Take a look at the timing to make sure it is ROCK SOLID in and out of gear.
Look into the carb at idle speed and check for nozzle drip. If you have nozzle drip you will need more bypass air and/or more idle fuel to the mixture screws.
No big secret here that I am NOT fond of tight LSA camshafts with a lot of seat timing for street engines.
I get more complaints from folks who go that direction than any other. The Thumper and Thump your Mutha stuff tops the list, followed by the Comp XE cams. Hardly a day goes by someone doesn't call here bellyaching about rough idle, doesn't want to stay running when placed in gear, or the wife woln't ride in the car now that the new engine is in place because it stinks her hair up!
On a more serious note, I get involved in a LOT of big CID "stroker" engine builds, and FAST Class set-ups. Over the years the wider we've gone with LSA the quicker the cars are at the track and milder and easier to manage on the street.
I attached a dyno sheet below showing how this works. The first cam was purchased after the engine builder called Comp for a recommendation. The XR276HR is a very popular hydraulic roller cam from their catalog.
The ONLY change I recommended to our customer after everyone at the dyno shop right down to the janitor was blaming the Q-jet for the piss-poor power production of the fresh 455 engine build and some pinging when they tried to crank up the timing to make more power.
I told them to leave the carb alone and change the cam, and provided the specs. The new cam idled better, improved throttle response, broader power curve and made more power as well.......Cliff
