Camshaft removal
#1
10-14-2012, 02:26 AM
Camshaft removal
I got the valve cover off on the exhaust side and expected to find some raised and most likely damaged tappet guides considering the tapping noise, no stake down kit and over 170K miles on the clock.
I was surprised to see that everything was in order, all tappet guides nicely seated and no damage to any of them. I guess the noise I'm hearing has more to do with increased valve clearance due to wear than anything else.
That means I will need to check the valve clearances and most likely remove the camshafts to get at the tappet spacers if need be.
I read a little bit about camshaft removal in the service manual and didn't understand the need for the special tool mentioned there. I wonder if there is a write somewhere that simplifies this task. For instance, if I only need to change the clearance for cylinder 1 (furthest from the timing chain) can't I just remove the cam holders and tilt up the cam at cylinder one to get at the spacers without having to undo the timing gear/cam bolts at the opposite end of the camshaft?
Also, what about the spacers? Should I order a handful at various thicknesses and estimate the correct one based on the measured clearance while the engine is cold?
I'm sure there is more involved than my current understanding but I wanted to gather a little more knowledge from the experienced ones before before I get into this.
I was surprised to see that everything was in order, all tappet guides nicely seated and no damage to any of them. I guess the noise I'm hearing has more to do with increased valve clearance due to wear than anything else.
That means I will need to check the valve clearances and most likely remove the camshafts to get at the tappet spacers if need be.
I read a little bit about camshaft removal in the service manual and didn't understand the need for the special tool mentioned there. I wonder if there is a write somewhere that simplifies this task. For instance, if I only need to change the clearance for cylinder 1 (furthest from the timing chain) can't I just remove the cam holders and tilt up the cam at cylinder one to get at the spacers without having to undo the timing gear/cam bolts at the opposite end of the camshaft?
Also, what about the spacers? Should I order a handful at various thicknesses and estimate the correct one based on the measured clearance while the engine is cold?
I'm sure there is more involved than my current understanding but I wanted to gather a little more knowledge from the experienced ones before before I get into this.
#2
10-14-2012, 05:47 AM
OK, not a 5 minute job by any stretch of any imagination.
The cam shaft/s MUST come off.
The top chain will require to be released via the vent housing at the front of the cylinder head.
The timing tool is required (my opinion) to set and hold the camshaft correctly when reattaching, so as not to damage valves by mis-timing the camshaft. It is also needed to set TDC prior to removal of the camshaft.
BEFORE DOING ANY OF THIS READ BELOW FIRST
Rotate the engine by hand (CLOCKWISE ONLY PLEASE) and measure ALL the tappet clearances you now have, WRITE THEM DOWN in cylinder order.
Once the camshaft is off remove the "buckets" using a magnet on a stick, one at a time, and measure the shim inside each bucket, write it down at the corresponding clearance you got previously. Now you can calculate the shim required to give the clearance you desire.
It usually takes me all day to this adjustment, it is time consuming, and if you get it wrong you still got noise, or teh clearances are too tight, which will bite you in some future time zone.
They do not usually wear, and I have dealt with tooooo many. Cracked buckets, bucket guides raising and dropping (without clobbering the camshaft), wrongly set by some fool erlier in life, are ALL what I have come across.
Broken inner valve springs on 2 in 40 years, so not on any real radar??.
Valve stem ends machined toooooo far down, so the shim actually sits on the collet keeper, have been way too common also. That can lead to a dropped valve if not corrected, but that does require the head to come off.
The cam shaft/s MUST come off.
The top chain will require to be released via the vent housing at the front of the cylinder head.
The timing tool is required (my opinion) to set and hold the camshaft correctly when reattaching, so as not to damage valves by mis-timing the camshaft. It is also needed to set TDC prior to removal of the camshaft.
BEFORE DOING ANY OF THIS READ BELOW FIRST
Rotate the engine by hand (CLOCKWISE ONLY PLEASE) and measure ALL the tappet clearances you now have, WRITE THEM DOWN in cylinder order.
