Checking and setting the valve clearances is a job which often gets overlooked. Over time, and with wear in the valve seats, the valve tip clearance becomes reduced. For this reason, it is important to check the valve clearances.
For a full explanation of these procedures, you may find our Perkins A3.152 Engine Rebuild DVD useful.
I am setting the valve clearances for the first time ever on my MF135. Can I just check the process – I presume you use a spanner to secure the tappet rod at the bottom, then loosing the lock nut above that and then adjust the clearance by turning the bolt at the top? Am I correct in thinking that this whole assembly is free to rotate, presumably to even out wear on the head?
The cold clearance should be 0.30mm for both inlet and exhaust – the book says to get the TDC line in centre of flywheel inspection hole and check numbers 1,2,3 & 5 – then rotate the flywheel 360 degrees and check numbers 4 & 6 (I presume all numbering is from front of engine back?). I have been surprised to find on my initial check that No.1 valve was close to 0.30mm but every other valve was more or less completely “tight”. Is that unusual or am I doing something wrong?
The Answer From VTE…
Firstly, yes all numbering is from the front of the engine back.
As for the “tight” valve clearances, this is not unusual to occur as the engine vavles wear against their seats. Everytime the valve clatters against its seat it slowly wears until eventually the vavle starts to receed further into the head which is what narrows the vavle tip clearance. This is commonly known as “valve seat regression”.
This is why the valve clearances should be checked and adjusted at the appropriate service interval. The recommended vavle tip clearance is 0.012 inches (or 0.3048 mm).
You are correct that the cam followers do rotate during operation, this is indeed to prevent them from wearing unevenly.
Another thing to check before you tighten down the rocker shaft is the oil flow setting to the bearings. This will have been calibrated and the punch mark scribed in the factory. The groove in the shaft needs to be lined up with the punch mark. If you look carefully at the photo at the top of the page, you can just see the punch mark that the groove has been lined up with.
This following question has been asked by someone who wishes to replace the timing chain on their Standard 23C engine.
I am trying to read the lines between the Engine Rebuild DVD and the Workshop Manual on the subject of Timing Chain Replacement.
I am pulling off the front of my ’59 MF35 4 Cyl Diesel (to get the radiator recored)….so my thinking is “Why not replace the timing chain and tensioner while I’m there?”
Do all I have to do is turn the engine to TDC, hold it with a pin in the flywheel, remove the chain and tensioner and replace…ensuring that the small bolt hole in the camshaft gear matches up when putting tension on the left side of the chain?
Second question, “Would I then have to retime the fuel injector pump afterwards?” I have no idea if this is going to be more complicated than its worth…..the timing chain and tensioner may be ok…..but why not do it, eh?
The Answer From VTE…
Firstly is the tractor starting and running OK. If it is all OK, then maybe you don’t need to replace the chain and tensioner.
You can remove the cover to inspect the chain without disturbing any of the timing components. Look to see if the chain links fit on the sprocket teeth centrally (as shown in the DVD). You can replace the tensioner without removing the chain (and without disturbing the timing).
The setting of the valve timing (which is controlled by this chain) has to be done with number 1 cylinder on top dead centre on its compression stroke (i.e. both valves closed). The timing hole in the flywheel holds the engine at 16 degrees before TDC which is used for the injection timing – which is timed after the valve timing has been set using the chain.
If you choose to remove and replace the chain then you will need to follow the timing procedure as per the DVD. Once you have set up the timing of the chain you will need to check the timing of the injection pump.
Cheers, you’ve given me the exact info I’m looking for….the tractor is unrestored, but running ok…I get the difference in valve timing vs injection timing now…I hadn’t picked that up before.
So if I replace the timing chain, I’ll need to set up the chain timing and then follow up with the injection timing. Got it.
In my case, I think that I’ll just do an inspection. I just remember rebuilding Standard Engines (Triumph TR3′sand 4′s) back in the day and the timing chain and tensioners were always suspect and had to be done every 30K miles….with this tractor, who knows?….no idea of its maintenance history…but there is no rattle.
