Well if it was a manual trans, I would have a better answer for you, but hmmmmmm. Ima guessing you looked for an exhaust leak already,so I'm kinda out of ideas.
It almost sounds like it's too slow to be crank-related, and it seems not to be in sync with the rpm in each gear. If it was crank related, we should be hearing it slow down to 59% on the 1-2 shift. Say from 4000 to 2400.
And too seems to be too fast to be in sync with the driveshaft.
So that just leaves the cam,which turns at half engine speed; so it would slow down from 2000 to 1180, on a 4000rpm upshift into second. Yeah that kindof sounds right.
Or maybe a header leak? which if just one port was leaking,would be at same as cam speed.
But man that is so sensitive to the gas pedal; have you got power brakes?And do they work properly? Have you tried disconnecting the Vcan?(I'm thinking diaphragm flutter, or not dropping out fast enough). What's your timing at the test rpm, say 2200? with and without the Vcan.
One thing I have noticed is that your carb is not responding properly to gas pedal inputs; almost like it's running very rich, at the test rpm and conditions.Yet it has a hesitation when slammed open,indicating lean on the accelerator pump.I'm trying to tie all that together, but it's not coming to me.......yet. Nice sounding mufflers tho, mine just scream when I get on it (Dynomaxers).
What carb?
So back to being at cam-speed......It doesn't sound like rocker arms,or valve train,and you said,IIRC, that it seemed to be coming from deep down in #8. So what's down there? Windage tray,oil pick-up,dipstick,collector,Tunnel pinchweld. What else? Pan evacuators?
oh.......trans dipstick tube. You got that secured?