Once the camshaft is off remove the "buckets" using a magnet on a stick, one at a time, and measure the shim inside each bucket, write it down at the corresponding clearance you got previously. Now you can calculate the shim required to give the clearance you desire.
It usually takes me all day to this adjustment, it is time consuming, and if you get it wrong you still got noise, or teh clearances are too tight, which will bite you in some future time zone.
They do not usually wear, and I have dealt with tooooo many. Cracked buckets, bucket guides raising and dropping (without clobbering the camshaft), wrongly set by some fool erlier in life, are ALL what I have come across.
Broken inner valve springs on 2 in 40 years, so not on any real radar??.
Valve stem ends machined toooooo far down, so the shim actually sits on the collet keeper, have been way too common also. That can lead to a dropped valve if not corrected, but that does require the head to come off.
#3
10-14-2012, 06:58 AM
Veteran Member
+1 on everything Grant says.
One thing to be REALLY obsessive about is to set up some absolutely solid numbered container to put the buckets and shims in unless you take Grant's advice and do one at a time, take it out, measure, re-shim and put it back.
DO NOT use an eggbox unless you've got a concrete one otherwise a puff of wind and flump, big trouble.
Yes, I did. Not with this engine and a long time ago but the scars are still there.
One thing to be REALLY obsessive about is to set up some absolutely solid numbered container to put the buckets and shims in unless you take Grant's advice and do one at a time, take it out, measure, re-shim and put it back.
DO NOT use an eggbox unless you've got a concrete one otherwise a puff of wind and flump, big trouble.
Yes, I did. Not with this engine and a long time ago but the scars are still there.
#4
10-14-2012, 01:33 PM
Thanks for the words of wisdom. Sounds like I definitely need the cam alignment tool.
Once I get the breather off, I don't have a good feel for what's involved to release the tensioner on the cam chains? Is the tensioner something that should be replaced on a high mileage motor? If so, I might consider getting a new one while I'm at it.
The motor has had many unknown mechanics work on it and judging by its condition, I'll bet some of them were not familiar with the XK6 or even Jaguar so it's hard to tell what I will find. I'll start by making the clearance measurements to see what I am up against.
Did I understand that the shims nor the tops of the buckets wear out? I assumed wear in these areas would account for increased gap and hence the noise. Also, it would mean replacing the worn parts would be prudent to get an accurate clearance measurement, but that's not what has been conveyed.
Instead it sounds like I'm more likely to find a broken shim, incorrect shim or improperly machined valve stem and also, I should put all the buckets and shims back onto the same valve that I pulled them from except where a new shim is needed.
Speaking of shims, since I don't have any spares on hand, I guess I will need to order new ones based on the clearance measurements I make and shim thickness I find under the bucket. Are there standard sizes available or do I need to order these custom made from a machine shop?
Once I get the breather off, I don't have a good feel for what's involved to release the tensioner on the cam chains? Is the tensioner something that should be replaced on a high mileage motor? If so, I might consider getting a new one while I'm at it.
The motor has had many unknown mechanics work on it and judging by its condition, I'll bet some of them were not familiar with the XK6 or even Jaguar so it's hard to tell what I will find. I'll start by making the clearance measurements to see what I am up against.
Did I understand that the shims nor the tops of the buckets wear out? I assumed wear in these areas would account for increased gap and hence the noise. Also, it would mean replacing the worn parts would be prudent to get an accurate clearance measurement, but that's not what has been conveyed.
Instead it sounds like I'm more likely to find a broken shim, incorrect shim or improperly machined valve stem and also, I should put all the buckets and shims back onto the same valve that I pulled them from except where a new shim is needed.
Speaking of shims, since I don't have any spares on hand, I guess I will need to order new ones based on the clearance measurements I make and shim thickness I find under the bucket. Are there standard sizes available or do I need to order these custom made from a machine shop?
