Opinions......loud tapping

[johndemar]

It's finally cooled down enough here that the thought of driving the spider seemed like a good idea.
I hadn't started it in about a month and was surprised that it started after a few cranks. I set the hand choke and let it idle to warm up, but after running for maybe 5 minutes there developed a distinctive hammer on metal tapping sound.

I immediately disconnected the hand choke and the car returned to 800 RPM before I shut the engine down. The sound was RPM related as it decreased when the choke was turned off. Guessing it ran for 10 to 15 seconds before turning it off.

My ears aren't what they used to be and wasn't able to determine exactly where the sound was coming from. And I hesitate to start it again for fear of causing real damage.

My first thought was a connecting rod or bearing, but have no basis to prove or disprove that.
Here is what I plan on doing:
1. Drain the oil and see if it comes out clean or not.
2. Doing a compression test on each cylinder.
3. Check the cams, shims, and buckets are to spec.

I know it's not much to go on but I would really appreciate your thoughts on anything else I should check.
Car is a 76 with 54K original miles on it.

[So Cal Mark]

remove the spark plugs and find which cylinder has the debris in it, or check for an exhaust leak at the manifold

[johndemar]

Thanks Mark, I will do that. Won't have a chance to look until after work tonight.

[johndemar]

Guess it's human nature to assume the worst when it's usually something simple.

A cap socket that I used to plug the head when removing all of the pollution equipment on the number 4 cylinder backed out and was just laying in the spark plug well.

It's finally driving season in the Arizona desert...

[So Cal Mark]

whew! glad to hear about a minor issue and easy fix