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What should a valve look like after lapping?
Both faces should be a dull grey when you’re done, with an even width across both faces. The ring doesn’t have to be in the dead center of the valve, just a nice even ring around the valve. Although some seats may need two or three times of lapping, it is not necessary or good to over-lap the valves.
Do valves seal themselves?
Bad valve stem seals, will show themselves during; prolonged idling at stop signs or stop lights in congested city conditions. The high vacuum, attracts oil in the heads to congregate around the valve stems. Upon acceleration, the oil gets sucked, past the seal and down through the valve guide.
Can a intake manifold leak cause overheating?
Engine overheating is another symptom of a possible issue with the intake manifold gaskets. A coolant leak will eventually lead to engine overheating when the coolant level drops too low, however there are instances where overheating can occur without any visible leaks.
How do I know if my valve seat is hardened?
A lot of times it is very difficult to see them once a head has been run. What you are seeing is probably just a machinig mark from when the valve seats were cut at the factory. I would look at the date code on the heads. If they are 1973 or newer, they should have hardened seats.
Is it bad to lap up exhaust valves?
When you clean up your valves during the rebuild process, even though you may keep the valves in the same positions, lapping is not a bad idea to promote better sealing. Overheating… I agree has nothing to do with the components that do the “breathing” of the vehicle.
Can a leaky intake valve become a burnt valve?
Under normal use (non-performance type use), the valves, both intake and exhaust, should last the life of the engine. If and when they do leak, it will not take long for the valve to become a burnt valve.
What happens if you have a leaky exhaust valve?
A proper flush 9/10 will eliminate the clogged jackets. A leaky exhaust valve means the valve is not closing properly, failed compression stroke and a burnt valve. In some engine types, this burnt valve and the piston can hit bending the valve and causing major engine damage.
Can a head gasket cause an engine to leak?
If it is with the head on the block you may be leaking elsewhere besides around the valves. Rings or head gasket maybe. Could even be a small crack somewhere depending on how abused the engine was. Were any valves replaced? if not are they stretched or bent?