovered that
    I have a broken valve seat. We found pieces of valve seat in the
    intakes of the carbs.
    
    At this point I'm super frustrated!  Currently I'm in the HATE mode of
    my LOVE/HATE relationship with this automobile.  If this was any other
    car it would be HISTORY by now.
    
    Should I try to rebuild this V12 engine which has almost 80,000 miles
    on it or get another engine?
    
    I'm shopping for an engine now.
    
    Does anybody have experience with this level of repair or problem?
    
    This is my first Jag. I don't want it to be my last.
    
    Thanks for any help offered.
    
    Juan Paredes
    Nashua, NH 
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1505.1Rebuild it!DCOPST::BRIANH::NAYLORTigers fly, Spiders roar!Tue Jul 16 1991 22:2711
The V12 engine is a delight to work on as far as total rebuild is concerned.
I assume you have a degree in plumbing, too, right? :^)  While you're at it,
put in the more modern fuel injection system if you can spare the cash.

Basically, it is a simple engine, there's just rather a lot of it :-)  There
are some procedures to be very careful of, and replacing the timing and cam
drives is one of them!  Contact the Jaguar Driver's Club in Luton (if you're
not already a member) as they are incredibly helpful to anyone tackling this
type of work.

Enjoy yourself, and the car!	Brian
1505.2A few points.TIZER::WILSONWed Jul 17 1991 10:0435
    The Jag engine should be good for 130k miles, so I'd have no doubt
    about setting right, your 80k engine.
    
    It may be worth "shopping" around for a top end (head, valve gear, etc).
    
    Basically, the top end rebuild is not too difficult. What you MUST
    ensure though, is that you set up the valve timimg correctly, FIRST
    time, otherwise you will end up with yet more problems. Some cars are
    forgiving if you miss align the valve timing, but the Jag, Mercedes and
    Audi range eg, certainly are not. There have been many good re-builds 
    totally let down at this stage. If the timing is out by one tooth, then 
    BANG goes all the work.......I know, for I was that man once!!!!
    
    The head of the Jag is prone to warping, and corrosion within the water
    jacket sections of the head, before fitting any head, have it checked
    for these two common faults. As far as I remember, you can take up to
    12 thou/inch off the head before problems start to arise.
    
    If and when you tackle this job, take care to clean "with petrol" the oil 
    galleries, on the head. Shimming up the valve clearences is also a
    major task which should be done with the utmost care. 
    
    Jaguar got into the alloy component business rather too quickly. Be
    very careful when securing studs/bolts into these alloy components.
    They have a very low tolerence to force, and tend to strip VERY easily.
    Also, I suggest you do some weight training before opening the tool
    box, for just about everything on the Jag is heavy!! 
    
    Don't be kidded, this is a BIG job requiring a fair degree of
    knowledge, if it is to be done right. Jaguar engines really need to be
    well looked after, or they will soon let you know about it.
    
    Sorry to hear about your let-down, good luck.
    
    John.