The cammer has an internal drain at the rear of each head, they are only about 5/16, for the short time that my engine was running it seemed to drop
oil pressure as the RPM increased so my natural assumption was not enough
oil flowing back to the sump. The other issue is that the
oil pump is located at the front of the engine so this oil has to basically flow against g force of acceleration to make it back to the oil pump hence why I am running my return lines to the front of the sump. The return galleries in the block could possibly be made larger but I wasn't sure how much meat was around them so choose external returns. From what I can see with the cammer the main oil return is via the large hole at the front of the head, which is great if your in stop start situations but for periods of long acceleration or say and extended up hill grade then I couldn't see enough of the slippery stuff getting back to the sump to run around and do it's job properly.