Im going to be painting my engine compartment and wanted something thats going to last a while. I know ive seen some post on it but i was going to por-15 the whole compartment and then top it off with the por topcoat paint. Does it need theprimer in between? How does this work compared to a quality regular paint?

According to their directions, you do not need to prime between the POR-15 and the POR topcoat. They claim that you need to use their tiecoat primer if you plan on using a topcoat other than theirs, but I've seen many posts here that say to scuff the POR-15 up with a scotchbrite pad, then topcoat with your choice. I spoke to one of their reps about topcoating POR-15 with 2K primer, and they said to scuff it up with 600 grit and go. As for the quality, I can't say because even though I've had it on my car in places for a couple of years, it has not been exposed to the elements at all.

I used POR-15 on my swamp cooler a year ago because the bottom was rusting out and man that stuff works great. Pay attention to their instruction, use the gloves even though they are a pain in the arse. I took the gloves off because they were sticking to the paint and then had black POR-15 stuck to my hand for two weeks.

Nick

Ive always brushed the por on everything ive coated and while it worked great and looked good i want a beautiful smooth finish by spraying it and wasnt sure if a regular paint would spray on and look better.

I've brush painted the POR-15, scuffed with a Scotchbrite and sprayed the Chassis Coat with very nice results. I think the direction say the wait for the POR15 to tach the spray the Chassis Coat but after two coats of POR15 3-5 hours apart the day get long so I wait 2 days scuff and paint the Chassis Coat.
This also gives me a chance to sand out any runs which I have never been able to avoid with brush painting POR15. I take a fresh razor blade, cut off the drip, sand, scuff the rest, and Chassis coat with great results.

Trooper