low power when hot?

[512Stroker]

Does this help?

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Now that we have a better view
For only 30 miles those plugs look very rich
Something is astray with your carb.
Cant see enough of the ground strap to comment on ignition timing.
This will help you
Spark plug reading can be complex and sometimes frustrating task this page will help make it easier and the results rewarding

 

[KosmicKuda]

I wouldn't be too unhappy with those but Number 2 and 4 cylinders have a problem!

I would definitely do a compression check to get a baseline. If they are all within 10%, I'd move on to changing the valve seals. You can do that with the head in place on the engine.