Talk Morgan Forums Community Vehicle Talk (non-Morgan) TDC and tappets

Greetings all

I'm working through my recently purchased digger as I go along (new engine oil and filters done already) .... I want to check/adjust the tappets as I guess they haven't been bothered in a while.

The manual says to turn the crank using the pulley centre nut and use associated pulley marks to determine TDC on compression stroke for each piston in turn .... both exh and inlet can be set to 25 thou then.

Due to the installation when fitted to a digger it would be an engine out job to see the marks (accessing the nut to turn over the engine in the first place will mean me bodging up a cranked spanner to get on it and still be able to turn the thing over!).

My intention is to turn the motor until both valves on the target cylinder are closed, then inch it round until there's max slack in the tappets and reset it there. Then move on to the next cylinder.

Does anyone have a major misgiving about doing it that way or can suggest a better method? (I did also consider removing the glowplugs and using a slim metal rod to find TDC but want to keep messing with the engine to a minimum as it's running fine)

Many Thanks

K

Can't you get a top dead centre tool? It is a rod that has graduations markings so you can see tdc therefore degrees before and after.
Mind you if it runs it might be better to stay way

Cheers John ..... Don't they fit down a plug hole? .... it's a diesel and although I agree that leaving well enough alone is the best policy I'd rather pull a glowplug than an injector. The 'bit of rod' idea is really only a cheapskates version of a TDC tool. 🙂

It may not need adjusting but not knowing what it should sound like (and listening to a diesel under a lifted cowl in a steel shed) it sounds like it needs snugging up a bit (but nothing worryingly so)

K

On a 4 cylinder engine, simply use the “rule of 9”
You don't need to find T.D.C. but, just view the valves when fully opened as you rotate the crankshaft.
Numbering the valves from the front of the engine from 1 to 8:
With number 8 fully open, adjust the gap on number 1
7 open, adjust 2
6 open adjust 3…etc
. i.e. always add up to 9
Of course, to save lots of engine turning, you don't need to do them in strict numerical order…as you rotate, simply spot the valve that is fully open and then adjust the one in a position that adds up to 9.

Cheers Dejay .... sadly this is a 3 cylinder diesel ..... according to the manual you get the cylinder to TDC on the compression stroke (both valves closed) and then set both exhaust and inlet to 25 thou .... my only niggling concern is that maybe there's some coincidence of the cam at TDC that allows the same gap for both inlet and exhaust (often there's a difference) and setting them when there's maximum slack rather than accurate TDC might mean one ends up maladjusted (and there's only one maladjusted thing allowed on the car and that's me!🙂)

K

I missed the diesel bit. Sorry

As it’s a triple, then it will most likely have a 120 degree crank, so think it best to follow the manual. If you cannot get to see timing marks, then the only sure way is to use a rod inserted to rest on the piston top as discussed earlier.
However, my other concern is how you intend to “inch” the engine. My experience of long ago in attempting to do that using the starter is extremely hit and miss…more often than not: miss! A spanner on the crank is best or alternatively rocking it in gear, but that may not be practicable with the weight of the digger.
So failing all that, my thoughts return to your original thoughts. If you set them when they show maximum slack then it should be fine, but as said, the big issue is being able to inch it gradually. If you cant get to the crank, might it be possible to get a spanner on the alternator or fan pulley, as long as glow plugs are removed to release compression of course.
Alternatively, there’s the old adage: if it ain’t broke, don’t fix it!
Good luck.

I'm hoping to bodge up a custom spanner to reach in to the nut on the crank pulley .... starter is a non-starter (so to speak) for fine work and it's tracked so no bumping.

Will see how it pans out but I'm leaning towards a thin rod down the glowplug holes to find TDC in order to be sure ... but if that proves impractical I'll fall back on finding the slackest point.

K

Good luck with removing heater plugs - if they haven't been moved in a long time...

I would just find valve fully open position visually then turn crank 360° (assuming you can) and adjust. This works for any four stroke engine and you can be assured you are adjusting on base circle of cam.