I have already prepared the engine for paint so, it is now time for actually painting the Mazda MX-5 engine. I have been waiting to do this for a while, but I was determined not to rush the preparation stage, as getting that right will make the painting actually last and give a much better result.
Paint Used
Now, there are lots of options for painting engine blocks and many YouTube videos walking you through the process in detail so I was able to do a lot of research quite quickly.
The first thing to say is you need to use a High-Temperature paint which is designed to cope with the heat cycle of an engine block. Typically most engine paints have a heat range of 150-300degC. You can get paints that can cope with much higher temperatures (+1,000degC) which can be used on exhaust headers etc. This extreme temperature range is not needed for an engine. Here are the 2 main paint options that both had good reviews and kept coming up time and time again in my research.
POR15 Brush on Paint
POR15 paint is a brush on paint direct to metal. They recommend for the best results, to clean the engine first with POR15 Cleaner Degreaser then etch metal surfaces with POR15 Metal Prep. They have a range of colours and the paint is good for up to 150degC so perfect for engines.
In the UK I found the Frost.co.uk website as an excellent source of specialist paints. Their prices (as at March 2022) are:
- POR15 Engine Enamel Paint 473ml – £30.
- POR15 Cleaner Degreaser (Marine Clean) 3.78 litres – £29.
- POR15 Metal Prep (Prep & Ready) 946ml – £24.
A single can of the POR15 is enough to do the engine, but I also wanted the same paint colour for the gearbox and differential so I would have needed 2x cans of paint so £60 in total.
VHT Spray Paint
The VHT paint is spray paint with a 3-part system consisting of primer, colour enamel coat and clear gloss top coat.
Their prices (as of March 2022) are:
- VHT Cast Aluminium Engine Enamel High Temperature Paint (312ml) – £12.
- VHT Light Grey Primer for Engine Enamel High Temperature Paint (312ml) – £11.
- VHT Gloss Clear Engine Enamel High Temperature Paint – £11.
Now, a couple of cans are needed to do the engine and I wanted to also paint the gearbox and diff the same colour. So, I would need about 4 cans of each by my estimates so £136 in total.
Paint Chosen
I ended up deciding to go with the VHT 3-part paint system, despite it being the more expensive solution. I felt that the primer coupled with the gloss top coat would give an overall better finish and hopefully provide better durability for the paint. It would however take more application time due to each of the 3-parts needing 2x light costs and a medium wet top coat.
Paint Process
I was ready for painting the Mazda MX-5 engine in February. So, the weather conditions were not ideal to paint the engine outdoors. I decided to set up one end of my garage as a paint Booth by hanging up dust sheets to create a separate section.
I then used a 2kW heater to get that space up to a decent temperature of 25degC. Considering it was about 8degC outside this wasn’t bad at all. I think it helped to get the correct adhesion of the paint.
Next, I warmed up the can of primer by placing it in a bowl of hot water for 5mins. This I read also helps with the paint adhesion.
The final thing I did was another clean of the entire engine block with Holts Brake Cleaner and a paper towel. This was to take off any last remanence of grease. I wore nitrol gloves to make sure I didn’t leave any grease from my fingers.
I then followed the directions on the can for time to allow between coats which were:
- Primer – 1st light coat > wait 10mins > 2nd light coat > wait 10mins > medium wet coat > wait 30mins before emamel colour coat.
- Emamel Colour Coat – 1st light coat > wait 10mins > 2nd light coat > wait 10mins > medium wet coat > wait 30mins before clear gloss coat.
- Clear Gloss – 1st light coat > wait 10mins > 2nd light coat > wait 10mins > medium wet coat > wait 30mins before taking masking tape off.
So 9x coats of paint are needed in total. The engine was mounted on the engine stand. I also had several smaller engine pieces (throttle valve, oil pump and thermostat housing) which were set up in a smaller paint area. I set to work.
Personal Protective Equipment
Here is a list of the PPE I used:
- Nitrol gloves;
- Goggles;
- Cannister face mask.
Ideally, do this painting in a well-ventilated area or outside. The fumes from the VHT paint are particularly potent. I had a dilemma, if I opened the door to get better ventilation it would drastically reduce the temperature of the paint area. If I kept the door shut the temperatures would be much better but higher fumes. I went for the latter and chose to ventilate well after I finished. I wore a very good canister paint mask which did an excellent job at minimising the fumes I breathed in.
Photos of Paint Process
Reflection and Summary
I was really pleased with the end result of painting my Mazda MX-5 engine. The finish I managed to achieve in the end was really great. It did however take several days to stop my house from smelling of paint after I finished. My garage is integral to the house. While I contained the fumes to the garage, they seeped through the roof into the room above which wasn’t brilliant. It also generated a lot of paint dust in the process. Even outside of the dust-sheeted paint booth there was a thin layer of dust on everything.
On reflection, if I had used the POR15 brush-on paint, I don’t think it would have generated anywhere near this amount of fumes. It would have been completed probably quicker and wouldn’t have generated the layer of paint dust on everything. I do think the VHT paint is likely to be a better overall finish and likely more durable. However, by how much in reality I don’t know.
If doing this again in my situation I think I would either go for the POR15 brush-on paint system instead. Or I’d ensure that I applied the VHT paint in warmer weather outside or in the garage with the door open.
Video of Painting
Summary of Build Costs and Hours
Here is a summary of the costs and person hours (total number of hours for every person that has helped) for the build so far. This should hopefully help others with the planning of their builds, by providing cost and time actually incurred for this build. A more detailed breakdown of all the costs and hours worked on the build to date can be viewed here.
| Person Hours Worked This Post | |
|---|---|
| Engine Paint - 3x coats primer, 3x coats silver, 3x coats clear gloss | 7 hrs |
| Car Build Costs This Post | |
|---|---|
| VHT Primer Paint 400ml (x4) | £46 |
| VHT Silver Paint 400ml (x4) | £46 |
| VHT Clear Gloss Paint 400ml (x4) | £46 |
| Totals | This Post | To Date | All Posts |
|---|---|---|---|
| Person Hours Worked | 7 hrs | 203 hrs | 363 hrs |
| Car Build | £138 | £1,437 | £12,342 |
| Tools / Consumables | £0 | £314 | £459 |
| Total Cost | £138 | £1,751 | £12,801 |