VHT Engine Block Primer Paint Light Gray This VHT engine primer is heat resistant up to 288 degrees Celsius, making it ideal for painting the engine block. The primer is essential to obtain a quality and more durable paint over time. NB This primer does not need to dry before you paint over the colored paint. It is important to paint all layers in one session in maximum 1 hour, with a rest of 5-10 minutes per layer.