SIDE VALVE - STICKY EXHAUST VALVE
Posted: Mon Mar 04, 2024 7:32 pm
I have recently rebuilt my side valve MM engine. It's been running so sweetly since getting it fired up and I couldn't have been happier.
However, yesterday, the engine all of a sudden started misfiring when pulling away from a roundabout. A quick roadside test and some spark plug changes ascertained the problem to be due to a lack of compression on cylinders 1 and 2, rather than a lack of spark. Fearing head gasket failure, I had to get the car recovered home, which spoilt an otherwise brilliant day.
On getting home, I tested the compression and it was nil on cylinder 1. I took the cylinder head off and (to my relief) discovered the problem was not the head gasket. However, the lack of compression was due to the fact that the exhaust valve on no. 1 had stuck open on this cylinder. Light pressure with my finger caused it to ping back into place. (Given that the engine seemed to definitely not be firing on cylinder 2 when I tested at the roadside, I wonder whether the valve also stuck open on this cylinder and then snapped shut by itself. I can't prove that for definite though.)
The engineering firm which I have used before fitted the valve guides and valves, and I remember them saying that they had checked and ensured that the clearances between the stems and the valves were adequate/correct. However, I am now concerned that this may not be the case. Could anything else be causing the issue? Was it just bad luck and is it likely to bed in and therefore not repeat? Is there any kind of lubricant I ought to apply to the portions of the valve stem that slide up and down in the guide to help prevent it from happening again? I will be absolutely gutted if the whole lump has to come out again... I have worked so hard and from I can gather it is nothing that I have done.
I would appreciate your advice. I'm trying to remain optimistic.
However, yesterday, the engine all of a sudden started misfiring when pulling away from a roundabout. A quick roadside test and some spark plug changes ascertained the problem to be due to a lack of compression on cylinders 1 and 2, rather than a lack of spark. Fearing head gasket failure, I had to get the car recovered home, which spoilt an otherwise brilliant day.
On getting home, I tested the compression and it was nil on cylinder 1. I took the cylinder head off and (to my relief) discovered the problem was not the head gasket. However, the lack of compression was due to the fact that the exhaust valve on no. 1 had stuck open on this cylinder. Light pressure with my finger caused it to ping back into place. (Given that the engine seemed to definitely not be firing on cylinder 2 when I tested at the roadside, I wonder whether the valve also stuck open on this cylinder and then snapped shut by itself. I can't prove that for definite though.)
The engineering firm which I have used before fitted the valve guides and valves, and I remember them saying that they had checked and ensured that the clearances between the stems and the valves were adequate/correct. However, I am now concerned that this may not be the case. Could anything else be causing the issue? Was it just bad luck and is it likely to bed in and therefore not repeat? Is there any kind of lubricant I ought to apply to the portions of the valve stem that slide up and down in the guide to help prevent it from happening again? I will be absolutely gutted if the whole lump has to come out again... I have worked so hard and from I can gather it is nothing that I have done.
I would appreciate your advice. I'm trying to remain optimistic.