A few annoyances - need tips: temp gauge, tapping under load, and a potential vapor l

[greywurm]

Have a 72 SBC 350 in my 71, pretty stock.
Hugger headers, HEI, aftermarket intake, edelbrock 1406 carb.
Mileage unknown, but the guy I got it from said it had roughly 8000 since last rebuild as it was in a show quality 53 3100.

Temp gauge:
If running it in park, stock gauge works fine. Needle raises normal, drops when the efan kicks in. But when I'm moving, it will drop all the way down and not raise until I'm at a stand still long enough. I thought maybe I should reinstall the sender since I didn't put it in all the way - used thread tape and was concerned about cracking the manifold. Reinstalled it without tape and some anti seize so it can come be removed down the road without issues. Problem persists.

Tapping:
I've pretty determined its around the passenger head. Only really noticeable when the engine is under load. Pretty quiet at idle. I removed the valve covers this morning and adjusted the valve lash, but the tapping noise continues... Read somewhere it could be loose headers or bad gasket?

Vapor lock:
New mech fuel pump, have an inline clear filter between pump and regulator. Get a consistent 4-5 lbs fuel pressure between regulator and carb while running. After I shut it off, I can watch that gauge slowly drop to 0.
Hot starting or even cold starting in the morning, she'll fire right over and stall out after a second. 3-5 seconds of turning the key, it will fire right up (usually I pump the gas once or twice). Makes me think of vapor lock, but the rubber fuel hoses I think are far enough away from the exhaust header.

What do you all think? Need some ideas...