Valve timing fine adjustment

#21
Well, I had a look at the timing today and when the flywheel pin was locked in sure as anything the cam was out by a few degrees. So I set to remedying the situation, I got everything stripped ready for moving the cam round at which point the camchain tensioner unloaded itself and fired all it's internals into the tunnel :evil: :evil:
I then had to remove the sump and fish out the remains of the tensioner, after a fair bit of colourful language and attempting to put the first spanner into space from Hertfordshire I got the tensioner back out and refitted the sump, I rebuilt the tensioner and put it to one side and moved round the cam wheel as described earlier, it was a very easy job to do (as long as you don't drop debris into the engine :evil: ) it turned out to be about 5 vernier teeth out, I buttoned everything back up again and fired up the car and I must say the difference was very noticeable, not only easier starting but much smoother running straight away. I drove the car to the local meet and it's behaving much better and I'm very happy with the results and I think it will improve even more as the accumulated nastiness in the combustion chambers burns away. 4th gear is now my friend again as I can actually gather speed uphill rather than stirring the box to maintain momentum, I will now have to undial all of my previous adjustments I made to get it back to exactly where it needs to be mixture and timing wise.
Making this adjustment has really opened my eyes to how perky the little 2000 engine can be, I barrelled into a few corners driving home earlier a bit too quickly as the car seems so much more spritely and the engine note/feel has altered. I took a few pics along the way too which show the timing being out and the positioning of the camwheel bolts as described in earlier posts.





This is what has to happen if you lose part of the tensioner down the tunnel :evil:
SUMP OUT!
 
#25
Willy Eckerslyke said:
darth sidious said:
Did the pin go in with the EP lining up with the pointer? I recall on the transplanted 2000TC unit we put in our old 2000Auto, the pin wouldn't go in when EP lined up with the pointer, but would when the EP mark was obviously out.

In fact, didn't someone on this forum state some months back they'd heard this "pin won't go in at EP" issue was intentional for some reason?
The manual (official one) says that later engines were set like this to allow for backlash in the chains. It also says you can identify these engines from the shape of part of the cam wheel.
Cheers! :)
 

GrimV8

Active Member
#26
Willy Eckerslyke said:
Hats off to you for getting out of that mess in one day and still having time to drive the car to a meet!
He missed a couple of rounds at the pub but at least it sounded like a Rover when he got there :D
 

colnerov

Well-Known Member
#28
Hi, it doesn't matter how slack the chain is, he shouldn't miss rounds!!

Seriously, I think your'e refering to the implication he didn't refit the tensioner.
I also thought that but I am hoping he just didn't write it down otherwise he will
have to do it again and more!!

Colin
 

GrimV8

Active Member
#29
Even in rage I doubt Jon would remove the sump, fish the bits out to rebuild the tensioner and not refit it :?

Sounded all in one piece to me :)
 

redrover

Active Member
#31
Congrats on getting it sorted, Jon. Looks like it was a beneficial (if challenging!!) exercise for us all.

I must admit, I only made brief reference to the tensioner in my post, because I had already removed it through the little window before starting on the chains, so sorry if I didn't give you enough warning about it's potential to spit half its internal out! As mentioned earlier, I had thought it was worn, but it turned out just to be blocked up :D .

Michael
 

redrover

Active Member
#33
As a final little addendum to this topic from me, I have been doing a bit of light bedtime reading over the last few weeks to try and find out as much as I can about the principles of advancing and retarding cam timing. As this is so easy with the 2000 engine, I thought it might be worth a bit of exploration.

As we all know, the 2000 lump is a SOHC engine, so the inlet and exhaust valve events always happen at the same points relative to each other, but you can move these two events in tandem to an earlier or later point in the cycle. The result is always a compromise of either intake or exhaust efficiency, but the effects can be useful.

In essence:
Advancing the timing causes the inlet valve to close sooner, which causes greater compression to be built up, a bigger (thirstier) bang, and more torque/power etc. The compromise is that the exhaust also closes sooner, causing some degree of strangulation. Furthermore, as the mixture velocity increases at higher rpm, the early-closing inlet valve will compromise the intake. The result of this setup is more torque at the lower end and less at the upper. To some extent, the power curve is simply shifted to the left on the x-axis.

By contrast,
Retarding the timing causes the inlet to close later (up to the beginning of the compression stroke), meaning there is comparatively less vacuum at the ports, compromising usable torque in the lower rev range. However, as rpm increases, the mixture velocity becomes far quicker. Since the exhaust valve also closes later, breathing efficiency is improved. Power in the upper rev range therefore increases. The power curve is shifted to the right on the x-axis.

