If the engine will spend a lot of time exposed (car shows, or maybe it's in a T-Bucket) POR-15 might be a poor choice. Unless you use a secondary topcoat. POR-15 is sensitive to UV (sunlight) rays. Not slamming it, I think it's a great product. But they are careful to tell you to use it in applications that are nto exposed to UV, unless you topcoat over it.