Top Timing chain just sits there?

(george leicht) #1

The enemy of good is better

Finished fitting the head to the XK engine, a lot of fiddling with the timing chains, everything was turning correctly including both cams, but intake cam was just a few degrees off, reset the cams, tightened everything up.
And now the top chain does not turn, I can turn the crank and the bottom chain moves, but no movement transferred to the top chain.

I assume I sheared something on the intermediate timing gear. Any suggestions on what I screwed up?


1965 Mk2
Cincinnati OH

(Nick Saltarelli) #2

Careful turning the crank lest you foul the valves with the pistons and bend their stems.

The intermediate sprocket is not keyed. It is one piece so when the bottom chain turns it must also move the top chain. The only way the top chain will not move when the bottom chain moves is if a) the chain is broken or b) the chain is not engaged in the teeth of the smaller gear of the intermediate sprocket.

(Nigelplug) #3

Stupid question but you did put at least one bolt into each camshaft flange through the vernier adjusting plate? If you have ,I’m a bit baffled! Only logical explanation is that the top chain broken! Not that you should, but how by many degrees have you turned the crankshaft through?

(Ian) #4

I take it when you say you can turn the crank , that you mean just enough to take up the slack in the bottom chain ?

I would take the cams out , then turn the crank , see if the top chain moves free , if its ok , re-time it all up again .

How did you adjust one cam by a few degrees ?

The timing gauge sits on the head and in a slot in the cam , once that is done , you can’t really just adjust one cam , maybe you got the intake cam 1 tooth out , and a valve is hitting a piston , that would jam the top !!

(Lee140FHC) #5

You can adjust each cam by as little as 1.375 degrees…131 serrations = 2.75 degrees/serration. But because there are an odd number of serrations, you can adjust the relative cam setting/timing by half a serration…1.375 degrees. The Manual touches on this, though quite tersely and I suppose some miss this info.

A broken chain would have a tremendous amount of slack below each cam sprocket and should just pull out of the timing chest.

(george leicht) #6

I want to thank everyone for their input. We had to leave for the Stratford Festival this past week, but before we left I gave the engine a turn or two (nut on the crank) and the top chains were turning. So I don’t know if I am just going mad., or had just inhaled too much lacquer thinner cleaning parts.

The engine sits on a test stand so I have full access to the front. I plan to first remove the timing chain housing and see what is going on. Then, if I have to, pull the head. I’m using a cometic head gasket and Cometic says I can reuse the gasket as long as the engine was not started (i.e. heated)

Will report back. And thanks again.

Puzzled in Cincinnati

(Pat Harmon) #7

You should not have to pull the head unless you suspect valve damage. I would try turning the engine with a wrench through two revolutions to see if you have any valve/piston interference. Follow the valve/cam setting procedure outlined in the shop manual. Plan on taking two days to set the cams and valve clearances.
Pat H

(tony) #8

snake cams that fit a phone or laptop are extremely inexpensive, and can be used to look down the timing chest, another poster did this recently, they can also inspect bores, piston tops etc etc

(Nigelplug) #9

Another daft idea maybe. Had you removed the front damper bolt, and not tightened it up?
If so,you may have thought the engine was turning, when in fact,all you were doing was tightening the nut onto the damper face?

(george leicht) #10

OK, after a week off, I went back to the engine. Either I’m crazy, or it’s magic, but tried one last time to set the valve timing before removing the timing chain cover and possibly the head. Surprisingly it all seemed to come together. I am about a quarter tooth off on the intake side of the engine. i.e., if the exhaust cam is set correctly with the cam template at Top Dead Center, the crank would have to advance about 4 degrees (after TDC) to be dead on the with the cam template.

I think that is where I was two weeks ago. So absent anyone posting OMG!,. I’m going to leave it that way.

Again, I want to thank all of you witnessing my decent into madness. .

cincinnati OH
1965 Mk2 .

(tony) #11

I had some trouble years back on a 3.4 after dismantling the inner splined cam gear from the outer,
and then had trouble getting the cam bolts back in.

The chain gave me an issue as well…iirc, its much better to do the exhaust cam first, otherwise the chain can “bunch” with too much slack, and it wont go back together right

in the archives Terry Handley details that certain slight variation from factory cam timing can be useful

(Steve Tennison) #12

I’ve just been checking and the upper chain simply rotates, its not broken, but just not attached to the lower timing chain. Hopefully i have not bent any valves as I was just starting to rotate the crank to re-check the valve gaps when I noticed the cams were not rotating. The only thing I can see in the manual is that there is a key that locks the upper chain sprocket to the upper shaft but I cant see how that could break.

(Steve Tennison) #13

Hi - I have just posted a message in the e-type section but I have exactly the same problem as George except my problem is still there ! Looking at the picture below and the series 1 work shop manual it shows that the intermediate sprocket of the upper timing chain is attached to the intermediate sprocket of the lower timing chain by a key - its not a one piece assembly. I wonder whether somehow this key could shear


(Nigelplug) #14

The only thing that connects the upper and lower sprockets is the chains. The only key in the whole issue is the one locating the lower sprocket to the crankshaft.