Series 2 3 MB diesel engine camshaft timing cheat?

G'day Folks,

I can probably work this out myself (and will do so if necessary) but was wondering if others have done this before.

I have my engine on a stand - no flywheel adapter / housing fitted - no flywheel fitted. I don't really want to lift the <BLEEP>ing engine of the stand yet again to fit the flywheel at this stage just to set up the camshaft timing. No head is fitted (and of course this means no valves or tappets or the rest of the malarkey).

Whilst I expect I'll get swamped by "why not wait until later when everything is all fitted" comments I'd like to time the camshaft in this "lower block" state.


It seems to me to be the logical thing to do at this time with a push rod engine like this old beast.


So camshaft is fitted and the cam followers are in place: It is possible to measure with a DTI the rise and fall of the exhaust camshaft lobe on #1 cylinder.

Pistons are fitted: It is possible to measure TDC

Flywheel is off: But you can measure (by counting teeth) on the ring gear the position of the "EP" - exhaust peak position with respect to TDC and convert this to degrees

So it should be easy enough to work out where the camshaft position should be set in relation to the crankshaft position - right?


Clear as mud?

If it is not as clear as mud and you understand what I mean and you've done this before I'd like to know the values you calculated so I can check the ones I'm probably going to have to calculate myself.


(If there's actually a Land Rover routine for doing it this way I'd like to know about it as it isn't covered in the Green Book. It wouldn't surprise me if they were set up at the factory in the way I'm suggesting as waiting for the head and the rest of the valve gear and then setting up the timing is potentially asking the valves to meet the pistons!)

Definitely doable, but have you got the info relating tdc piston to valve opening/peak/closing? Graphs of this are used in engine design, but I've not seen it released to the wider public. In the old days that would be like giving your ecu mapping away to the competition...

I'd hazard a guess that you'd get it accurate to one tooth by working from any keyway that you've got.

boguing said:

Definitely doable, but have you got the info relating tdc piston to valve opening/peak/closing? Graphs of this are used in engine design, but I've not seen it released to the wider public. In the old days that would be like giving your ecu mapping away to the competition...

I'd hazard a guess that you'd get it accurate to one tooth by working from any keyway that you've got.

Click to expand...

There's the "EP" mark on the flywheel - you just have to count the teeth from TDC

I'll do it tomorrow

Yes, you can do it. But don't count teeth. (From memory) ep is 109deg, the teeth are 7.5deg so you won't get a whole teeth count.
Use a timing disc.

For the avoidance of doubt, as they say, I meant that by accurate measuring you'd get the cam relationship close enough that it would be obvious which tooth of the cam drive to engage. Pretty sure @Stretch got that..

SpringDon said:

Yes, you can do it. But don't count teeth. (From memory) ep is 109deg, the teeth are 7.5deg so you won't get a whole teeth count.
Use a timing disc.

Click to expand...

109 degrees after TDC sounds a bit early to me for a fully open exhaust valve. Most engines don't start to open their exhaust valves until very close to BDC (bottom dead centre) - say about 20 degrees or so before BDC...

...may be 109 degrees before TDC - that might work assuming the valve starts to open at about 20 degrees before BDC then it rotates another 70ish degrees until fully open and then there's another 70ish degrees for it to close - at about 40ish degrees before TDC (and the piston gets too close to the valve)

Does that sound about right?

Obviously I'm gonna have to check this really carefully! (As you can see above there are too many "ishes")

boguing said:

For the avoidance of doubt, as they say, I meant that by accurate measuring you'd get the cam relationship close enough that it would be obvious which tooth of the cam drive to engage. Pretty sure @Stretch got that..

Click to expand...

Oh yes - I hope so - it should be possible.

Like I said I can't imagine Land Rover wouldn't have done it this way when building the engines. You could in principle make a go-no-go gauge that drops on top of the cam follower on the exhaust valve to get the camshaft in the correct position and then just align the marks - I can't see them messing about with clock gauges and the like in a manufacturing assembly line.

It's going to be before TDC. It's not that far off the ones I remember - you sure you're not recalling opening angles?

I didn't say after or before. It is as you say before as it wouldn't make much sense to be after.

In open 16btdc
In close 42abdc
In peak 103atdc
Ex open 51bbdc
Ex close 13atdc
Ex peak 109btdc

From the workshop manual engine tuning data section (it is a diesel isn't it)

Doable with the DTI on Number one ex cam follower, just be sure you are not 180 degrees out.

SpringDon said:

I didn't say after or before. It is as you say before as it wouldn't make much sense to be after.

In open 16btdc
In close 42abdc
In peak 103atdc
Ex open 51bbdc
Ex close 13atdc
Ex peak 109btdc

From the workshop manual engine tuning data section (it is a diesel isn't it)

Click to expand...

Perfect!

Thank you very much.

As a matter of interest my measurements and calculations confirm the 109 degrees before TDC (as you said and as you remembered)

Here goes!

