The dead cylinder would make the engine less able to try to spin against the friction. Friction of all 8 cylinders would be similar, but you have only 7 firing to overcome it. Analogous to how it would idle more poorly if you had just pulled a plug wire. (If you want to dig more into the theory you could look up terms like PV diagram, imep, bmep, fmep, thermal efficiency, and mechanical efficiency. I thought it was pretty cool stuff, but it's not everyone's cup of tea.)
The issue that "Myself" (it feels funny to say that word without actually referring to myself) was talking about is a huge increase in friction caused by component failures and metal wear particles getting into everything as well as a power decrease from those failures. My guess is that you don't have that issue, but as a quicker check, take a look at the oil and look for sparkly things. It's never a bad idea to check the filter, but I don't think I've ever cut one apart. I had an engine fail once, but I didn't need to look inside the filter -- all the burned bearing pieces and broken rods sitting in the oil pan told me that. ;-)
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Originally Posted by CCCC
This sounds ominous - and certainly will check for loose pieces if the idle problem can't be solved with carb work and zero vacuum leaks. What is the potential problem you are addressing - or, what happened in your case?
No one has spoken to the possible effect upon normal idle in the case of two non-working valves (one can dead). Any experience there?
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