Mac, Having timing marks aligned with compression on no1 and then turning cam to opposing tooth𖐬o] will simply time no6 to compression stroke. Spark timing would then have to be timed to no6. It is possible to have timing 1 tooth either way and still run. Worn guides can fluctuate pointer rapidly at idle and smooth out with revs, carby problems will cause slow drift from 12 to 16 approx, it is hard to imagine car running at all at 8 to 10. If the fluctuation is rapid it is common to all cyls,if it dips every one or two revs it can be traced to a particular cyl[or two]. Weak springs will be normal⎞ to 22] at idle and fluctuate wildly at higher revs. This has gone on too long, the car should be taken out and given a darn good hiding. Respectfuully jack.