Pull the valve cover , make sure the valves are opening & closing the same amount as the other cylinders. Set the engine on fast idle & see if 8 is firing then . Make sure there's no obvious vacuum leaks ( hose, etc.)
Will pull the valve cover and do that and report back. Will try fast idle as well. After I created the post I went on the hunt for a vac leak and found one, fixing the leak didn't change the misfire unfortunately.Pull the valve cover , make sure the valves are opening & closing the same amount as the other cylinders. Set the engine on fast idle & see if 8 is firing then . Make sure there's no obvious vacuum leaks ( hose, etc.)
Will pull the rocker cover and check.Inspect the distributor cap for carbon arc paths from that terminal to another or to ground. or the presence of moisture. Rocker cover off, carefully check the rocker movement in search of a failing lobe and lifter. Replace the plugs and gap them at .030 inch, even good looking plugs can go bad.
Will still do a leak down, just couldn't get to it today.It does kinda look like number 8 intake isn't moving as much. It's moving enough that that doesn't explain the dead miss though. It may run a bit rough but probably not a dead miss.
I'd do a leak down on number 8 at the very least to rule out a mechanical problems but this smells like an ignition problem.
Also. a spray bottle squirt on the headers tubes is a good way to see what cylinders are problematic. If the cylinder is working well the water evaporates in 1 or 2 seconds or less with a noticeable sizzle and if it's dead it'll stay wet for a more seconds. This doesn't work very well on manifolds though. Another way of checking for spark is to use your timing light on the wire as close to the plug as you can. Flashy's indicate a spark. No flashy, no spark.
What does the plug on 8 look like?
Yeah I have to admit I stared at that for a couple of mins really wondering WTF.Can't figure out how the shiny spot on the pushrods for 4 and 6 seems to be above the slot in the head. I guess the pushrods might have run with guideplates at some time.
Someone mentioned that to me yesterday so I backed out the idle mix screws, I could smell it running richer but it didn't fix the miss.i had a similar problem with my 460 in my motor home, #4 made absolutely no change when i pulled the plug wire, i could hear the miss from the exhaust, i changed valve springs, did a complete tune up on it and it was still there, it has a holley carb on it so i decided to adjust the carb a little, as soon as i turned the a/f mixture screw out a little the miss went away and the engine smoothed out, turned out to be a lean miss,
Could be #8 intake gasket sucked in and pulling crankcase air instead of mix.
I will try that test, since this is a smog car there is enough stuff to make pulling the intake a PITA but beats a bad cam.Could be sucking air in from the crankcase due to a sucked in gasket. Easy to check. Pull the PCV valve, and stuff a vacuum gauge in the hole.Plug the filtered air intake on the opposite side of the motor, on the valve cover.
If it builds vacuum its leaking from crankcase to intake runner.
If it slowly builds a little pressure, then it does not have an intake leak . Easy peasy to check.