I'm stumped, valvetrain noise on startup? (with video)

[1968 Falcon]

I'm just wondering if anyone has an idea of whats happening inside of my engine. I have a 1968 Falcon with the 200 ci 6, and if I start the engine when it's cold there will usually be valve train noise ranging from a small tick up to a full loud knock. Over the course of about two minutes it will get progressively louder until all of the noise suddenly stops, the tick may start again once or twice, but generally from then on the engine runs perfectly quiet. The noise won't come back again until the engine is cold. Also, if I stop the engine and restart it the ticking will stop (if I almost kill it with the clutch it does the same thing).

This engine has about 140,000 miles (maybe +100,000 I don't know) doesn't burn any oil, and I've managed to tune it so it gets 31mpg on the highway.

Could it be something related to oil pressure? I just don't know since it isn't persistent.

Here's a video of it happening.

http://youtu.be/EQeY4kKEtvw

It would be great to hear any ideas or what I need to do to fix it.

 

[Econoline]

Maybe a bad lifter. I'd pull the valve cover, run it and have a look see as to which one it is. If you can't tell, shut it down and push on each rocker at the pushrod end and see if one has alot of play. Do you have an oil pressure gauge? If the oil pressure is dropping then coming back it could be a problem with the oil pump, like a faulty/sticky pressure relief valve.

 

[JackFish]

why did you leave the hood closed for the video?
It might help if it was open and you moved around with the camera to help locate the source of the sound.

 

[1968 Falcon]

Thanks Econoline, I'll have to try what you suggested when I get a chance. I'm still pretty new to the internals of my engine, I know the basic functionality of things, but not how to see a problem, so that helps. I could also see it being the pressure release valve sticking in the oil pump because of how sporadic it is. It seems like shutting the engine off would lower the pressure enough to make it close if it was stuck open. I don't have an oil pressure gauge, I should get one.

JackFish, I videoed with the hood down because its harder to hear the knocking over the fan noise and other engine sounds when the hood is up. But the sound does come from the top end, generally around the # 2 cylinder as far as I can remember sitting here.

 

[bubba22349]

Yes it could be from low oil pressure, sticking valve lifters, or the oil pumps pressure relief valve, a good first step is to hook up a good mechanical oil pressure gauge to the engine to see what you have now and if it changes during operation. If the engine sat a long time without use or wasn't maintained properly i.e. With regular oil and filter changes. If you just don't know about its condition or the maintenance it had you might do an engine flush and then change the oil and filter after awhile and a few changes over time you can get the inside cleaned up and may also free up any sticking parts before tearing into the motor. If you can find JB products (Justice Brothers) in your area or online, they do have a very Good engine flush. Good luck