Ernie, if it's ribbed and there are no numbers on the passenger side of the block (indicating which vehicle it was intalled in), it's probably a service block circa late 60's early 70's. I've also been told they tended to be stronger, and I have one cast in 71.
I'm running solids, with an Elgin Pro-Stock that calls for .025 int. and exh. lash. I have checked them and had others more knowledgeable check them every 1000, and I swear they don't change more than a hair, so I'm a little confused by some of the guidance above. But it is a mild street cam for a street motor....everything's nice and symmetrical
