I just recently finished assembling and starting my 454 and am running into a strange problem. After getting the fresh rebuild running, I broke in the cam for about 20 minutes @ 2000 RPMís. I then readjusted the valves and set the timing @ about 16 degrees btdc. (I have a comp cams 268h extreme energy cam and this seems to be the best timing for it) The carb that I currently have on the car is a Holley 650dp with #68 jets on the primary side, and #72ís on the secondary side. Hereís my problem / question for everyone. When I start the engine cold it runs fine and idles perfectly. As the engine warms up the idle starts to get rough and the engine wants to die. Even if I bump the idle up or rev the motor it still stumbles and eventually dies. As it starts to die the exhaust note changes too, it goes from a clean solid low rumble to a raspy coughing stall.
When I first started trying to fix this problem, I thought it might be the HEI ignition system getting hot and dying, and since I had a spare module and coil sitting around I changed them out. That didnít fix the problem so I now suspect the carb is the problem. Since I need to go to a bigger carb anyhow I figure this is the next logical step, but I wanted to ask everyone for some advice first.
Sound like a carb problem to you guys? Whaddya think about the Edelbrock #1407 750cfm carb for my BBC?, or should I stay with Holley and get another double pumper. Only upgrade to a 750?