Jaguar Repair: vales, cam sprockets, shop rags

Question
how do i ajust vales on a 1987 jag 4.2 6 cyln.

Answer
Hi Howard,

First you need to check the valve clearance on both intake and exhaust valves with a feeler gauge by rotating the engine a little at a time until each cam lobe it pointed away from it's lifter. Then write down each clearance.

It is difficult if you don't have a valve shim assortment but it can be done. You will also need a micrometer of a good caliper to measure each valve shim.

Here is the procedure. First set the crankshaft at exactly TDC as per the timing mark on the front pulley. Then look at the notch in the cam flange close to the first cam bearing cap. If they are pointed out away from the head at a 90 degree from the cam cover gasket surface rotate the crank one time back up to TDC (Top Dead Center) and confirm that the notches are pointed inward toward the head.

Take a shop rag and stuff it down into the cam chain area just below the bolts that hold the cam sprockets to the cam. (so that you can't drop a bolt down into the cam chain area) Now with a small chisel or punch and hammer bend open the lock tab on the cam bolts that you can access and remove the bolts that you can reach. When you have removed the bolts accessible, remove the shop rags from both sides and rotate the crank again to TDC and this time the notches should face out away from the head at 90 degrees to the gasket surface of the cam cover.

Now stuff the shop rags back into the chain area and unlock the other tabs and remove the remaining bolts and locking plates. Now you can remove both shop rags and pry each sprocket off of each cam. Since you will not have the locking clips to fit the notch in the small center peg in the sprocket you can use safety wire to tie the sprockets so that they are away from the cam flanges.

WHAT EVER YOU DO BE CAREFUL NOT TO REMOVE THE LARGE WIRE CLIP IN SIDE THE EDGE OF THE SPROCKETS!!!!!

Now, note that each cam bearing cap has a number stamped on it next to a number stamped into the head. Each cam bearing cap MUST be kept with it's correct number position on the head.!!!

Remove every nut a little at the same time so as to let the cam up all the way down the head. You must not remove one cap at a time, they must all come up evenly. When they get up about half way the cam my suddenly flip over but that is normal and nothing to worry about. Don't get the cams mixed up.!!! Now you can lift each lifter out of it's bore but you MUST keep each lifter in order and they must not be mixed up.!!!

Under each lifter is a valve pad. Now each valve pad must be miked to see what thickness it is. Places each pad in order so that you know for sure which pad came out of what position on the head. You must write down the thickness next to each valve clearance that you measured with your feeler gauge.

For example, if you measured .016" with your feeler gauge and you know the clearance is suppose to be 12 to 14 thousandths and you valve pad measured .100" then you will need to replace that pad with a pad that is from 2 to 4 thousandths thicker. Best would be .003" thicker or a .103" thick pad. If you were careful with your measuring that would net you a new valve clearance of .013" which is ideal as the valve clearance is suppose to be between .012" and .014" .

I usually find that among all the pads there are several in other positions that match what I need so often if you need a .103" pad for a valve, you will find a .103" in another position that you can use. This usually makes it necessary to only need several new pads rather then all new pads. Also, some will not even need to be changed at all.

WHEN YOU ARE FINISHED AND READY TO PUT THE CAM BACK ON THE HEAD YOU MUST PLACE IT IN POSITION SO THAT THE NOTCH IS FACING AWAY FROM THE HEAD AND TO HOLD IT IN THAT POSITION WHILE EVENLY BOLTING DOWN THE CAM BEARING CAPS I FOUND IT EASY TO HOLD THE CAM IN POSITION WITH A PAIR OF VICE GRIP PLIERS ON THE CAM SHAFT.

YOU CAN NOT!!! BOLT THE CAM IN PLACE AND THEN ROTATE IT INTO THE CORRECT POSITION, IT MUST BE HELD IN THE CORRECT TIMING POSITION AS IT IS BOLTED IN PLACE.!!!!

KEEP IN MIND THAT IF YOU DO NOT WRITE DOWN EACH CLEARANCE AND KEEP EACH LIFTER AND PAD IN IT'S CORRECT POSITION IT IS A DISASTER!! TO EVEN AN EXPERIENCED JAGUAR MECHANIC.

The valve pads are available from any Jaguar dealer or any of the many On-line Jaguar parts houses. Like Engel Imports.

Howard