Ihave 2 questions about the draft spring nut,
What is behind the grub screw on the side of the housing, I have to drill the screw out as the hex socket is rounded off and the screw is rusted in tight.
Also, is there a tool available to undo the nut or do i have to make something up.
Steve, i have ordered the video, just cant wait for it to turn up,
Dave behind the allen headed screw there is a piece of lead shot which squashes onto the adjusting nut to keep the nut tight. There is a special tool available but you can use a hammer and punch to turn the nut round using the cutouts on the outer rim…..Regards…Geoff
Hi Again, Thanks Fergie Man.
Ok I’ve drilled out the allen headed screw, something very hard is behind the screw, I think its a ball bearing, but i definitely cant drill through it, not even making a dent in it, there is still a ring of the screw holding it in place due to the tapper of the drill bit, going to reshape the drill bit to be concave so i can cut the last thread out of the screw and try and retrieve the ball.
I tried using a punch and hammer on the nut, but I can’t shift it. Possibly still too much pressure from the plug, I’m still open to suggestions.
Ok, with a great deal of exasperation, (big mallet, punch and frustration), I undid the nut and removed the draft control spring assembly, the cylinder was chock full of rust dust, Fergie Man is right, there is a lead pellet sqaushed into the thread area against the nut, but still can’t get it out or drill through it, something like a ball bearing between the pellet and the grub screw, looks like oxy torch time to melt it out.
Removed the pin from the yoke when undoing the plunger but still tore the shaft apart at the end of the thread, rusted solid, lucky sparex and Bareco sell spare parts for all the components so, new shaft, nut and boot ordered, drilled out the yoke and re- tapped it.
Thanks for the help,
The injection pump timing gear must be fitted correctly in order that the injection pump timing is correct for the Standard 23C engine.
The process of how to do this is shown in our MF35 (23C) Engine Rebuild DVD.
One thing to be aware of is that the measurement (45 degrees anti-clockwise from the master spline) is not definitive, but approximate. Another difficulty here is that the gear rotates as it slides in and meshes with the intermediate gear. It is the fully meshed poistion of the gear when the 45 degree line should be close to vertical.
After fitting the injection pump it may be found that the ‘G’ mark will not line up with the circlip as it should. If this is the case it would then be necessary to rotate the injection pump timing gear by one tooth (in either direction) and refit.
It is quite common for rain water to get down a tractor exhaust pipe and into a cylinder. Often people have put a tin can over the exhaust to protect it, but then the wind has blown the can off.
The question is what we need to do to remove the water and make the engine safe to start.
At any one point in an engine’s rotation it is probable that at least one exhaust valve will be open, and therefore some water will have got into at least one of the cylinders. This water must be removed.
The reason the water must be removed is that water is not compressable. So if you were to leave the water in the cylinder then the pressure would put excess pressure on the valves and likely bend a connecting rod, the crank or do worse damage.
You will certainly need to remove the exhaust and exhaust manifold to remove any water that is still in there.
You will also need to change the oil in case water has run down into the sump. You should really change the oil before undertaking the next procedure of turning the engine over.
Remove all the injectors (or spark plugs if a petrol engine) and make sure there is no dirt around the injector ports. Then turn the engine over, first by hand a few times and then by using the starter motor. Hopefully this should squirt the water out of the cylinders. The engine could be seized (rusted) if the water has been there for some considerable time. In that case you would need to follow a procedure for unseizing an engine.
The water may have caused rust on the valves or cylinder liner. You would need to remove the cylinder head to inspect this.
There is a difficulty in knowing if you have got all (or sufficient) of the water out of the cylinder so it does not cause hydraulic lock. Obviously expelling the vast majority of the water will reduce the chances of hydraulic lock occuring.
I would keep checking the condition of the oil once you get the tractor running again. It would be prudent to change the oil again within a few moments of running the engine and then maybe again after running the engine up to temperature (a hot engine will help evaporate and then emulsify any water into the oil). Certainly you should keep an eye on the physical appearance of the oil.
One More Thing.
If ther have been freezing temperatures whilst the water was in the cylinder, this could have cracked the liner or block.