The latter would explain the lumpy idle and juddery performance below 1000rpm when our timing was retarded due to chain stretch, but I suspect we may pay a teeny-tiny fuel penalty for our now comparatively more advanced timing. As regards loss of upper end grunt, I haven't taken the car fast enough to notice, but I suspect mild changes in weather conditions will have a more dramatic impact on progress than resetting the timing!

Timing changes shouldn't be much more than 4 degrees +/- factory recommendations when using the the stock camshaft. I suspect this translates to 4 teeth of the vernier, which would corroborate a club member's anecdote.

I'm personally not keen to advance my timing any further than standard until after the full engine rebuild, as there are just too many variables otherwise, and experimentation wouldn't necessarily be conclusive or safe. But if anybody has a reasonably tight engine and wants to find out, do let us all know the results!

Michael
 
#34
One thing I would add to your above post is that a later closing exhaust may cause more of a depression in the cylinder after the exhaust stroke is complete and as a result of this the high pressure mixture from the carb rushes to fill the low pressure area, on older engines one way of releasing power is to have a very "standard" inlet cam duration and quite a lairy exhaust duration. This causes the depression I mentioned earlier. This can also cause the charge density to increase and with a flowed head gas speed is increased over a cam with long durations of both inlet and exhaust unless the engine is going to be revved over 8000rpm (thereabouts, stroke dependent).
One way to adjust the timing may be to increase or decrease the valve clearance by a small amount, worth thinking about.
 
#35
Just want to say that the method described here [together with the photos] are worth its weight in gold - works like it says on the box. Many thanks.

A couple of hopefully constructive Barry Cades whilst yesterday's experience is still fresh in the mind:

1. Sometimes the upper tensioner doesn't want to retract [if that is the way you want to go]. If it's refusing to retract, simply put in the allen key, twist and then lock it by pushing into [e.g.] the handle of a small screwdriver into the access port.

2. Plug the chain chest with loose wads of kitchen towel to reduce the risk of dropping or losing bits down into the sump. Kitchen towel expands to fill the space nicely and has more "give" in it than cloth rags when you move the gubbins around.

3. If the tensioner has been slackened, the handle of yet another screwdriver can be pushed into the chain chest on the tensioner side to keep the chain nice and tight as you frig about with the vernier insert - and thus keep a hand free. [Keeping the chain tight is crucial to getting a good result.]

4. After removing the wire circlip and popping out the vernier insert, put the chain wheel up on the camshaft flange [as per instructions] and forget about the "smiley face" bracket [it's nothing but an access blocking pain once the job gets under way]. Move the vernier insert around inside the chain wheel with a mounting bolt in the right hand hole in approx the 4 o'clock position feeling for the threaded hole in the cam with the bolt. You can easily "feel" when the bolt is lined up, then tighten gently to pull the venier insert into the chain wheel. If the teeth aren't meshing, stop, loosen and try again. Once the bolt is home, tighten up and gently rotate the engine to see if the camshaft notch lines up when EP comes around again. If it does, mark the position on the vernier insert and chain wheel with a paint marker [in case of it coming adrift in the minutes ahead], remove the bolt, pop in the wire circlip, and put in both bolts and lock tab, re-check your marks.

5. A head mounted LED torch is brilliant at getting light where its needed - these are cheap-as at any hardware store.

6. Fine control over the EP pointer on the flywheel can be obtained by using a prybar on the starter ring gear teeth during those last critical inches.

7. If you've lost your flywheel locking pin, a 6mm drill bit works just fine.

8. A retractable magnet-on-a-stick is invaluable for hoicking out loose items like wire circlips and chain tensioner plugs etc. Indispensable.

9 A parts and tool tray with powerful magnet base is brilliant at keeping tools, small parts and fasteners from running away - got one recently and now wonder how I coped previously.

8. Don't forget for ignition timing purposes the rear-most cylinder is #1, but for this job #1 is the front cylinder. [Or at least that's the way it seems to work in practice.]
 

Dave3066

Well-Known Member
#36
A quick question...

When I had the head off my 2000SC I took the opportunity to check the valve timing against the markers as described in this thread. As others had found, it was a fraction out and with the flywheel locked at EP the slot in the camshaft sprocket was slightly late (in the normal direction of rotation) getting to the position needed to lock with the key. The EP mark was also slightly out from the pointer with the pin in place but the workshop manual had prepared me for that eventuality so I saw no cause for concern.

