Well, I feel like a total idiot right now. I got the tensioners, needed to special order the bolts. Got the first tensioner in without messing the timing up. Started to re-attach the cam shaft and was having a heck of a time with it. Long story short, where would be a good place to find a passenger side exhaust cam shaft...

 

you need more info, cause you cannot just slap another cam in. You have to set the clearances for each valve. The buckets to lobe clearance with shims under the buckets. So what did you do??

 

Camshaft broke in half... How difficult will it be to set the valve clearances? If its asinine, then she is a parts car. Sad to say it, but there are already plenty of other things that need attending to.

 

What part of the procedure caused the camshaft to break?

 

It occurred when I was reinstalling/re bolting the camshaft after replacing the secondary tensioners. I tried my best to even out the tension on it when bolting it back in. It was in an awkward position based on its timing, which made it difficult. The other cam did not have a problem going in at all. I heard a large bang and then saw a horrific sight.

 

Jagscott:
While you have indeed caused yourself some pain, the easiest fix is to put another head on. I bought a well used head on e-bay a few years ago for less than $100. It is running now. So, are you up to r/r the head?

If you do not want to r/r the head, or can't find a reasonably priced head, I would sure give an effort to setting the valve clearance with that head on the car. It is slow and tedious, but frankly it is a good exercise in tolerance calculation and it teaches you patience. I would worry about the cam bearing blocks. Are you sure you did not gouge any of the bearings when the event happened?

As to where to get the cam, which engine are we talking about? The AJ 26 has one trigger on the cps setup and the AJ-27 has four. If it is an AJ-26 and my cam has not succumbed to surface rust, I know where you can get one for shipping or so.

A couple of things are working in your favor. Many of these engines have Nikasil or bent piston issues, but few cylinder head issues. Ergo, the heads are mor available than the lower end in the scrapper market.

 

Thanks Ross for giving it to me straight. The head bearings were not gouged at all thankfully. Don't know if that helps things or not. I think the engine type is the AJ 26. Its a 1998, so it falls in that category. While taking off the tensioner, I noticed some water spray out one of the tensioner's bolts too. So it might be wise to take the head off and replace the gaskets too. Might as well, right? It will also give me a chance to look at the condition of the liners and then decide from there. I plan on keeping the car awhile, its in descent shape and was well looked after.

 

The head replacement is not trivial. Lots of other stuff involved. Can you provide more details about where you found the coolant? My extra cam looks pretty good and looking at some pictures, I believe that checking the lash might not be all than bad on the car. And I have some shims too.

 

The water came out of one of the tensioner bolt holes. It was under pressure and squirted out when the bolt broke free. It was very little water, didn't appear to be coolant.

 

Here are some pics of the disaster. Don't know if it helps. In one of the pictures, you can see a slight amount of damage done to the bearings. It really doesn't look like anything big. Its not deep and does feel smooth. Its more a scuff than a gouge.

Here she is. Now residing in my garage until I repair her. I plan on repainting her later. The interior is flawless though... The a/c vents are all intact, imagine that! No tears on the leather either. Overall, a well looked after Jag despite its outward appearance.


The broken camshaft up close

The scuff in the bearing made by the fracture. Its a very light scuff. I can't even feel it.


The broken cam after the feeble attempt of replacing only the secondary tensioners. I will be replacing the primaries, guides, and chains as well. Especially after this incident. For those of you who wonder "what could go wrong during this procedure" well, this is exactly what could happen . I tried my hardest to keep the tension even on each bearing, but alas. It happened... Most competent DIY mechanics (surely more competent than I) could do this procedure without too much difficulty. However, just know what you are getting yourself into before you DIY instead of having a professional do it!

 

So you used the 'tip the cam up' method, instead of the 'clamp the cams down and remove the sprocket' method, correct? Did you, perhaps, pull out the retainer pin on the upper tensioner before tightening down the cam bearings?

 

I am trying to understand this also.

It was my understanding that you worked on one bank - getting everything into the correct position -- whatever that is -- finishing that side and then moving and setting up the second bank in the same manner.


I guess I do not understand what happened. I used to rebuild old TR4's and 6's - bit different. British cars did not have tolerances back then

 

I bet your heart sank when you heard that crack!
IMHO it has to be easier to replace the cam and set up the clearances if you are confident that everything else is in good shape.
It sounds like sparkenzap may be able to help you out with the parts.

