WOW red letter day today or what - ONE YEAR - yep - ONE YEAR since I started this thread!
Oh how time flies!
Oh what fun I've had!
Oh it is so surprising the Land Rover is STILL in bits!
(Too many exclamation marks I know - makes me sound like one of those retarded Dutch service centre a-holes who reply to with emails with=>
"Thank you for your email!"
"DHL only employs cheap labour who can not read!"
"DHL hopes that you will receive your parcel in the very near future!" )
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Anyway - looking back at the last year I guess progress has suffered at a result of fun.
Fun like my stubborn refusal to remove that effing engine from the engine stand again until it is ready to be fitted to the chassis...
...I'm still messing about with the camshaft timing - I get the impression I'm probably being too precise about it.
See what you think.
Finding TDC has been fun. The "normal" way of doing this (when you haven't got a marked flywheel fitted or any other markings on the front of the engine) is to use a degree wheel and then measure the height of the piston one side of TDC at a known height - note degree wheel position - and then set the piston height on the other side of TDC at the same height and note the degree wheel position.
There's then a fair amount of messing about adjusting the degree wheel so that ZERO on the scale actually is TDC: Tightening and loosening the nut on the end of the crankshaft and resetting the degree wheel...
Once that is sorted out you do a similar thing with the camshaft - rotating it one way and then the other at known heights so you can find the middle point / highest point on the cam lobe.
You can just about see the pencil marks on the camshaft timing cog in this picture =>
Three marks at the top of the cog - one one side - t'other t'other side and the guessed top mark carefully judged with a Mk1 eye ball.
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The plan was then to rotate the crank to 109 degrees before TDC - setting the compression stroke - which is the "EP" exhaust peak position which is where the highest point on the camshaft should be.
Simple - eh?
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Unfortunately in the real world (much like DHL actually performing its primary task - delivering parcels) life isn't that easy or straight forward.
I know this won't be popular but this isn't a Mercedes engine!
Two problems have been noted:
1) "Keeping the chain tight on the driven side" as per the instructions in the Green Book probably isn't sufficient - I think it is best to fit the timing chain tensioner and spin the crank a few times to make sure the marks on the timing chain wheel and the flywheel / degree wheel match
2) This is an old Land Rover and we have to deal with "bigger clearance" than I would normally have to consider.
Here's an explanation of how even with a degree wheel and a DTI things can go a bit wrong - if you are not careful your carefully made marks will wander (!)
Clearance is needed in all moving parts - too little clearance and things won't turn - they just stick and perhaps friction weld themselves together - so clearance is necessary but you do have to keep an eye on its effects.
(I hope the next pictures show things clearly - I gave up trying to get the trim function in LibreCAD to work properly and I'm not firing up Windows to try and use my 1996 version of Autosketch)
I've gone a bit old school and resorted to photographing cut out bits of paper.
Turning the crank clockwise =>
And you can see the little end and big end journals "roll around" within the clearance
Turning the crank the other way (anti-clockwise) you get the little end and big end journal / wrist pin to "roll around" within the clearance the other way =>
I've shown in red where the (exaggerated) gaps are.
I hope it is clear that you can see that the direction of the crank being turned makes a kind of "sloppiness" in the height of the piston at TDC. You not only get small changes at the end of the piston stroke (the piston has to stop and go back the other way!) but you also get a vague measurement because of the clearance and the rolling about of the wrist pin and the crank journal within the clearance of the little and big bearings.
Note - on this 3MB Land Rover engine with new parts - the clearance is such that I have been able to detect differences in piston height position even when turning the crank in one direction - limiting the rolling around effect of a change in direction.
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I've been busy - doing an 'O' Level physics-like experiment that I never had the chance to do at school!
After setting the camshaft position in accordance with the procedure in the Green Book (well slightly modified as described above) I've then been measuring piston height and cam lobe rise as a function of crank position (degrees)
For the first attempt I came up with this =>
Little bit difficult to see again - sorry - but the big "sine wave" is piston position and the little bump underneath is cam lobe height. Even after messing about with the degree wheel for quite some time rotating the crank one way and then back the other, I found that it was about 3 degrees out. My first attempt at positioning the camshaft was 10 degrees out! Not good.
It isn't like I'm not being careful.
Second attempt at camshaft positioning =>
From the measurements I can see that I'm still 3 degrees out.
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I'm now quite interested to see how this positioning compares with the flywheel markings - so I might be fitting that flywheel after all to see!