#5
10-14-2012, 01:35 PM
Veteran Member
+1 on the above replies.
This is not a quick job, and you need to be prepared to spend all day on it, and sometimes the following, (or another), day if you have no spare bucket shims. This is because you don't know what shims to buy until you have taken it all apart, and you then have to buy the ones you need.
For each bucket, you have to put the correct thickness shim back in based on arithmetic from gap you find, and existing shim thickness on that valve and the gap needed. Generally speaking, the shims get thinner over time as the valve seats wear. You also need a good micrometer in Imperial, not Metric, to measure the existing shims; new ones have a letter etched on but this soon disappears when the engine runs.
This is not a quick job, and you need to be prepared to spend all day on it, and sometimes the following, (or another), day if you have no spare bucket shims. This is because you don't know what shims to buy until you have taken it all apart, and you then have to buy the ones you need.
For each bucket, you have to put the correct thickness shim back in based on arithmetic from gap you find, and existing shim thickness on that valve and the gap needed. Generally speaking, the shims get thinner over time as the valve seats wear. You also need a good micrometer in Imperial, not Metric, to measure the existing shims; new ones have a letter etched on but this soon disappears when the engine runs.
#6
10-14-2012, 06:40 PM
Thanks for the words of wisdom. Sounds like I definitely need the cam alignment tool.
Once I get the breather off, I don't have a good feel for what's involved to release the tensioner on the cam chains? Is the tensioner something that should be replaced on a high mileage motor? If so, I might consider getting a new one while I'm at it.
The motor has had many unknown mechanics work on it and judging by its condition, I'll bet some of them were not familiar with the XK6 or even Jaguar so it's hard to tell what I will find. I'll start by making the clearance measurements to see what I am up against.
Did I understand that the shims nor the tops of the buckets wear out? I assumed wear in these areas would account for increased gap and hence the noise. Also, it would mean replacing the worn parts would be prudent to get an accurate clearance measurement, but that's not what has been conveyed.
Instead it sounds like I'm more likely to find a broken shim, incorrect shim or improperly machined valve stem and also, I should put all the buckets and shims back onto the same valve that I pulled them from except where a new shim is needed.
Speaking of shims, since I don't have any spares on hand, I guess I will need to order new ones based on the clearance measurements I make and shim thickness I find under the bucket. Are there standard sizes available or do I need to order these custom made from a machine shop?
Once I get the breather off, I don't have a good feel for what's involved to release the tensioner on the cam chains? Is the tensioner something that should be replaced on a high mileage motor? If so, I might consider getting a new one while I'm at it.
The motor has had many unknown mechanics work on it and judging by its condition, I'll bet some of them were not familiar with the XK6 or even Jaguar so it's hard to tell what I will find. I'll start by making the clearance measurements to see what I am up against.
Did I understand that the shims nor the tops of the buckets wear out? I assumed wear in these areas would account for increased gap and hence the noise. Also, it would mean replacing the worn parts would be prudent to get an accurate clearance measurement, but that's not what has been conveyed.
Instead it sounds like I'm more likely to find a broken shim, incorrect shim or improperly machined valve stem and also, I should put all the buckets and shims back onto the same valve that I pulled them from except where a new shim is needed.
Speaking of shims, since I don't have any spares on hand, I guess I will need to order new ones based on the clearance measurements I make and shim thickness I find under the bucket. Are there standard sizes available or do I need to order these custom made from a machine shop?
Yes, and if you can find the special Jag tool to release the front chain adjuster. It can be done without that tool, but is more fiddle.
Replacement, no. You will see a big nut, 3/4 from memory, loosen it about 1/2 turn (standard thread), and then look at about 11 o'clock (I think), you will see a plunger, push the plunger IN, and wind the serrated wheel to release the tension on the top chain. NOTHING will fly out and smack you.
Fun will be had.
