I have a 1977 chevy 1/2 ton 4wheel drive stepside shortbox with a 350 4 barrel holly with headers on it and auto trans. I had to replace the distributer rotar today and when I was cruising I kind of gunned it, acceleration is fine however soon after my tranny kicked down and my engine was at higher rpm it popped from the carb once and then the engine proceeded to run fine. I did this several times, same popping etc. So I am pretty sure when I replaced my rotar I messsed up the timing. (I also gave it a tune up spark plugs oil etc for the first time, new truck to me) I was wondering what exactly is the proper RPM and what timing I should set it at? I notice alot of people say 12 degrees and work from there until it runs fine, but I just do not know. Any help please!!!!

 

If you only changed the rotor then you shouldn't have been able to alter the timing. Did you turn the distibutor when you did it? Easy enough to check it though. Do you have a timing light?