thanx in advance for any help. I have a 69 Z28 with a zz4 350. problem is that it fires into the headers from cylinder #8. if I pull #8 plug wire it stops the misfire so I know it's #8. I have new rotor and cap and plug wires since problem srarted. Have adjusted the hydraulic lifters. compression is oK, timing is OK. had heads ported/polished etc. last summer and it ran fine after that. how do I diagnose a bad hydraulic lifter or a valve that is hanging up on me?