- A manifold coating, not an engine enamel: rated to 1,093°C intermittent, and for headers, manifolds and exhausts only.
- Two VHT documents, two figures for the last bake stage. The product data sheet is the one to follow; this page says where the product page differs.
- The cure is the job. Uncured, it marks under a fingernail and wipes off with solvent.
- VHT says it will not bond well to stainless, and that aluminised and galvanised pipes must be blasted first.
- One VHT can is 312 g, the American 11 oz fill. A 400 ml can on the same shelf is someone else's paint.
What it is
FlameProof is VHT's header coating: a silicone-ceramic film that survives the temperatures a manifold reaches, which its Engine Enamel does not. VHT is a Dupli-Color brand owned by Sherwin-Williams, and in the UK trade "VHT" has become loose shorthand for any very high temperature paint, so the first thing to check on a shelf is the can. The brand page explains the two products and the look-alikes.
It reaches Britain through restoration suppliers. Frost imports the 312 g can and it is Frost's import that Amazon UK lists, under FROST or VHT depending on who is selling it that week. The listing reviewed here is flat white; the colour on Amazon UK changes, and the sheet is the same for all of them.
The figures, and what they mean
VHT gives FlameProof a range, 1,300 to 2,000°F, which is 704 to 1,093°C, and calls it intermittent. A range covers a family of colours and conditions, and an intermittent figure is a peak the film survives for a while rather than a temperature it sits at. The paint type page sets out how to read ratings like this one. For a manifold on a road engine the bottom of the range is already more than it needs; for a header on an engine that is worked, the top of it is the margin that the 650°C class does not have.
Coverage is stated, which is rare for an aerosol: 12 to 14 square feet, a little over a square metre, which is a manifold and a downpipe with some left. It is touch dry in an hour and can be handled in three. The finish is flat.
The one thing the two VHT documents do not agree on is the last stage of the bake. The product data sheet says 315°C; the product page says 343°C. Neither is reachable in a domestic oven, so at home the last stage happens on the car either way.
Putting it on
The sheet wants bare, bright metal: scuff or sand until the metal shines, then wipe with grease and wax remover. On a rusty cast iron manifold that means blasting, because nothing else gets into the texture of the casting. The preparation guide has the general method.
Then VHT's SP100 FlameProof primer, by instruction. This is where VHT differs from POR-15, whose High Temp is incompatible with any primer, and the two must never be mixed: choose one maker's system and follow it to the end.
Spray between 60 and 95°F, which is 16 to 35°C; the Celsius figure printed beside the lower limit on the sheet is a misprint. Shake for a full minute after the ball moves and ten seconds more for every minute of use. Hold the can 20 to 25 cm away and lay on two light coats and one medium wet coat, ten minutes apart and all within an hour. Miss that hour and the sheet says to wait seven days before adding more, because fresh solvent on a part-cured film wrinkles it. Painting manifolds and exhausts walks through the whole sequence.
The cure
Until it has been heated properly, what you have sprayed is ordinary soft paint. VHT's words are that FlameProof only attains its properties after correct curing.
Off the car, from a completely dry film: 121°C for 30 minutes and cool for 30; 204°C for 30 minutes and cool for 30; then 30 minutes at the last stage, 315°C by the sheet or 343°C by the product page. On the car: idle for 10 minutes and cool for 20; idle for 20 and cool for 20; then drive normally for 30 minutes and let it cool. The guide draws both.
Expect smoke and a sharp smell the first time it gets properly hot. That is the resin finishing its cure, and it passes. Bubbling or bare patches afterwards mean the film was too thick, the metal was not clean, or the heat arrived too fast. If you fit a freshly sprayed manifold and drive straight off, the heat arrives too fast.
Where it sits against the others
Against U-POL's Raptor Flameproof, the other coating on Amazon UK rated above 1,000°C, the differences are the surface and the cure. U-POL's sheet lists stainless steel among the metals it goes straight onto, where VHT says FlameProof will not bond well to stainless pipes. U-POL's cure is one hour at 150°C or an idle run and a normal run; VHT's is three stages. VHT publishes the higher figure and the coverage.
Against POR-15 High Temp, the brush-on at about 650°C: POR-15 forbids a primer and VHT requires one, and POR-15 cures in a different order, 24 hours on the surface first. Against the 650°C aerosols from Jenolite and the stove paints, FlameProof has 400°C of headroom and a written schedule.
Best exhaust and manifold paints 2026 ranks the five.
Who it suits
A cast iron manifold, a mild steel downpipe or a set of headers on an engine that gets worked, where the owner will do the bake or the idle cycles before the first drive. The SP100 primer is another can and the cure is a morning; that is the cost of the figure.
Not a stainless system: read the warning on VHT's own page and buy the U-POL instead. Not a part that cannot be heated afterwards, which will never cure. And not an engine block or a rocker cover, which take an engine enamel and never see the temperatures that cure this.