23c engine

[Mydexta]

Update

Head had new valves fitted and seats recut, new stem seals were fitted and it was skimmed. The crack was investigated and it was discovered that it shouldn't be of any bother to the performance of the tractor. It was refitted and starting and running well, although possibly a bit warm, however 2 weeks ago it became increasingly difficult to start and ran warmer than ever. I managed to get a shot of another head and the tractor ran perfectly, not heating and sounding so much better than before. I put the original head back to the workshop who carried out the work to get it pressure tested and they are saying that the crack isn't causing any loss in pressure

Anyone have any other ideas

 

[Ley253]

As you now have the head off, check the liners are square to the block face, frost can distort these these engines without cracking them! Next, make sure you have the correct head gasket, there are many out there which are too big in the bore, and dont seal on the liner top. First symptom is large amounts of crankcase compression, as the inducted charge, when compressed, goes down past the outside of the liners! The engine can also rattle, in bad cases, the liners go up and down with the pistons! To improve the starting, open out the hole in the pre combustion chambers a little, that works wonders!

 

[Ley253]

Didnt see your last post so some of the info wont be of use. But, I would bet that the valve seats have been cut too deep, and thats the starting problem. By lowering the valve into the head, the compression is reduced just enough to cause this. Even the 135 Perkins is prone to this, and thats direct injection, your indirect engine wont stand a chance!

 

[Mydexta]

Tractor was starting fine when head was first refitted in the summer, 30-40scs of heat and away it went, even at -2c

What in thinking is that the crack between the valves is connecting the inlet and exhaust ports, so the cylinder is recycling hot gasses and running hotter. I don't know if the pressure test carried out by the engineers tests the water system only or if it tests the inlet/exhaust system aswell

 

[Ley253]

Only the coolant side.A local 23c in a grey and gold starts with no heat, even in winter. This has new liners and pistons bearings etc and the head has been modified by opening the combustion chamber entrances. I dont see an inter port crack causing much problem, the gasses will take the course of least resistance, and thats up the exhaust not through a crack. Was the engine boiling, or just spitting out coolant?

 

[Mydexta]

Don't know exact temps as tractor doesn't have a temp gauge but you couldn't keep you're hand on the head for more than 10 secs. Change to another head and plough all day and you could keep you're hand in the head as long as you want

 

[Ley253]

Well, as the engine should run just below boiling point, I would think that its running too cold now! Is the same thermostat being used in both? Theres a chance that the "hot" head is scaled up internaly, slowing the coolant flow.Indeed if it is, that could have caused the crack, the reduced flow allowing localised overheating to take place, and a marginal area such as an exhaust port would be one of the first to suffer.
It might be an idea to get one of these remote infra red temp indicators, the are cheap enough, (E Bay is one place to look) and they do put your mind at rest, if you have any temp worries on a gauge free engine.

 

[Mydexta]

New thought

With original head on with good sealing at the valve seats the engine should have high compression, when the gasses are being compressed they will escape by the easiest route, which could be the rings which may not have bedded in properly or were possibly installed upside down, however with the other head the valve seats aren't as good so it could be losing compression there if the gasses are escaping into the exhaust port even when the valve is shut

Possible??????

 

[Ley253]

leakage into the exhaust port could happen, but I think you would have a pronounced misfire, especialy when cold. If the rings were in trouble, the engine would "breath " excessivly due to the crancase compression.

 

[Mydexta]

The tractor was breathing fairly heavy before I changed the head over . Today I did a mythbusters experiment and poured a soapy water solution onto the valve faces and over the crack. I then blew compressed air in both the inlet and exhaust ports where the manifolds go and had no bubbling on either valve or thru the crack
Thoughts now turning towards the rings

 

[Ley253]

Dont forget what I said re head gaskets. There are many out there whuch are no use at all, they do not fit closely around the "fire ring" on the liner top, so allowing compression to go down past the outside of the slip fit liners into the sump. A local man fitted new liners twice as he thought the first set were the cause of the breathing, he was lucky in that the second head gasket was a correct fit, coming as it did from a differant supplier.

 

[Mydexta]

When I refit my own head I will fit a new gasket, however when I changed the head I used the same gasket and didn't have any of the problems that I had before

 

[Mydexta]

Just seen this, didn't know there was one available as there are no empty holes In the dash for it. Does anyone know where in the system it would screw into
http://bit.ly/JUzSmR

 

[multi power]

its all very well pressure testing n the crack not causing problems but that may change at operating temp