I think they are motorhome heads with extra cooling capacity around the exhaust valves. They are good to port and are like 452s when ported. They may have hardened seats, I'm not sure on that. Gary H. Sean B wrote: > Anybody know what "213" big block heads are? I've found a set. They > are open chambers. ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html.