So to my question. I removed the spring clip from the camshaft sprocket and disengaged the vernier adjuster, rotated the camshaft in the normal direction of rotation until I could engage the key in the slot, relocated the vernier adjustment to compensate and bolted it back together. What effect has this had on the ignition timing? ie if I've turned the camshaft in the normal direction of rotation independently of everything else have I advanced or retarded ignition timing or has it had no effect at all? If I put a strobe on the flywheel it seems to still be at 4 degrees which is where it was before, but it's not particularly easy to get a nice white line on the right part of the flywheel. I'm thinking that there must have been some effect to the timing as the valves are now operating a fraction sooner than they were before ie the valve timing has been advanced a fraction. If the engine was running well before I did this, which it was, do I now have to advance the ignition timing a fraction to get back to where it was, or will that simply negate any benefits of fine tuning the valve timing.

The reason I ask is because I've not yet managed to get her to run as well as she was before I changed the head gasket. I suspect that is in part due to the carb set up being slightly off when I've reconnected and reset the choke cable but I also wondered if I'd managed to get the engine running as best it could with the old knackered head gasket and now that there is a new one in place it requires further fettling away from that good set-up I had previously achieved.

Other observations that might help are that she used to fire up from warm on the first turn of the starter with no choke or fast idle and tick over fine, now when warm she takes a little longer to start and needs a bit of fast idle to keep her running. Additionally she runs on the hot side. I had noticed this when I bought her and the seller said that she had always run on the hot side but never overheated. She takes about the right length of time to warm up fully and is fine at about 40mph with the needle in the middle of the green section. As the speed increases though the temperature rises to just below the red section and sits there...unless I go down a hill when the temperature falls back again. I've read that retarded ignition timing and obviously too weak a mixture can cause hot running. I believe the mixture is about right so I wondered if it was a timing problem? I shall be getting an exhaust gas analyser to get the difinitive on the mixture but I feel another set of road runs at various degrees of timing will be required this weekend.

As always your thoughts are gratefully received.

Dave
 

Demetris

Well-Known Member
#37
Dave, i think you should put the old gasket back on! :lol:

Seriously now, from what you describe, it seems that the mixture it's on the lean side. Hopefully it is just an adjustment issue, but bear in mind that perhaps you disturbed something and now you have an air leak in the intake.
There's no need to worry about the ignition timing, more so when you already certified that it is correct.
 
#38
Mmm. How did you set the ignition timing previously, Dave? It may be you have a pointer error which now needs dialling out - so check the pointers against a true TDC (ie stick down a plug hole to find TDC from the piston). Then do a colour tune mixture set. If there's still a problem, remember we are running at the top end of ambient possibilities at the moment - probably well ahead even of Greece - it's **** HOT!

Next stage on is to set the ignition timing to what the car wants. ie do an initial set and then do minor tweaks followed by a test run to see if the car is faster or slower. Leave the mixture on the rich side of correct through this process.

Chris
 

Dave3066

Well-Known Member
#39
chrisyork said:
Mmm. How did you set the ignition timing previously, Dave? It may be you have a pointer error which now needs dialling out - so check the pointers against a true TDC (ie stick down a plug hole to find TDC from the piston). Then do a colour tune mixture set. If there's still a problem, remember we are running at the top end of ambient possibilities at the moment - probably well ahead even of Greece - it's **** HOT!

Next stage on is to set the ignition timing to what the car wants. ie do an initial set and then do minor tweaks followed by a test run to see if the car is faster or slower. Leave the mixture on the rich side of correct through this process.

Chris
I'd previously set the ignition timing using the pointer and a strobe on No4 HT lead. Then fine tuned with road runs, adjusting the knurled wheel on the dissy in between. The mixture had been set with a colourtune and I think I've got the hang of using the carb lift pin too :D.

I'll check true TDC against the pointer and flywheel markings before proceeding further. Yes it's been v hot here too but she's definitely running slightly off, not by much, but when you get to know a car you can tell when it's slightly off.

Dave
 

herts2000

Active Member
#40
GrimV8 said:
I think everyone does that with the tensioner once, it's like the apprentice initiation of Rovers :mrgreen:
I haven't :lol:
If you have the head off you can fit the tensioner to the head before re-fitting the head. :D
 
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