OK, in the real world they do wear, but it is NOT a critical wear. that would also depend on the quality of oil used over all these years, and the service integrity of previous owners, much like "how long is a piece of string". Some wear is acceptable, but a bucket that is real "hollowed out" on the face must be replaced.
Broken shim, doubtful. Wrong thickness, more likely. Machined valve tip, maybe, but that would depend if the head has ever been rebuilt, and I understand that is an unknown. Buckets back in the same hole, YES.
The shims are a standard Jaguar spare part, and readily available.
Last edited by Grant Francis; 10-14-2012 at 06:55 PM.
#7
10-25-2012, 11:58 PM
It's been a few weeks since I had time to get back to the jag. I have the valve covers off and tonight I used a remove starter switch to roll the engine over to get the valve clearances. Here's what I measured (cylinder 1 is at the back of the engine)
exhaust ---->0.013--0.012--0.011--0.012--0.013--0.011
Cylinder----->--1------2------3-------4------5-----6--
intake ------>0.012--0.010--0.013--0.013--0.011--0.009
I'm a little puzzled by the results. If anything I expected the gaps to be larger than the desire 0.012-0.014 range because of wear. Instead five of the gaps are actually tighter than they should be and none of the gaps were too big.
I guess I'll be looking for smaller shims rather than larger ones. Seven of the twelve valves have gaps within the desired range. Should I leave them as is or should make the effort to set them all at 0.013 in the hopes of getting the smoothest running motor?
exhaust ---->0.013--0.012--0.011--0.012--0.013--0.011
Cylinder----->--1------2------3-------4------5-----6--
intake ------>0.012--0.010--0.013--0.013--0.011--0.009
I'm a little puzzled by the results. If anything I expected the gaps to be larger than the desire 0.012-0.014 range because of wear. Instead five of the gaps are actually tighter than they should be and none of the gaps were too big.
I guess I'll be looking for smaller shims rather than larger ones. Seven of the twelve valves have gaps within the desired range. Should I leave them as is or should make the effort to set them all at 0.013 in the hopes of getting the smoothest running motor?
Last edited by e21pilot; 10-26-2012 at 12:03 AM.
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#8
10-26-2012, 04:38 AM
Maaaaaate, DONT RE-INVENT the wheel.
The ones that are toooooo tight need MORE attention than the slack ones.
# 2,3, 4, 6 exhaust need setting.
# 2, 6 Intake need setting.
When I do the whole set I use 0.013 Inlet, and 0.015 Exhaust. Every operators "feel" when measuring these will be different, so as long they are within 0.001 of spec, the engine will be fine.
MY OPINION ONLY HERE. But it has worked for me for a long time.
The ones that are toooooo tight need MORE attention than the slack ones.
# 2,3, 4, 6 exhaust need setting.
# 2, 6 Intake need setting.
When I do the whole set I use 0.013 Inlet, and 0.015 Exhaust. Every operators "feel" when measuring these will be different, so as long they are within 0.001 of spec, the engine will be fine.
MY OPINION ONLY HERE. But it has worked for me for a long time.
#9
10-26-2012, 03:21 PM
Grant: Based on your input, I will likely do them all at 0.013 intake and 0.015 exhaust.
Based on your experience, did you tend to see the clearances tighten up or open up after time. I thought they should loosen for sure but that doesn't see to be the case on my engine.
Also, do the shims typically wear out in the center or do they stay flat on the bottom? I have a set of calipers that are handy for measuring flat shims but if the wear is uneven, I may need to dig out the old micrometer to do the job.
Based on your experience, did you tend to see the clearances tighten up or open up after time. I thought they should loosen for sure but that doesn't see to be the case on my engine.
Also, do the shims typically wear out in the center or do they stay flat on the bottom? I have a set of calipers that are handy for measuring flat shims but if the wear is uneven, I may need to dig out the old micrometer to do the job.
