As part of my engine rebuild I want to paint the crankcases. I want to use VHT paint as I believe it should stand a better chance of staying on a hot engine, my understanding is the paint dries but only cures fully when heated up i.e. by running the engine, however I want to paint the split cases and then re-assemble & rebuild the engine which will take some time and require some handling so I'm thinking of 'curing' the paint in the oven to avoid the finish getting too badly scratched during this time. Anyone got any tips on temperature/time etc?
IIRC it says on the tin... 160 degrees rings a bell. Can't check til I get home tonight. I did this chap Heads 8 - Done by Lindsay fae Angus, on Flickr in VHT and baked in the oven (when it was bare - obvs :smile. Am very happy with the finish.
Planning on using Halfords VHT ('coz I've got some) but it doesn't give any directions and I'm finding conflicting info on the 'net from not neccessary at all to cook at 350c. I was thinking of a bake at 80ish and then maybe 120ish? I don't want to go too hot because I was hoping not to melt the swingarm beaings (or anything else for that matter)...
That's what I was thinking but some are saying you need 200c to cure and I don't want to go that far. Plus, as you say it won't (hopefully) run that hot anyway.
Actually the 'not neccessary', '200c' and '300c' are all from Halfords 'technical' staff's Q&A inked from the product...
I don't know what the Halfords product is like, but I can tell you that the two I mentioned above won't cure enough on the engine casings if you are relying on a running engine heat alone......It might be enough for the heads and barrels. There are two ways to cure the casings.......Blowlamp from the inside (not easily controlled heat) or the oven........Whack the oven up to nearly max (say 150+) for two hours and open the windows. The above two paints aren't entirely solvent resistant although Sperex is much better than Hycote (I suspect the Halfords product is much the same stuff)......Also Sperex resists abrasion much better and will to some extent polish with a dry rag from matt / powdery to an almost satin finish. I had the same handling problem with my zorst headers.....they were bound to get scratched as I tried to assemble them, so it was stick them on an iron bar clamped in the vice and blowlamped up the inside....still got scratched a bit though; however the Sperex paint will touch up OK whereas Hycote won't. AL
I reckon blowlamp is too hit & miss. I Can just fit a crankcase 1/2 in the oven, Presumably the swingarm bearings will be OK at 150?
Well the grease will melt......which might mess things up a bit......but I doubt if the bearings will be damaged (let the whole lot cool down naturally) however, aren't there seals present? Don't know how they will react..... Maybe you could get away with 90mins at 150+ in the oven......BTW, put the casing in the oven while cold, then switch on.......let the heat build up rather than putting it into a hot oven..... It will smoke, so whip the batteries out of the alarms...... AL
The Halfords silver VHT paint is great! Good finish etc but NOT petrol or oil proof, its designed for exhausts... as I found out lol Would recommend a petrol-proof laquer over the top? What temp would a standard two-pack paint endure?
When I first used Sperex it was completely unharmed by any solvents once it had cured.....my Guzzi downpipes did thousands of miles without any problems......I guess now that Simoniz have taken on the Sperex product, it's probably High Melting Point coloured Turtle Wax.... AL
OK so I baked them at 80c for 1 hour, let cool and then 160c for 2 hours, the powder-on-your-fingers thing seems to have stopped so hopefully it'll be good. Could just fit each side in the oven on the diagonal;
sorry to dredge up and old thread but how well have your painted cases held up dukedesmo? did you use a petrol resistant laquer? how is the colour match for the OEM engine grey?
Paint has held up fine, I didn't use any lacquer. Not sure if the colour match is perfect? but as I painted the whole thing it doesn't matter to me. But I painted the crankcase side covers with a 'normal' black paint (albeit using etch primer first) because I didn't want the matte look of the VHT and although it hasn't come off, it does get a bit soft when the engine's hot - so VHT is definitely the way to go. Eventually I'll repaint the covers but they still look OK for now so as long as I don't use any cleaning products on them when they're hot it's good.
I use Plastikote Industrial Heat Shield Black on the RD as the engine is all satin black. You don't use primer and gives a lovely finish after curing. You don't use primer under HT finishes, very few primers are HT and it must actually say it is HT otherwise it will melt and just "float" under your final finish. High temperature paint MUST be properly cured or it won't work and the curing process has to be hotter then the surface it is being applied to. Therefore, you cannot cure engine casings by the engine heat alone. After many experiments I have found the best method for curing is as follows..... the method is as important as the temperature and is not stated by manufacturers in most cases. Apply in 3-4 coats without overloading, flashing off each coat with a heat gun set to about half heat. Allow to air-dry for an hour somewhere warm (more than 18C) for the solvent to fully flash off. You must cure the finish on the same day you paint. Pre-heat an oven to 150C and place your parts in it for 15-20 minutes and turn off the heat. Leave to cool in the oven for an hour with the door closed. Think of an unbelievably good explanation for the missus as to why the oven and kitchen is stinking of paint. The curing process also improves the finish AND makes it petrol proof.............. If you have any god-awful bits of casting (RD barrels are appalling unless you tidy them up), grind using a flap wheel or Dremel them smooth, filling any holes with Chemical Metal. Now, the above method is for the stated paint type, but I have used it for others and it works. As it only comes in black this is of no use to most Ducatis but Plastikote do other "Hot" paint that comes in black, aluminum, white and blue. For these they state that you must cure at 316C for 45 minutes. I don't advise using lacquer on the really hot bits like the heads and barrels as eventually it will "craze". For my outer casing restoration I used Chrysler Titanium (code PDT) to get the dark metallic grey as found on the 916, with acid etch primer underneath and 2 light coats of Halfords Petrol Resistant Lacquer over the final colour, deliberately sprayed on "dry" to give the desired finish. Halfords will mix you up the colour in a spray can but it's not cheap at £15 a pop and you will only just get one set done as it comes out of it like a fire extinguisher.............. You do not oven cure this finish.
