Thanks for the reply. I seem to have hit a 6600 rpm wall and not sure what is causing it. it's not really a miss, more like a rev limit....it just seems to go flat, but not like it's the end of the power band.

the cam is a .904 intake lobe flat tappet with 150 lb. seat press. and what I think is good geometry (used a B3 rocker relocation kit) with Stewart 3/8 x .120 wall pushrods.

I'm at 13.3-1 gasoline. I have a 6A and tried a 6AL with no chip....still the same, tried various plug brands and heat ranges and gaps....re-did and added some grounds to both the engine and MSD...new tach (old one had a built in shift light)

I have an O2 recorder and when it hits 6600, it goes rich. I tried various jet/ bleed combos and they reacted as expected till 6600. next on the list is another distributor.....currently a stock one I've used for years up to 7200 in previous engines, but they weren't as high compression ratio.