#11
10-27-2012, 05:18 AM
The shims are "case hardened", or at least the bag I have are, but they are old new stock, like me.
They do get a "wear mark" on the side that contacts the valve stem. I measure with a micrometer (imperial) on the outer edge.
Swapping them around where you can does NO harm, and I do that all the time. Quite surprising sometimes how few new ones are actually needed.
My experience is the clearances close up, as the valve itself wears, but generally only a 0.001" or so, and that gives NO problems in my opinion.
They do get a "wear mark" on the side that contacts the valve stem. I measure with a micrometer (imperial) on the outer edge.
Swapping them around where you can does NO harm, and I do that all the time. Quite surprising sometimes how few new ones are actually needed.
My experience is the clearances close up, as the valve itself wears, but generally only a 0.001" or so, and that gives NO problems in my opinion.
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anjum (10-28-2012)
#12
10-27-2012, 05:25 AM
Just had a thought.
When you do the refit, after you have the desired shims installed, a check of the clearances is a MUST.
DO NOT, and I repeat DO NOT rotate one camshaft with the other camshaft installed, you WILL bend valves.
Either have one OFF when checking the opposite side, OR, re-attached the sprockets and rotate the engine BY HAND, NOT the starter motor, to complete the check. Sometimes more than one shim rehash is required to get them all as you want them.
When you do the refit, after you have the desired shims installed, a check of the clearances is a MUST.
DO NOT, and I repeat DO NOT rotate one camshaft with the other camshaft installed, you WILL bend valves.
Either have one OFF when checking the opposite side, OR, re-attached the sprockets and rotate the engine BY HAND, NOT the starter motor, to complete the check. Sometimes more than one shim rehash is required to get them all as you want them.
#14
10-28-2012, 12:12 AM
Just an update guys,
I got both cams of last night and have all the removed parts sitting on the concrete so there's no way I will swap cams by mistake!
I did observe that the centers of the buckets are somewhat polished from contact with cam but not hollowed out. Both the buckets and cam seem in excellent shape with no unexpected surface markings.
I've dug out the old imperial units Mitutoyo micrometer with Vernier scale for measuring the shim thickness right in the center area. I'll be making the measurements hopefully tomorrow and then ordering the shims I need. I wonder if I should pickup used shims instead of new ones? Lots of new parts these days are made of questionable quality. I'm not even sure the Jaguar dealer makes these shims anymore.
Since I'm a newbie at the procedure, I will test fit the cams (one at a time) and re-measure the clearances just to check my work.
Thinking ahead to re-assembly, should I replace the timing sprocket/cam bolts as well as the bendable locking plates or just try to re-use the ones I have?
Lastly, I have to confess I could not find an practical way to rotate the engine by hand. There was so much stuff in the way (US model) that I could not get a 1/2" drive socket and wrench combo on the crank to do it.
Instead, I pulled the plugs and used the remote starter switch to kick the engine over to whatever position I wanted. I made sure to disconnect the switch and battery while I have the cams off so there is no way the engine will rotate. When I will test fit the cams, I will rotate them manually to make the clearance measurements.
I got both cams of last night and have all the removed parts sitting on the concrete so there's no way I will swap cams by mistake!
I did observe that the centers of the buckets are somewhat polished from contact with cam but not hollowed out. Both the buckets and cam seem in excellent shape with no unexpected surface markings.
I've dug out the old imperial units Mitutoyo micrometer with Vernier scale for measuring the shim thickness right in the center area. I'll be making the measurements hopefully tomorrow and then ordering the shims I need. I wonder if I should pickup used shims instead of new ones? Lots of new parts these days are made of questionable quality. I'm not even sure the Jaguar dealer makes these shims anymore.
Since I'm a newbie at the procedure, I will test fit the cams (one at a time) and re-measure the clearances just to check my work.
Thinking ahead to re-assembly, should I replace the timing sprocket/cam bolts as well as the bendable locking plates or just try to re-use the ones I have?
