After a lot of bad luck (more in the near future) I had to remove the cylinder head (and put it back on again).
Apparently during the process, the serrate adjuster plates in the cam sprockets moved a bit and I now have to align the holes in the adjuster plate with the ones in the camshafts. No problem aligning them at the inlet side but (so far) impossible at the exhaust side.
Looking closer. I see that there is no space left to move the serrated section of the adjuster plates fully out of the cam sprockets: the stepped section (with the two flats) of the “guide pin” through the adjuster plate, is stopped by the aluminium Front Mounting Bracket, before the serrated section is fully out of the cam sprocket.
At the inlet side, the “slotted ear” of the Front Mounting Bracket is slighted bend to the front, giving about 1/8" (3 mm) more space to move the serrated section fully out of the cam sprocket. See pictures below; picture 2 shows the bend section of the aluminium mounting bracket.
Should I also try bending this section at the exhaust side of the engine? I’ve seen quite some Front Mounting Brackets with (at least) one “broken ear” so I’m hesitating to do this.
If I had known this before starting assembly, I would have put the guide pin in a lathe and remove the 1/8" to get more space.
Is there another solution to get the adjusting plate out of the sprocket?
Unless you removed the large circlip in the cam sprocket then the alignment of the cam should not have moved during the head removal and reinstall. However if you need to realign the sprockets then there should be enough room to pull the serrated plate forward, it can be a bit fiddly but you should be able to get it where it’s possible to rotate it. You need to have the sprocket fully on the cam shaft flange and that might need the timing chain to be relaxed a little.
so this view is from the rear–you are saying that with circlip removed, then you can not get the serrated plate out toward the front-its serrations clear enough-so as to rotate it? it is contacting the “storing” mounting bracket for the chain gear? It is hard to tell–in photo of the inward angle of the holding bracket…lines converge from both sides…but if it does lean inward–WHY? can you protect the abysss and surround with saran wrap and file off enough to clear?
Nick
Yelp, you managed to get the plate installed in the first place so it is curious there is not sufficient room now. Anyhoo, I would try looping a strong zip-tie thru the slot and then around the stud, then cinch it down until you have enough room. IF it breaks off, at least you have a tether on it.
Judging by the number of threads showing, I’d say the space difference is about .167"…quite a bit so something is probably bent already.
Hi Bob…as above…if it went on it must come off…they can be very fiddly…just keep at it…i assume your cam is at tdc position where it would have been when the serated adjuster was fitted
Thanks everybody for your advise, although none really solves my problem immediately…
Phil: I had to clean/check everything so I removed the adjusting plates from the sprocket as well. I know it’s fiddly (as I’ve done this several times before on my XK 140). But in this case there’s really very little (or even insufficient?) space to get the adjuster plate out of the sprocket.
Nick: there is a clear difference (for whatever reason) in the amount of space between the inlet and the exhaust side. The picture may be unclear in that respect. Filing a few millimeter off the bracket would be a solution in providing more space.
Dave: I had to slacken the eccentric chain tensioner already. Because both head and block had been skimmed in the past, I had to use a composite head gasket (the new Payen version of 1.6 mm thick). My pistons are about 1.3 mm above the top of the block, meaning the camshaft sprockets are about 0.3 mm higher than normal. There still is enough slack in the chains, but I couldn’t tension the chain first (as per Workshop Manual).and will have to do that after both cam sprockets are in place and the head has been fully torqued down.
Lee, the tie wrap might help as I could generate more force in getting the serrated section out, but it will be tight. It’s difficult to measure the exact difference between the inlet and exhaust side so it might well be 0.167" (or 4 mm against my indicative 3 mm). Good idea to count the number of threads!
Steve: both cams are in the correct position, aligned with the TDC of cylinder 6 and the marking on the flywheel. The distributor arm points to the cylinder 6 spark-plug cable. The engine did run well up to 2 months ago.
I will try it once (or twice…) more, this time clamping the cam sprocket firmly on the camshaft and then try to pull the adjuster plate out of the sprocket. See whether the clamping creates enough space to get the serrated section fully out of the sprocket (so I can turn the serration one or two teeth as that’s all that is required).
If that’s still not feasible I might be temped to push the upper chain sprocket away to the centre and take a file and a vacuum cleaner/hoover, plus putting a piece of cloth in the hole beneath these sprockets. (just to be sure that no aluminium dust gets in the engine).
They need to be absolutely clean to mesh. Just grabbing a handful at hand I can tell you none of these are clean enough to mate without issue. It’s really easy to get them in a bind. There’s no reason you should start grinding on something that didn’t need it before. Two wrongs won’t make a right.