 

Scott:
I wonder if you had a cap backwards? That's why I asked about the gouge. I would think it fairly hard to snap a cam from simply tightening somewhat unbalanced.
BTW, what I have is an XJR cam. I am trying to determine if the NA cam is the same.

 

Yes, I used the "tip up the cam method" as you can see the lovely zip tie. The other bank is fine, in other words. The procedure is complete on the left bank and everything went smooth. I then started to work on the right bank, and while tightening the bearing caps back down, the damn thing broke. And you bet my heart sank! I did not remove the retainer clip prematurely either. I made sure to keep the bearing caps in the same order and orientation as they were before I removed them. What I think occurred, is the cam was in an unusual position based on its timing and lobe positions. One of the lobes towards the center was down I believe, which sort of teetered the cam in a "seesaw" fashion. Making it incredibly difficult to keep the tensions placed on the cam by the bearing caps even. The cam might have also bee weak. If the cam was weak, I am certainly glad it broke while I was working on it instead of on a Sunday drive. W/E the cause, the damn thing broke. Sparkenzap, I can't tell you how much your help means. Thank you!

 

A fellow I know just had his cam shaft break in the Cirrus SR 22 he was flying at night. Fortunately the CAPS (ballistic parachite) worked this time and saved him. A broken cam in a Jaguar is seldom as serious!

 

@jagscott

A possible contributing factor is the cam orientation.

You did the first cam with the cam oriented so that the base circle was facing the cam buckets. Less spring pressure.

Then you attempted the second one without moving the cam to a similar relaxed position. There is more pressure involved.

For anyone else following along, the missing step is to finish the first side by undoing the zip tie and releasing the retaining pin. Then, bump the starter to get the next cam into working position. WITH THE FUEL PUMP DISABLED.

The cam bearing looks fine. You could smooth it out a little bit with emery cloth wrapped around a cylindrical object.

Most overhead cam repair procedures note that the lifter buckets wear to the cam lobe it is matched to. Therefore, if someone does not ship the entire head, get the lifter buckets and shims, and make sure they are labeled at disassembly.

In the meantime, put the bearing caps back into proper position with finger tight bolts so that you do no lose the original positions.

When you are finished, you should have: old head, old valves/springs, replacement cam, buckets.matched to replacement cam.

You will need to check all the valve lashes on the exhaust valves on the replaced cam. A little loose=noise. A little tight=burned valves.

 

VERY TRUE! I have had the good fortune of never having an engine failure while flying. However, I am always prepared for it during all phases of flight. I don't particularly like flying single engines at night, can't see where to land when you've got an issue. Thankfully your friend had the parachute option on the Cirrus. I m surprised the cam broke on such a new airplane though.

 

just replace the cam, buckets dont wear into the lobes. Youre thinking about lifters that do wear into the lobes and swapping lifters say on a v8 Ford, and Chevy flat tappet cam can cause isues cause the cam lobes are machined at a angle to rotate the lifters during engine operation. This isnt an issue with buckets., To set clearances all you do is install the cam. measure all the clearances on each base lobe and write each one down. Then remove the buckets(keep them all in the same position, I write to postion down ontop of each clean bucket with a parmanent marker) see or measure what the thickness off each shim is and then do the math to see if you need a thicker or thinner shim to get the clearance in range. If youre good you only have to do it once and not even measure again, but reassemble, But I laways do just to be sure since a mistake can lead to a rough running engine or noisy one. And next time when youre tightening the cam down be sure to go evenly to not bend and break the cam. You just have to slowly tighten each cap and bolt down alittle at a time going back and forth till all the caps are snug then tighten from the center caps out in a circle...

 

A lot of manufacturers do note that matching buckets to lobes on a used assembly is the preferred practice. The way to do this when stealing a used cam is to also steal the buckets. If I had a cam and no matching buckets, it wouldn't stop me from installing it. But, I would prefer to do it with the matching buckets.

AND TO PREVENT A REPEAT PERFORMANCE: ROTATE THE CAM SO THAT THE BUCKETS ARE RESTING ON THE BASE CIRCLE, NOT THE LOBE, BEFORE TIGHTENING.

When doing a full rebuild with the chains off, this is natural because there are no chains in place to prevent rotation. But, as the OP has chains to contend with, it's going to take some fiddling to achieve that. Perhaps going so far as to partially tighten and bumping to get into the right position for final assembly.

@Jayscott

If you do not go through with the full chain set, then you will have to get the new cam onto the sprocket without ever removing that zip tie.