TheSamba.com :: View topic - Heater box paint color

Thu Mar 18, 2010 11:00 pm

I am in the middle of aquiring all of the various engine tin pieces that my astute PO decided weren't needed. I am getting them ready to paint (satin black of course). I know the tin needs to be black for cooling purposes, but how about the heater boxes? Mine are the grey factory color. Would it change anything if they were painted the same color as the tinware? Would you need a high temp paint if only the tin part of the boxes was painted and not the exhaust portions on the ends? Does it even matter the heater boxes color?

Thu Mar 18, 2010 11:01 pm

Paint it any color you want. I used high heat paint myself on the tin portion and exhaust portion of the heater boxes on my car only because it was the only paint on hand and I figured it wouldn't hurt.

Fri Mar 19, 2010 1:25 am

any color you want,, BBQ paint works the best, but any high temp paint works.. you don't wont to paint the case, but on the tins color don't madder as much as you think.. I have A completely chromed out motor on my daily driver and I have never over heated it,, And I mean Completely chromed out..

Fri Mar 19, 2010 6:09 am

Reality is that you don't really need to use high temp paint on any of the tin. Even the cylinder tins don't get hot enough to make a difference.
I've seen engines with rattlecan gloss enamel that don't have any issues.
I used high temp paint because I thought I had to, but it's flat, not gloss, and I really don't like the look. I painted my heater boxes grey, but purely for visual reasons.

Sat Mar 20, 2010 12:37 am

Let me re do that, I meant to post that as too thots,,

On the heater boxes any color you want,, BBQ paint works the best, but any high temp paint works...

On the tins it really don't mater what you use....

Sat Mar 20, 2010 2:14 am

as stated tinware doesnt get hot enough to call for engine enamel
and quite often those engine enamels need to get to a set temp to harden properly

in my younger days ive painted up tinware just using $2 rattle cans and its lasted well for years
its all in the prep and application

painting the block never ends well though

Sat Mar 20, 2010 3:14 am

although the theory is sound.. I don't believe it would make a big difference to paint your tin white vs black or chrome. For several reasons. Firstly and mostly.. they aren't heat sinks to begin with.

They duct the air. The air is doing the cooling not the tins.

They're in direct contact with the engine and conductive..(and insulate given a no air movement scenario, no matter how much heat they can absorb)

Even if painting increased substantially the radiant heat absorbed by the tin.. To what end? So now you have hot tin (which of course isn't there to be a cooling mechanism in the first place). Radiating, convecting and conducting heat into the engine compartment. Like from where your intake air comes.

The hot air is not just radiating heat.. its conductive and convective meaning that the color means nothing what-so-ever to the heat exchange at that pint. It just falls back on the laws of heat exchange.. having to do with the difference between the two mediums.
I've not been to physics class in 20+ years.. and I don't think we er' talked about that type of thing really beyond definition.

I'm not trying to say it hurts anything at all to paint it black... Of course... but it seems to be a 6 of one 1/2 dozen t'other scenario.

Sun Mar 21, 2010 3:40 pm

Good info. So, it looks like painting the tins is only for rust prevention. One other question somewhat relevant to topic. Say the engine has all the rubber seals for the tinware & all of the tinware is present and accounted for. Has anyone sealed the tins together with something to improve the negative pressure inside the engine compartment (IDK like silicone or homemade gaskets)? Would that improve the engines ability to cool enough to make it worth the effort?

Sun Mar 21, 2010 5:06 pm

My thought is that the VW engineers kinda understood what they were doing and would have sealed the tins more tightly if needed.

Sun Mar 21, 2010 5:32 pm

Yea.. I keep wanting to eliminate gaps and such.. then I realize.. its a "stone age" engine.. gaps don't mean squat.

For "german engineering" its not terribly impressive. Maybe it is by 1938 standards.

Sun Mar 21, 2010 6:32 pm

Guess that's my obsessive/compulsive, ADDHD side coming out :lol: Considering that many folks don't even have all their engine tin anyway, and think it's not even needed.

Sun Mar 21, 2010 8:30 pm

Beetle tin was painted black by VW because it was inexpensive and would contrast nicely with any body colour. When your decklid is closed there is no visible light reflection/absorption, so in the shade there really is no colour to affect temps...which it wouldn't for cooling tin anyway, since the purpose of tin is to direct the air, as pointed out above.

