I have just been looking at VHT paint curing temperatures. Generally header pipe and manifold temperatures will be sufficient, but if you want to coat colder surfaces then often oven curing is necessary: Examples:
VHT Flameproof (Silica-Cermic Coating):
- Paint must be completely dry before curing
- Heat to 250°F (121°C) for 30 minutes
- Cool for 30 minutes
- Heat to 400°F (204°C) for 30 minutes
- Cool for 30 minutes
- Heat to 650°F (343°C ) for 30 minutes
VHT Engine Metallic and VHT Engine Enamel- looks interesting as the cure temperature is lower:
- Bake at 200°F (93°C) for 20 minutes.
- The inherent heat of engine operation will also accomplish curing.
Hycote VHT Coatings (UK):
At 160 °C Curing Time = 100 minutes
At 190 °C Curing Time = 50 minutes
At 205 °C Curing Time = 30 minutes
At 220 °C Curing Time = 20 minutes
At 230 °C Curing Time = 8 minutes
Hycote could be an issue on the engine casings because they do not get hot enough.
Halfords VHT in the UK is not suited for mufflers so certainly will be a problem on engine casings, barrels and rocker covers may also be an issue???
I conclude that you need to choose a VHT paint that has a suitable cure temperature for the application you need. A few months back I recall someone on this forum measured engine temperatures and this data could be useful in choosing paints but I cannot find the thread. Based on a wet finger I know the head gets above 100 Celcius, but I do not think the engine casings and rocker cover get up to 100 Celsius. The barrels are probably close to 100 Celcius or sligthly over. I am sure the data is out there.
Edit: I meant to say that if the engine is completely striped down then those components coated with VHT paints with the 93 Degree Celcius cure temperatures could be baked in a domestic oven.