Spitfire Engine & Chassis

The past few weeks have all been about getting the engine stripped down and painted. I’ve also stripped the chassis down, applied a couple of coats of Por15 and a couple of coats of self-etch primer specifically designed to etch the Por15 and provide a suitable surface for the top coat. I think the chassis could do with another coat or two of etch primer. It’s not high build primer and won’t really need sanding so three or four coats shouldn’t build up too thick. I think getting coverage on all the intricate parts of the chassis will be difficult but I’ll just have to touch up those bits afterwards. I’m planning on coating the inside of the chassis with some Dinitrol cavity wax.

After stripping the engine right down and removing the core plugs I gave it a really thorough clean inside and out. Jet washed all the water and oil channels and thoroughly dried it with compressed air. I then replaced the core plugs, degreased it and sprayed it down with Por15 Metal Prep. It needs rinsing off after twenty minutes or so. It removes rust and leaves a zinc coating on the surface after you’ve dried it off. I replaced some of the oil gallery bolts then masked all the surfaces that would need leaving bare. Basically anywhere that is a mating surface of some kind. In order to get nice clean edges with the masking tape, tap a hammer lightly along the edges to break the masking tape (apparently an old gasket making trick). Works really well.

Next step is a very thinned down coat of Por15 as an undercoat. Por15 has very high temperature rating and remains flexible. Hopefully that means it will expand and contract as the engine heats and cools rather than cracking and flaking off. Once that’s slightly tacky, after about two hours, a coat of Por15 Engine Enamel. It turned out pretty well but I should have thinned the engine enamel down a bit more as it was a warm day and it was drying up while I was painting it on. Any exposed bits that I come across while I’m re-assembling it I can touch up. The result is this which I’m pretty pleased with though.

After measuring up the bore diameters with an internal micrometer we decided that it didn’t need re-boring although the pistons are a bit scored and will need to be replaced. With a new set of pistons and rings the cylinders needed deglazing which is done with a tool such as this:

With some fork oil rubbed in to the spring loaded stones and plenty inside the bore the tool fits in to a drill and you slide it up and down the bores fairly rapidly. The reason I didn’t go too slowly is to try and get a cross hatch pattern which helps piston ring seating. Apparently too much horizontal pattern can cause premature ring failure. It took a little while longer than I thought it would. Just goes to show how hard the cast iron is that the block is made from. There’s a few light score marks and a tiny lip in places from the pistons but I think it’ll be OK.

Next steps will probably be stripping down the drive shaft and brake assembly that I’ve not done yet (hopefully without wrecking a drive shaft this time!). Get a coat of Por15 on that then next month I should be in a position to for the final stages of paint on the chassis.