I’m not sure how you could clamp it. Certainly not by using the bolts because the holes don’t line up, which is why you need to rotate the adjuster in the first place. When I do mine I keep a dead blow hammer and a brass drift handy. It’s a highly iterative process where you have to repeatedly tap the gear on and off so it can be rotated one tooth. It needs to be fully on, in order to then extract the adjuster to rotate it. I’d guess that the difference between the easy and hard sides is that on the easy side the gear is a slip fit on the cam, and on the hard one, it’s more of an interference fit. It might be due to gunk, or might just be due to manufacturing tolerances.
Resist the temptation to file on, or pry against the aluminum carrier ears. You see tons of broken ones from this sort of rough work.
Understand your advise and warning. When I remove the camshaft, I can simply push the adjuster plate out of the sprocket using only two fingers. This is still the original matching pair.
In the same way I could probably solve the issue by removing the camshaft and every time move the adjuster plate 1 teeth and assemble the lot again, until the holes match perfectly. But that’s not the way it should be done.
Until now, there’s simply not enough space to get the adjuster plate fully out of the sprocket (with the camshaft in place).
Erica,
I noticed that I had to firmly push the sprocket over the round “end plate” of the camshaft: it tends to move back a little and every fraction of an inch counts in my case. I was thinking using two smaller screw clamps (as used for gluing) to keep the chain (and thus the sprocket) on the camshaft.
Looking at the Main Bracket, the “ear” at the “inlet” side is bent forward which gives me more space to take the adjuster plate out and turn it in the right position.
But I will give it another try tomorrow morning and see whether there’s enough space to get the adjuster plate out and turn it to align the holes. Fingers crossed…
Did you try to remove the bearing cap, the one at Cyl nr 6. Then you can push the cam a little back backwards, as this bearing is centralizing the cam position.
Something is cocked in this. There should be at least 5mm (7/32") between the chain and the batwing. It doesn’t take more than 2mm to disengage the serrated plate. There is plenty of space there without grinding on anything
And that 5mm clearance mentioned above is between the chain sprocket and the batwing. The sprocket doesn’t have to move at all. You should be able to pull the serrated plate back an inch, 25mm, before it hits the batwing. That’s 10 times more space than you need to reposition the plate.
In my case there’s a shouldered shaft (Guide Pin C.2178) that doesn’t allow the serrated plate to move an inch. See picture below. The diameter/width of the slot in the “batwing” of the Main Bracket is not large enough for the shouldered section to pass through this opening.
I used that method as well but then I have to loosen all the other bearing caps (a bit) as well and the camshaft is moving upward, putting more tension on the chain. It’s not the best way to get everything positioned.
Couldn’t work on the car today but hopefully tomorrow.
Hi Bob…just for info…have you worked on this engine before…have you had the sprockets off and set the came timming yourself…im curious becaus it its been assembled before there is no reason why it cant come apart…Steve
That shoulder on the pin has 2 flats. Can you rotate the flats so that they fit through the slots in the batwing? The pin is secured to the plate with a circlp and a star washer, so it is free to rotate.
Yes Steve, I did the complete assembly of the engine about a year ago. The only difference being that the engine was still out of the car with far better access to all parts. See picture.
The engine was running perfectly for a while, until a problem developed caused by “polluted” fuel from a newly coated tank. This caused the inlet valves to get stuck in their guides: three bent inlet valves were the result but fortunately no other damage and it all could be repaired.
I thus had to take the complete head from the block and to prevent any future problems I had all components cleaned in an industrial ultra-sonic cleaner. The 3 valves and all 6 guides have meanwhile been replaced by my engine shop and now it’s assembly time again.
I also don’t understand why I can’t get it done this time. I’m beginning to suspect that there might be some “dirt” between the cam sprocket and the camshaft itself, which would limit the amount of space available to move the adjuster plate out of the sprocket. I also noticed that at the other side the sprocket sits “better” (or deeper) on the camshaft. But that side also has the bent “batwing” creating at least 1/8 to 3/16" more space.
Solved it!
First removed the camshaft to see whether there was something between sprocket and camshaft that would limit the sprocket moving fully on the camshaft, but everything was clean. Also the serrated plate could be removed with just two fingers.
This stubborn old Dutchman (if that is still the correct order) then went back to his idea to create just a bit more space. I used an old chisel and positioned that between the Main Bracket and the chain sprocket (see pic).
The chisel is about 5 mm (3/16") thick and this was enough to create sufficient room to pull the serrated plate out of the sprocket and adjust the two holes so the screws would fit.
Both camshafts are now in the correct position with the flywheel mark aligned. Secured the bolts with wire.
Thanks for all your support and ideas…
