I have a 4150 (750)double pumper that I just took off my small block to start my 454. It runs ok but I have to keep the rpms above 1200 for it to stay running. Can anyone give me an idea of what to put in this carb for jets to at least get it to idle. The 454 has approx 500 hp. I don't want to drive it I just want to get it to idle so that I can move it around the yard to do some other things that I have to do. Also has anyone had any good or bad experiences with the 870 street avenger. thanx. wnk.

I would say you have a vacuum leak somewhere. There really isn't that much of a jetting change needed. The bigger the motor the stronger the signal to the carb so it automaticly increases the fuel flow.

Ditto what Oger said. Its a vac leak I bet. Check the power brake booster, PCV, vacuum modulator, and any other vacuum hose fittings you have. You can disconnect them one at a time and try plugging them - if the idle smooths out you found the culprit.

You can also try spraying carb cleaner around the base of the carburator (especially by the throttle shafts). Carb cleaner will smooth out the idle for a second if you hit a leak spot with it.

As a last resort you might try changing the intake manifold gasket. If the gasket blows out around one of the ports it can make a bad vac leak.