Lack of petrol?

Hi Thomas,

What you are seeing or indeed measuring could also be attributable to worn lifters and camshaft. The very reason in having hydraulic lifters is to eliminate the need to manually adjust the valves. When the lifters and camshaft are well past their best, the outcome will be less than satisfactory. If you are going to remove the timing cover again, why not replace the camshaft and lifters while you're in there? I feel otherwise you'll be doing a lot of work for zero benefit.

Ron.
 
You won't have been measuring a true opening position there Thaomas. The Rover V8 has hydraulic lifters replacing the adjustment on the rockers. They need full oil pressure to expand to the correct length, and that usually takes until at least idling revs. When rotated by hand, the lifters will have bled back, so that the pushrods are effectively shorter than when the engine is running. So the opening angle of a valve will be later than its true value and the closing angle earlier. You can probably plot the mid point between opening and closing and judge your timing that way, but it won't be very accurate.

I would be inclined to trust your previous engineering! If you want to progress further, then I suggest removing the inlet manifood and valley gasket to do a physical inspection of the cam. If you decide to replace the cam after seeing it's surface condition, there's no abortive work as you must replace the lifters at the same time as the cam. Plus you will be much better able to judge cam timing with access to the cam itself!

Chris
 
Chris,
I can follow your thought process, but have 2 queries:

1) I measured opening and closing angles on the top of the pushrod. In my view, those angles would be independent of the actual combined length of lifter and pushrod and show true angles. If I'd measured on the valve itself, then you would be right.

2) The measured 15° difference between target and actual values was fairly uniform across all positions (too early on InOp, InCl, ExOp and ExCl). So I suspect that cam timing is off.

Before changing the timing gear set, the engine was running very smoothly with no suspicion towards worn cam or worn lifters. Mind you, the engine has just covered 105.000 km/65.000 mi.

Thomas
 
15 degrees is a lot to be out. That's multiple timing gear teeth not just one or two. People will sell you vernier chain sets in order to get the last minute of accuracy, never mind degree!

Still, I see what you're saying, and if the engine sems to be supporting your thesis with rough running, you're really not going to be happy until you've had another look!

Seems to me that the $64k question is going to be how do you judge TDC with the front cover off if you don't trust the timing marks? Sounds like a dial gauge down a sprkplug hole?

Chris
 
Interesting, I've done just that on another car yesterday!
So I have the prepared spark plug around and will double check the timing marks and the true TDC.
Will keep you updated.

Thomas
 
That's a relief!

Now to find what' causing the rough running! If you have fitted the electronic ignition we can discount duff points/capacitor issues. Was it running like this before the attention to the cam drive /electronic ignition?

Unless there's something really obvious awry in the carb /fuel department I always start with the igniotion system and work through that before touching the fuel side of the equation. The V8 is extremely prone to cross firing so ignition leads, cap etc don't just have to look OK they need to be top quality items.

I'd be inclined to start by throwing a set of leads, cap and rotor arm on from SimonBBC. His stuff seems to pass the made in China test and his leads are second only to Magnecor (the best if you have deep pockets). Also, how old are your plugs?...

Whilst in the vicinity check you have vacuum advance with a suck on the vacuum pipe to the distributor and also check the rotor arm springs back freely when twisted to verify centrifugal advance.

If you're not confident in the spark delivery a really neat little accessory is neon plug indicators, which you fit between the cap and the plug so that you can see which cylinders are firing and whether any are missing the odd beat:

http://www.ebay.co.uk/itm/4-PC-Heav...iagnostic_Tools_Equipment&hash=item1c284d4f20

and similar.

Chris
 
When you fitted the electronic ignition, did you reset the ignition timing or you left it alone?
Since it is the only other thing that you played with, then perhaps it is just the ignition timing that it is out.
 
Hi,
I couldn't put my mind to rest without taking the timing cover off again and doublecheck the positions of the timing marks on the chain assembly.
The pictures below show on the left side the new chain as installed, and on the right the old assembly prior to removal. In my view, both are as they should. The timing marks are circled in red.



Used the feeler gauge again and measured the valve timing. Reviewing the readings more carefully now highlighted my problem: it' a worn camshaft!
Inlet and exhaust both open 15° too late and close 15° too early (leaving a total opening of only 255° rather than the 285° as specified. So the cam lobes are obvioulsy ground down and a new camshaft and lifters are the thing to do. And off course look again into the ignition as suggested earlier by you guys because that's likely the source of the rough running.

Anybody got a recommendation for good quality replacement cam shaft and lifters?

Thomas
 

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Re:

Thomas-P6 said:
Hi,
Inlet and exhaust both open 15° too late and close 15° too early
Click to expand...
Thomas,
Is that for ALL the valves or just some of them?
If it's all of them, I would guess at your chain being a tooth out, regardless of the marks. Depending
on your chain's pitch, 15 degrees is about 1 link.
If you set the engine up with number 1 at TDC on the firing stroke, where do the marks end up?
I'm not saying your cam isn't worn, but that sounds a lot like you may have 2 problems.
 
John,
that was my first guess: timing is out 15° on all valves, and in the same direction, meaning the chain would be a tooth out! That's why I double checked the timing marks on the chain set up.

But apparently I had an error in my thought process. Timing is out 15° on both, inlet and exhaust valves, but not in the same direction! The graph below shows what I have:


Blue marks:
Inlet should open at 30° BTDC
Inlet should close at 75° ABDC
Duration should be 285 °

Green marks:
Inlet does open at 15° BTDC
Inlet does close at 60° ABDC
Duration is 255 °

Blue marks:
Exhaust should open at 68° BBDC
Exhaust should close at 37° ATDC
Duration should be 285°

Green marks:
Exhaust does open at 73° BBDC
Exhaust does close at 22° ATDC
Duration is 255 °

So my guess now is worn cam shaft lobes. Haven' yet checked valve lift but will do so and let you know.

Thomas
 

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I think we can take bets on it being less than 10mm!

I must say I would now buy cams and engine parts from http://www.v8tuner.co.uk/index.php on the grounds that I think you would get very good advice from them. If your spoken English is as good as your written, then just ring them up and talk through what sort of cam etc you want. They may share my view that the 3.9 cam runs out of power too early for a saloon, especially with Autobahns etc to play on! It could severely dent top end high speed cruising?

Chris
 
Have now taken lift readings directly off the pushrods: both inlet and exhaust have about 0.250" (6.35 mm).
I have been reading that the standard cam lift is 0.390" (9.9 mm) but I 'm not sure if this means the lift of the cam lobe, or the true lift of the valve which would be bigger due to the rocker arm geometry. Couldn't find any true specs in the workshop manual.

Thomas
 
Just found the information that the standard rocker ratio is 1 : 1,6.
This would give my valves a lift of almost exactly 10,0 mm which is to spec!
Why then should I change the camshaft at all?

Thomas
 
Hello,

I dug myself a little deeper into this. Removed the inlet manifold and checked the condition of the camshaft lobes and the surface of the lifters.
To me, they all look alright. Measured the cam lift directly of the lobes on serveral cams, and all read about 6.25 mm.

Here is what the lobes look like (same lobe, taken from 2 angles)...


... and here are a couple of the lifters:



Does this look suspicious to anyone out there?

Thomas
 

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Hi Thomas,

When new, the base of each lifter is ground with a spherical radius so that the centre sits approximately 0.003" high when compared to the perimeter. You could check for this convex nature by measuring your lifters.

As they wear the base of each eventually becomes flat and then concave. From your photo they certainly look fine as do the lobes with no indication of broken edges.

Just remind me Thomas, how many miles are on your camshaft and lifters?

Ron.
 
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