Ive been having a few problem with the minor engine recently. I previously posted a message about pinking which was solve by removing an excessive amount of carbon from the cylinder head and piston crowns. When i had the head off i removed the valves to give them a good srub to remove the carbon, i noticed that when replacing the valves into their correct guides where they had come from, they would only fully locate into the seats at a certain position with them having to be twisted slightly to find the correct location, otherwise the valve would get jammed about an half an inch above the seat. Is this indicative of bent valves sticking in the guide? The engine has continuously been lacking power and seemingly running slightly weak. Could this be due to this and worn guides. When i remove the oil filler cap on top of the rocker cover i can hear a pulsating air noise that is not mechanical from the tappets. Could that be the noise of air leaking from the valve guides i.e combustion and intake/exhaust. The head is a 3 year old unleaded head that has done approximately 15-25,000 miles. Any advice would be wonderful.
Hello M,
the valves should be free to drop onto their seats and if tight does not really indicate worn guides. Were the valve stems thoroughly cleaned, i.e there is not some carbon there that is stopping the valves seating?
Valves that do not close easily will give a very poor performing engine indeed. Given that the lubrication system is working correctly in the rocker area I would not expect any serious wear problems with such a small mileage.
I got the head from a specialistic moggie garage in bristol about 3-4 years ago. Im not too sure where they got it from but i believe it to have been a good quality source. I think some of the wear may have come from the excessive carbon, pinking and overheating that went with it. I certainly know that there is slight pitting in the valves and seats that should be easily ground out.
Happy New Year