I've had my CRT hei for a couple years now. And I have the same problem. The low end and midrange performance is great. And I have smooth idle. But the top end it's a dog.. I have 3.54 gears, sm465, weber 38, hedman headers, Dui live wires. And when I'm in fourth at cruise and punch it to accelerate... It just sort of gets faster after awhile.
I know it's not the weber, I have that thing tuned perfectly thanks to Swatson454! Hey Shawn it's been awhile!
So what can I do? My grasp of how distributors and timing isn't very strong. I think my 258 runs strong everywhere except top end, it's not real comfortable going over 65mph power wise at all. And it seems I could be getting better mileage, I get around 15-16mpg
But it does tow pretty good, twice a year I tow a trailer with an Atv, Dirtbike and full camping gear, that trailer must weigh 2000 lbs fully loaded.
Any suggestions on where to start?