- A manifold coating in a tin, for a brush, rated to about 650°C.
- No primer, by instruction. POR-15 says it is incompatible with any, including POR-15's own Rust Preventive Coating.
- The cure is 24 hours of air drying, then 15 to 30 minutes above 150°C, and it reaches full hardness once it has cooled.
- It gives away 350°C or more to the two header aerosols, and asks for nothing like their bake.
- Frost imports the US pint; Amazon lists it under Frost's name.
What it is
POR-15 is the American rust-coating maker whose Rust Preventive Coating most restorers know, and High Temp is its coating for the hot parts: a brushable film for manifolds, headers and exhausts that POR-15 rates to 1,200°F. It is the product the company sends you to when you ask whether its Engine Enamel will take a manifold, because that one stops at 300°F.
It reaches the UK through Frost in the US pint, 473 ml, and Amazon UK lists it under Frost's name. The listing reviewed here is factory manifold grey; the brand page covers the single route by which POR-15 reaches Britain.
The figures, and what they mean
POR-15 gives one figure, 1,200°F, and converts it to 648.8°C, a precision no manifold will respect. There is no qualifier; VHT and U-POL call their figures intermittent, and the paint type page explains why that word matters. Read 650°C as the class the can belongs to rather than as a promise about the hottest spot on a header.
For a cast iron manifold on a road engine that class is enough, and POR-15 says nothing about stainless either way. For a header on an engine that is worked, the two aerosols rated above 1,000°C have the headroom this does not.
Putting it on
POR-15's directions start with its own cleaning route: Cleaner Degreaser worked into the surface, then Metal Prep to etch the metal and shift scale. On a rusty casting, blasting is what actually gets into the texture, and the preparation guide says what to plug before a part is blasted.
Then nothing. High Temp goes straight onto clean, prepared metal, and POR-15 states that it is incompatible with any primer or topcoat, including the company's own Rust Preventive Coating. This is the opposite of VHT's instruction for FlameProof, and the two systems must not be mixed.
Two thin coats, or three if the part will meet anything corrosive, each within one to 24 hours of the last. After 24 hours the previous coat has to be scuffed with 320 grit or the next will not stick. A brush reaches the back of a manifold that an aerosol mists past, and there is no overspray to mask against. Painting manifolds and exhausts covers the sequence for all three makers.
The cure
This is where POR-15 differs from the aerosols. It wants 24 hours on the surface first, in air, before any heat. Then 15 to 30 minutes above 150°C, which a domestic oven manages for a manifold on the bench or an idle run manages on the car. POR-15 says the coating reaches full hardness once it has cooled again.
The aerosol version of High Temp is stricter, at least two hours at 205°C, which is an oven job; the tin reviewed here is the brush grade and the gentler schedule is its own. As with every coating in the class, sudden high heat on a film that has not dried is what destroys it.
Where it sits against the others
Against VHT FlameProof and U-POL Raptor Flameproof: both aerosols, both rated above 1,000°C, both wanting their own primer. POR-15 is the one-tin job with the brush and the lower figure. Against the 650°C aerosols from Jenolite and the stove paints, it has the same class of figure, a written cure, and a maker who says in writing what not to put under it.
Best exhaust and manifold paints 2026 ranks it third and the best brush-on.
Who it suits
A manifold that is off the car anyway, on a bench, with a brush and a day to wait. Anyone who wants a factory grey rather than black. Anyone who does not want a two-can system: there is no primer to buy because none is allowed.
Not a race header, where the figure runs out. And not the impatient: a part brushed on Saturday is not curing until Sunday.