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Simoniz VHT Paint

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Murf:
Google says air cooled motorbike engines typically run at 100 deg C to 180 deg C  with 200deg C + being too hot 🥵
I would worry about aluminium cylinder heads becoming warped if heated to 200C when not bolted down and cylinder liners getting lose in their bores and moving a bit.

Theoldboycarter:
Thanks everyone for your replies. Nurse Julie, when you say do exactly as it says on the tin, do you mean including heating to 220 degrees c? As Oddjob mentioned, I've seen on the internet that aluminium can distort at relatively low temperatures, but then I am aware you can't believe everything you read on the net.

Oddjob:
I was watching a How it's Made TV program the other night and oddly they referenced alloy distortion in it, it was 150c so that's confirmed. There was also a program on the SR71 Blackbird plane, it also mentioned that they couldn't make it out of alloy like the U2 again mentioning the distortion problem above 150c. They made it out of titanium instead.

Nurse Julie:

--- Quote from: Theoldboycarter on February 26, 2026, 10:54:07 AM ---Thanks everyone for your replies. Nurse Julie, when you say do exactly as it says on the tin, do you mean including heating to 220 degrees c? As Oddjob mentioned, I've seen on the internet that aluminium can distort at relatively low temperatures, but then I am aware you can't believe everything you read on the net.

--- End quote ---
Alloy sheet may distort at 150° but alloy engine cases don't.
The only time we prepare to prevent distortion, is on bottom engine cases that need major TIG welding for major chain  damage repairs on Sandcasts/ K0's, which is 660°. We bolt the case to a jig to prevent distortion during welding.
As far as the painting is concerned, the most important thing is to make sure all old paint/ oil etc is removed prior to painting. The parts must be thoroughly clean, we had all our engine chemically dipped to ensure no contaminates were left on or in the metal. If there is any left, it will just leach out under the new paint. Wipe parts down with clutch and brake cleaner.
So......
1. Prep the cases fully.
2. Heat cases in oven to 50°c.
3. Heat can of paint in hot water.
4. Spray 1 mist coat.
5. Leave for 10 mins and spray another light coat.
6. Repeat No.5.
7. Air cure somewhere warm and dry for up to 24 hours.
8. Put oven on at 50° and and gradually increase in 50° increments over 1½ to a maximum of 220°c.
9. Turn oven off, leave parts in oven to cool until cool enough to handle.
10. Remove parts from oven and air cure for 24 hours somewhere warm and dry.
Doing it this way, we have never had any distortion ( the parts are only at 220° for about 10 minutes), nor have we had any discolouration.
As far as fuel damage is concerned, paints like this are 'fuel resistant'. If painted and cured correctly, wipe any fuel spillage off, ie at the petrol pump, as soon as you can and it will cause no damage. Leave the fuel on without wiping it off, it would cause some damage. The easiest thing to do is not have leaky carbs or tap, then you won't have a problem.

taysidedragon:

--- Quote from: Oddjob on February 26, 2026, 02:36:20 PM ---I was watching a How it's Made TV program the other night and oddly they referenced alloy distortion in it, it was 150c so that's confirmed. There was also a program on the SR71 Blackbird plane, it also mentioned that they couldn't make it out of alloy like the U2 again mentioning the distortion problem above 150c. They made it out of titanium instead.

--- End quote ---

At Mach 3 the airframe got very hot and titanium had to be used to withstand the high temperatures.  Nearly every photo of the Blackbird in the hangar will have large drip trays under the aircraft because it used to leak fuel badly on the ground, possibly because of the expansion and contraction.

Concorde only flew at Mach 2 and used to expand about 12 inches in length at that speed.

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