64 C10 Engine Ticking Sound Help
 

I started up my truck the other day and it has this awful ticking sound coming from the engine. I think it is part of the valvetrain but I am not sure. Any ideas of what it could be? Engine is a 1978 250 inline six.

Video of engine idling
https://www.youtube.com/shorts/hxsebdoDo-Y

Re: 64 C10 Engine Ticking Sound Help
 

sounds like a rocker arm ticking, pull the valve cover and look to see if you have bent pushrod, may just need adjusting. Did it start suddenly or get progressive louder

Re: 64 C10 Engine Ticking Sound Help
 

Sounds like a collapsed lifter!

Re: 64 C10 Engine Ticking Sound Help
 

You can pull the valve cover and run the engine without making too much of an oil mess. I’d pull the valve cover and look for loose rockers or stuck valves. Sometime a good dose of Marvel Mystery oil added to engine oil will loosen up a stuck lifter. Does it look clean or dirty if you look in the oil filler hole?