Cylinder and engine paint questions.

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

12notes

Well-Known Member
Lifetime Supporter
Log Member
Joined
Aug 27, 2014
Messages
958
Location
Louisville, KY
I'm stripping the 2-3 layers of paint (orange, silver, and red) off the Global 1/2 VW I'm close to assembling for the Hummelbird I'm building, and wondering what needs paint and what doesn't. The cylinders are steel, so I know I need to paint them. Cylinder heads and valve covers are aluminum, the whole engine weighed 85 lbs, not sure if the block is aluminum or magnesium. Do any of those need to be painted, and is there a recommended paint? I seem to recall Pops stating the valve covers should be painted black to help with heat dissipation, I assume black paint on the cylinders would be good too? I have a can of VHT black engine enamel which is rated for 550 degrees, is that good enough? Should I use primer, or will the paint be fine as is?

I'm not building a show plane, so basic protection is good enough for me.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
12,222
Location
Memphis, TN
I would go black with everything. How thick is up to you. Black is better for heat dissipation. How much better is...
 

Pops

Well-Known Member
Log Member
Joined
Jan 1, 2013
Messages
7,658
Location
USA.
Bob Hoover says to use a light coat of enamel and thin with gasoline for a flat finish for the case.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
7,368
Location
North Carolina
I used to use a cheap brushable product called 'pot black' in the UK for motorcycle cylinders. I could feel increased radiation after painting an aluminium cylinder. It was thin stuff with plentiful solvents. Thick paint will reduce heat transfer, though not a huge amount. I used to go as thin as would be uniformly black. Worked fine for me, didn't seem to be prone to rust on the few steel bits I painted. I never primed. Just make sure the surfaces are good and clean. Bead or sand blasting to get oxidation and old paint off is a good idea if you can.

Pretty much any colour paint will increase heat radiation. Heat is radiated at a wavelength where just about all paints are quite 'black', even visibly white paint. So, feel free to go psychedelic! Some metallics break that rule.
 

12notes

Well-Known Member
Lifetime Supporter
Log Member
Joined
Aug 27, 2014
Messages
958
Location
Louisville, KY
Thanks everyone. I'll paint everything with rattle cans of VHT black engine enamel, once I get the rest of the paint off. I've already used 3 spray cans of Aircraft Remover, had to order more to get the small amount left on the cylinders and heads.
 

karmarepair

Well-Known Member
Joined
Jan 13, 2011
Messages
74
Location
United States
The VHT high temperature paints have a lot of metal salts in them, and actually hold heat in. Thinned regular enamel is better for heat dissipation.

Paint the case, paint the barrels, leave the heads bare, IMHO.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
7,368
Location
North Carolina
I've also used stuff for wood stoves.
You might be able to test emmisivity with a laser thermometer. Paint one piece of metal with several test paints, get it hot, and see which paint registers highest with a laser thermometor. That is the paint with the highest emmisivity and the one you want. Soot is very close to 1 and your benchmark. Most paints are pretty high at cylinder head temps.
 

12notes

Well-Known Member
Lifetime Supporter
Log Member
Joined
Aug 27, 2014
Messages
958
Location
Louisville, KY
The VHT high temperature paints have a lot of metal salts in them, and actually hold heat in. Thinned regular enamel is better for heat dissipation.

Paint the case, paint the barrels, leave the heads bare, IMHO.
A bit late now, engine is already painted.
 
Group Builder
Top