Steve the green holes are steam holes to allow water in/out. After my research on re-routing the water supply by adding a stat and top hose outlet at the rear of the head and modifying the head gasket to provide equal flow across all cylinders (as far as i can measure), Im 100% that all the holes in the pic above are for either water or studs/bolts. The oil feed from the jackshaft hole feeds up to the head via one of the the front stud/bolt holes( as mentioned above). Ive done 1000 miles on my mod (no-one cared about ) so I can fit an inlet manifold without a stat housing hence my re-route. Soon to be fuel injected with OEM parts (Nissan). I respect your knowledge on Dolly's and car stuff in general and in no way am trying to argue, but I have done 12 months of work on the cooling system and know a lot more than I did before I decided to go the hard route (genetic
Tony G, you may well be right about the yellow holes, it's been a long time since I truly LOOKED at the underside of a Sprint head, other than to try and determine just where the blow was in the head gasket! But i'm still sure the green holes must be the oil supply, it has to get up there somehow! and i'm equally sure about the oval hole at the upper right corner being a drain, since the engine sits slightly lower at the back (only a degree or two, but it's enough) there must be a way for oil to escape the rear end of the cambox or it would build up disatrously, especially under acceleration!