1. Worn or damaged piston rings: Worn piston rings can allow oil to seep into the combustion chamber, where it is burned along with the fuel. This can cause excessive oil consumption and lead to oil deposits on the headers.
2. Worn or damaged valve seals: Valve seals prevent oil from leaking into the combustion chamber when the valves are closed. Worn or damaged valve seals can allow oil to leak into the combustion chamber, leading to oil burning and header deposits.
3. Leaking head gasket: A blown head gasket can allow oil to leak from the oil passages into the combustion chamber. This can cause excessive oil consumption and oil contamination in the cooling system. It is also a common cause of blue smoke from the exhaust, which you may or may not have noticed.
4. Faulty Positive Crankcase Ventilation (PCV) valve: The PCV valve is responsible for controlling the flow of gases from the crankcase back into the intake manifold. A faulty PCV valve can cause a build-up of pressure in the crankcase, which can lead to oil leaks and burning.
5. Excessive oil pressure: High oil pressure can cause oil seals and gaskets to fail, leading to oil leaks and burning. This can be caused by a faulty oil pressure regulator or a clogged oil filter.
If you have ruled out blow-by in the air filter or carburetor, it's still important to have the issue diagnosed and repaired by a qualified mechanic to prevent further damage to your engine. The mechanic will be able to perform a cylinder leak-down test, compression test, and other tests to identify the specific cause of the oil burning and recommend the appropriate repairs.
