XJ12 5.3 1979 valve clearence
 

Hello, some can help me find a description of how to check valve clearence and put adapted shims. Thanks.

OK, 3 coffee's down.

Is the engine in one piece, or are the manifolds etc off it????

The rather testy chain tentioner needs to be locked in the rest position to remove the camshafts, and that sucker does snap very easily.

Motor is complete. I have no special tools. Or is there a way around?

Bugga.

The inlets need to come off, the camcovers come off.

The clearances can then be measured and written down. With 0.012" for the Inlet, and 0.014" for the Exhaust, are the spec, but on a preHE in used condition, 0.002" either way would be acceptable to me, due to the amount of work involved to correct any outside spec readings.

To rectify any oddities, the timing chain boomerang tentioner needs to be retracted and locked in that position. If this thing is old, and most are, it will 98% snap at the lower pivot, and 75% snap midsection, and you will hear it, as will we hear the words muttered.

Once that is dealt with, the cam sprockets can be undone and lifted to the steel support arms in place just for that purpose, then the camshafts cam be lifted, and shims replaced as needed to satisfy whatever.

Some have left that tentioner alone, and simply levered the sprockets to those arms, with the tentioner still holding that chain tight, and have had success. I have not had success with that method, as I have always heard that "click" as the tentioner ratchets outward, and the sprockets will not fit back on the snout of the camshafts without releasing that ratchet, so back to the previous paragraph.

There is NO workaround that I know of.

Our PreHE was always "tappety", and now at 540000kms, who cares, and I am NOT opening that engine for any reason.

thanks for info Grant. My technical Englishis not that good...
How do you lock that tentioner?
What do you mean by "snap"? Will this change the 'correct' valve timing. How can I check the valve timing while I am so far.

OK, understood.

The snaps attached show a broken tensioner, the whole thing, the tool used to PULL the thing into the retracted position.

Attachment 200511

Broken tensioner.

Attachment 200512

Same broken unit with the pivot hole intact, and that is the section I have mostly had snap off due to the HUGE pull needed to retract this unit.

Attachment 200513

The tool needed to retract the tensioner. Some have done with all sorts of handy stuff, wooden wedges, etc, but this is the Jaguar tool.

I have never used one.

If the tensioner is broken, sometimes there is a "ticking" noise heard, much like an Injector ticking, but low down at the RH front. Other times the engine hunts very slightly at about 1200 rpm, and sometimes at idle, and is very hard to pick if you are not real familiar with this engine.

The only check of the chain, and the general set up is the set the engine on TDC #1A Compression stroke. Use the setting plates in the slots in each camshaft to ensure the crank and camshafts are in time. A broken tensioner will show them as out of time, and mainly the RH shaft if the tensioner is broken, BUT, the stretch of the chain will also show the LH camshaft out of time, so it can be very confusing.

This is the cam timing plate I am refering to.

Attachment 200510

Thanks you so much. Although here the links are all broken (I informed the admin), its start to be clearer!! Guess links will be repaired in a few days
Greetings

PM me your email address, and I will send them direct.