Marks on the old flywheel



There are some convenient markings close to TDC that have helped with my calculations - note 14 degrees and 16 degrees marks



The point on the flywheel I'm interested in at the moment is the "EP" - exhaust peak - mark

Measuring the distance along the circumference of the flywheel between TDC and EP with a handy bit of paper =>



Then I went into open office (yeah f you Microsoft I use alternatives!) and did some calculations from the measurement of the flywheel diameter...




...the measured diameter gave the calculated circumference. The measurements of the distances between the TDC mark and the 14 degree and the 16 degree mark are compared with the expected distances made from the circumference calculation. (Quite close considering they are small measurements made with paper and a ruler)

The measurement of the distance between TDC and EP has been converted to an angle - which has been quoted as 109 degrees before TDC - so my measurements are in agreement with the data!

divie said:

Doable with the DTI on Number one ex cam follower, just be sure you are not 180 degrees out.

Click to expand...

Thanks chap - with the head off the engine even I couldn't cock that up!

Well done on matching the engine data with your measurements. But I'd still say use a timing disc, they're so cheap and (I would normally say) more accurate.

SpringDon said:

Well done on matching the engine data with your measurements. But I'd still say use a timing disc, they're so cheap and (I would normally say) more accurate.

Click to expand...

I don't have a timing wheel but I could make one as they don't strike me as being particularly cheap (unless of course you're talking about the angle measuring attachments that people sometimes use with torque wrenches).
I think I'm probably going to invest in a digital spirit level that will also be useful for the chassis work I'm about to start - I can then just rig something up on the front of the engine.

Depends what you call expensive, I suppose but....
http://www.ebay.co.uk/itm/005098-MO...hash=item360e4faed3:m:mVlJwGgZvykrKC3q2OEs7dw

For example

divie said:

Doable with the DTI on Number one ex cam follower, just be sure you are not 180 degrees out.

Click to expand...

you cant be 180 degrees out until you time injection pump

SpringDon said:

Depends what you call expensive, I suppose but....
http://www.ebay.co.uk/itm/005098-MO...hash=item360e4faed3:m:mVlJwGgZvykrKC3q2OEs7dw

For example

Click to expand...

thats what i use and what you need

Stretch said:

Perfect!

Thank you very much.

As a matter of interest my measurements and calculations confirm the 109 degrees before TDC (as you said and as you remembered)

Here goes!

Marks on the old flywheel

There are some convenient markings close to TDC that have helped with my calculations - note 14 degrees and 16 degrees marks

The point on the flywheel I'm interested in at the moment is the "EP" - exhaust peak - mark

Measuring the distance along the circumference of the flywheel between TDC and EP with a handy bit of paper =>

Then I went into open office (yeah f you Microsoft I use alternatives!) and did some calculations from the measurement of the flywheel diameter...

...the measured diameter gave the calculated circumference. The measurements of the distances between the TDC mark and the 14 degree and the 16 degree mark are compared with the expected distances made from the circumference calculation. (Quite close considering they are small measurements made with paper and a ruler)

The measurement of the distance between TDC and EP has been converted to an angle - which has been quoted as 109 degrees before TDC - so my measurements are in agreement with the data!

Click to expand...

presumably your going to find true peak by marking the same height pre and after peak on cam sprocket and finding the center between the marks

SpringDon said:

Depends what you call expensive, I suppose but....
http://www.ebay.co.uk/itm/005098-MO...hash=item360e4faed3:m:mVlJwGgZvykrKC3q2OEs7dw

For example

Click to expand...

Oh well done. Everything over here seems to cost 40 euros a piece. Whilst it is only a small one I reckon it'll do - as @boguing says you only need to go one tooth one way or the other.

SpringDon said:

...
In open 16btdc
In close 42abdc
In peak 103atdc
Ex open 51bbdc
Ex close 13atdc
Ex peak 109btdc
...

Click to expand...

I forgot to ask but could you check those valve opening and closing values? It looks like the inlet valve opens before TDC which can't be right - and the exhaust seems to close after TDC which also will cause trouble. This isn't a safe engine.

(I believe the EP value as I've measured the markings of course!)

jamesmartin said:

presumably your going to find true peak by marking the same height pre and after peak on cam sprocket and finding the center between the marks

Click to expand...

Yep - I also have to go one way and the other to find true TDC as well because I don't have the flywheel fitted. So for both positions I need to make sure I get the right place.

Stretch said:

...

I forgot to ask but could you check those valve opening and closing values? It looks like the inlet valve opens before TDC which can't be right - and the exhaust seems to close after TDC which also will cause trouble. This isn't a safe engine.

Click to expand...

Those are definitely the figures from the manual. And you may have to think about the engine a bit more. Even an low tuned engine will start to open valves before tdc, the plan being that the piston will have gone by the time the valve occupies the same space.
Also bare in mind that the cam rotates at half the speed of the crank.
Also it needs to have valve overlap so that gas is scavenged, ie the inlet opens as the exhaust is closing so that fresh charge helps to push spent gas out. This also help to fill the cylinder more efficiently.
As far as I know, no 4 stroke open valves after tdc.

This is a very safe engine and is reasonably conservative timing. If you want to see hairy timing, look at the figures from a zx10 or panigale.