i replaced the front cam/crank seal in my 1980 245 i went ahead and did a t-belt/water pump it was the next weekend before i was able to put it back together(lack of parts), the re-timing process came together rather nicely but when the engine fired up it knocked rather harshly, i turned off the engine immediately and after re-examining the timing marks and the piston it turned out my cam and distributor were off by a few degrees. does anyone know if the b21s are interference engines? did i just turn my cam seals into a valve job? any advice would be appreciated i love this old girl!