We've all seen that look. How clean do you want It?
I've had fair luck with the engine cleaner stuff at the do it yourself carwash. I disconnect the battery and cover it with a plastic bag. I'm also carefully to avoid spraying ignition components with the high pressure spray.
There are spray on foaming engine degreaser at places like Advance, AutoZone, ORielly's, etc. I've used those also with pretty good success.
Purple power works when mixed with a liberal amount of elbow grease. Dawn dish detergent might also work.
I'm usually happy to just get most of the loose dirt and more than half of the grease and oil removed. If you want it "show quality clean", prepare yourself for a bunch of work, including removing parts to access the smaller nooks and crannies.
The ultimate for an engine that old would be a complete disassembly, clean everything and repaint as you re-assemble.
Sent from my SM-G920V using Tapatalk