I have a 12 cylinder diesel engine. After dismantling we found that all the exhaust valves are bent. The valves are completely operated mechanically. What could be the reason for this?

The old rule was to change the engine oil when 50% of the new oil TBN had been consumed. Because of the virtual absence of fuel sulfur today, much less is needed. Chevron now sets the TBN guidelines for all of its diesel engine oils as follows:FOR ALL OILS when using ULSD• Severity 1: 50%-44% of new oil TBN or 3.5 to 4• Severity 2: 43%-36% of new oil TBN 348 to 2.9• Severity 3: <35% of new oil TBN < 2.8 to 2• Severity 4: less than 2 <2Other parameters of engine oil are now more important to engine durability and extended service protection than TBN. These are parameters such as oxidation stability, wear control, effective soot dispersancy. A balanced oil has multiple performance abilities and TBN is only one of the performance measures that are important in today’s high performance engine oil.

higher TBN is not always good for the engine it depends on the diesel if it is high sulfer or not in normal conditions use the regular TBN rate so u wont have resdue

MR. Ajmal

The main reason for your problem is the contact  of the valves with the pistons due to the incorrect timing chain, check the serviceability of chain.

I hope you can solve the problem with the lowest cost.

Best regards.

Hello, thank you for your question, first thing I need to know what is the engine brand, and the operating condition before the engine stops, what is the type of valve timing mechanism, Any how the most common reason is the failure of timing synchronization, overheating and damage connecting piston bearing and main crankshaft bearing damage. I hope this will make you satisfied Regards Jamal Qishawi