valve's rattle
Be careful, a domed 400 does not like pump gas at all. I know I learned the hard way. I just love to bulid the 400 block's. About 12 yrs. ago I had one detonate sooooo bad that I could take a pencil & lay it between the bore's. Remember, the wall's are thin to start with. Especially today's pump gas, it's awful. If the picture you have w/ you're post is what you are running I would reccomend you to get a drum of 110 purple gas. It will be cheaper then replacing part's. At least try a few gallon's anyway. Kris