Lastly, I have to confess I could not find an practical way to rotate the engine by hand. There was so much stuff in the way (US model) that I could not get a 1/2" drive socket and wrench combo on the crank to do it.
Instead, I pulled the plugs and used the remote starter switch to kick the engine over to whatever position I wanted. I made sure to disconnect the switch and battery while I have the cams off so there is no way the engine will rotate. When I will test fit the cams, I will rotate them manually to make the clearance measurements.
#16
10-28-2012, 03:47 AM
FWIW when there's a rocker the clearances tend to increase with time as the rocker components wear.
With 'direct drive' as the valve sits into the seat the clearances, as Grant says, tend to reduce.
Grant will correct me but I don't think these clearances will account for your noise.
With 'direct drive' as the valve sits into the seat the clearances, as Grant says, tend to reduce.
Grant will correct me but I don't think these clearances will account for your noise.
I dont think those clearances would create anything audible to the human ear.
A bucket guide moving in the head is more likely if a noise is present in this area, and it MAY NOT be obvious.
I would strongly suggest a stake down kit be fitted, get a brass punch, with a BIG hammer, and smack each guide to ensure it is "home" correctly.
#17
10-28-2012, 03:52 AM
As Steve said, NEW lock tabs, the rest is just fine. I also put ONE drop of loctite on the threads of each bolt at final assembly, just because.
I have seen one where a bolt came out, NOT PRETTY.
When you retighten the top chain, DO NOT tighten it too much, or you will get a "chain whir". I take it up firm/tight, then back off the serrated wheel 1 tooth, all good.
I have seen one where a bolt came out, NOT PRETTY.
When you retighten the top chain, DO NOT tighten it too much, or you will get a "chain whir". I take it up firm/tight, then back off the serrated wheel 1 tooth, all good.
#18
10-30-2012, 02:54 AM
Just a quick update, I pulled all the buckets and shims and made the measurements. I'm going to re-use 4 of them and I order 8 new ones that should be here in a few days.
Only thing of interest I noticed was that two of shims were roughed up with what was probably emery cloth. I guess a previous mechanic was short on shims and tried to take off .001 or so to get the shim he wanted but it didn't seem to work from my measurements. I'll be replacing these shims for sure.
Looking forward to getting the cams back on!
Only thing of interest I noticed was that two of shims were roughed up with what was probably emery cloth. I guess a previous mechanic was short on shims and tried to take off .001 or so to get the shim he wanted but it didn't seem to work from my measurements. I'll be replacing these shims for sure.
Looking forward to getting the cams back on!
#19
10-30-2012, 07:11 AM
Veteran Member
#20
11-13-2012, 06:15 AM
I finally got time to put in the shims I ordered. Did the exhaust side first. Put in the new shims, installed the buckets and the cam. Rotated the exhaust cam to verify the 0.015 clearance across all six valves.
Removed the exhaust cam and then did the same steps on the intake side. When I went to verify the 0.013 clearances however, I found it difficult to rotate the intake cam when the valves on cylinders 1 and 6 where fully open. I then found clearances on cylinders 2-5 were 0.013 as expected but 1 and 6 were much larger than they should have been and I'm not sure why?
I'm wondering if the intake valves on 1 and 6 may have skimmed the top of the pistons and picked up some carbon build up on the valve edge that could account for the excess clearance I measured. If so, should I do about this?
Removed the exhaust cam and then did the same steps on the intake side. When I went to verify the 0.013 clearances however, I found it difficult to rotate the intake cam when the valves on cylinders 1 and 6 where fully open. I then found clearances on cylinders 2-5 were 0.013 as expected but 1 and 6 were much larger than they should have been and I'm not sure why?
I'm wondering if the intake valves on 1 and 6 may have skimmed the top of the pistons and picked up some carbon build up on the valve edge that could account for the excess clearance I measured. If so, should I do about this?