Tapping on top of engine

In relation to the noise when it idles down. It almost gets totally quiet but when I press the gas it started knocking and ticking how can I check oil pressure in top where do I attach gauge I changed out the oil pressure regulator with no help I don't want to tear it down if other things I could check thank you for all answers need to get fixed help.

Okay, thanks for info. I checked oil pressure at idle it was 58 psi isn't that a little low? I'm still debating tearing it down so all feedback I get us helpful.

No got another probably silly question. When we took off the cam the valve tappets came out. Cleaned them up but didn't get back in n original have so that could be a problem. I have got a used head should I go ahead and tear it down and put different head on and buy new tappets and maybe solve knock problem?

Okay, I'm sorry didst tell you I'm am looking at my options motor is still together. But it still has a knock don't know if its valve train or what. I have a head got from junk yard was thinking on tear down replace head and valve tappets hoping to quiet down the knock. Originally was driving over mountain pass when car suddenly shut off. Had it towed
troubleshoot it and found chain had broke so I replaced chain and guides and sprockets. Put back together and it now had a ticking noise which found was in chain. So fixed that and then started to get knock. So I thought oil pressure problem had 58 psi on top. Still knocking but it started nice idles good but makes that darn knock. So I'm asking at this point where should I go with it? I'm sorry about the long story but we can get on the same page. Thanks for all information I received.

Okay, I got a stethoscope from hf put it on top it sounds like it coming three tappets put on end of motor chain is not slapping. But I can hear the cam to tappets and valves but it has a noisy one on intake and one on exhaust no if I bent a valve it wouldn't run smooth either right so what should I do?