It's possible that exposed valve covers (eg. baja bug) might affect temps somewhat...

Sun Mar 21, 2010 11:20 pm

I'm just trying to get people thinkin about it.
I keep getting people telling me I should paint this or that.. or that they did.. to make their engine more powerful.

"my Ls2 should be putting out 475hp now"..
Did you get it dyno'd?

"no, it came at 400 and i put on the CAI and cat back and painted my exhaust and intake and oil gallery".

Comes back from dyno at 325.. completely confused because he's falling prey to the same type of folk that own GNC and Mens Health magazine.

Sun Mar 21, 2010 11:57 pm

Buggin_74 wrote: as stated tinware doesnt get hot enough to call for engine enamel
and quite often those engine enamels need to get to a set temp to harden properly

in my younger days ive painted up tinware just using $2 rattle cans and its lasted well for years
its all in the prep and application

painting the block never ends well though heater boxes aren't part of the tinware thy are part of the exhaust and do git hot.. after A long drive I would put my hand on the fan shroud, but I share as hell wouldn't touch the heater box..

Tue Mar 23, 2010 12:22 am

vw_hank wrote: heater boxes aren't part of the tinware thy are part of the exhaust and do git hot.. after A long drive I would put my hand on the fan shroud, but I share as hell wouldn't touch the heater box.. :lol:

Tue Mar 23, 2010 7:54 am

Here's my take. The reason VW pained all of the engine tin black was because black help dissipate heat. I want the opposite for the heater boxes, because I live in cold Colorado. So I painted mine silver (to hold heat). Chrome would do the same. Use high temp paint. I used 1200 degree rattle can pain from Autozone. Make sure you do the prep correctly. Otherwise pain will flake off. Also adhere to the curing cycle specified on the can. It smells bad for the first 100 miles.

Tue Mar 23, 2010 5:33 pm

Yehan73 wrote: Here's my take. The reason VW pained all of the engine tin black was because black help dissipate heat.

As already stated in this thread, that assumption is incorrect. The tin was painted black to contrast with all body colours.

Chrome might help retain heat within the valve covers (but not the shroud or cylinder tin), as the valve covers fill with oil during operation. The tin just directs air...

Tue Mar 23, 2010 6:27 pm

Yehan73 wrote: Here's my take. The reason VW pained all of the engine tin black was because black help dissipate heat. .

the tinware's "job" is not to absorb and dissipate heat, but to direct air to where it needs to go... if it were intended to dissipate heat it'd be finned...

glad to see guys on here still willing to say this, I've gotten so much crap over the years for telling that the tinware isn't "cooling" the engine that I've nearly given up... Parrots pecking at you for years will wear ya down.. :lol:

Wed Mar 24, 2010 7:15 am

Quote:
As already stated in this thread, that assumption is incorrect. The tin was painted black to contrast with all body colors.

and where did you get this information from??? All the engine building books I've read states the importance of color (even gloss vs matt) Was there a VW publication that say "We painted it because it was a cheap color".
There's a video on youtube, that show the engine temperature of a chromed out bug and a black painted bug (not sure if it's still there). There was definitely a difference in the surface temperature.

Wed Mar 24, 2010 7:35 pm

Okay, first of all, some of this is repeated from above:

1. When the deck lid is closed, the engine is in the "shade", so no coloured light is being absorbed or reflected, therefore, there is, in effect, no colour. Paint it green or blue or red or white and it doesn't matter. That's why so many custom Beetles have painted shrouds and run just fine for years. Now if you have an open engine bay, like a baja bug, THEN you might get some heating of the tin as it would be exposed to sunlight.

2. Several ACVW variations had brown, green, yellow or camouflage paint (WWII) on the shroud and tin...in the heat of North Africa, no less, and they were noted for their durability, when other vehicles over-heated.

3. I've had coloured shroud/tin in the past, including red and orange set-ups (hey, it was the '80's :wink: ) and the temp gauges never read any differently. Those engines racked up a pile of mileage, too.

4. Regarding the video, what specific parts were chromed? If so, do we know if it was actually the "chrome" causing the problem, or the crappy aftermarket shroud design. At one time, you could get quality OEM-style chrome shrouds and they worked just fine...now you have Made in China crap.

The above comments only refer to the fan shroud and cylinder tins, as valve covers are a different matter...