With a manual trans, if I run the usual 12>14, the engine will start to buck, as the rpm falls.. Carb-wise, I have tried everything to get it to run down there and nothing worked.
I am familiar. Can you say what it is that causes that bucking behavior? Something is causing a come-and-go situation, but what is it? Centrifugal? I missed your earlier comment. Got it.
In reply to other items mentioned:
Current engine was put together in the early '00s. Likely to have less than 5K miles on it. Don't recall the valve spring PN, but it was what Hughes recommended for my 'kit'.
Top rings are CA Gapless (was 'cool' at the time) with a plasma/moly 2nd. Pistons are JE (I think?), moly coated. I too run 5-6 quarts of oil in a 7qt. pan. Something niggles at me that I left the windage tray off. Something to do with not fitting with the crank studs maybe. Not sure. I do run Valvoline 20W/50 with a high volume pump. Give me Zn&P please. Water pump is an anti-cav Milodon. I tried a smaller (than stock) crank pulley. Certainly had charging issues and IIRC cooling went south, too. Took it off. 30lb. flywheel for giddyup. When I raced the car, I ran 5:13 gears, so flywheel inertia was not relevant. I run GL4 in my 833. I'm not doing much in the way of 5500RPM shifts these days, so want to err on the side of longevity. I LIKE an ATF fill in the trans, but don't trust it for the long haul. ...not that my car does much of that!