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Thu Feb 25, 2010 9:42 am

I have a new motor, and while its out I have sanded the block to bare aluminium. I know some of the question may be to personal prefance, but I'm thinking about leaving it unpainted.
What would be a way to keep the block shiney, should I spray a clear coat, or do they make a high temp clear coat, or would it be easier to keep it clean by painting it? Right now it almost looks like a polished aluminium motor. I like the look but I haven't seen too many other motors on here like that. Just wondering why most people paint the motor.

Thu Feb 25, 2010 10:55 am

Aluminum by its nature will corrode/discolor in the right elements. You could try to clear coat it. Most polyurathanes will hold up to the heat on the engine case. There is also some nice Chrome or Aluminum paints out there. It's up to you.

Thu Feb 25, 2010 11:11 am

As a general rule, painted metal dissipates less heat than unfinished metal.

This has come up before on here, you might do a search and read them.

One of the most familiar examples of this is with old cast iron hot water or steam radiators found in homes. They are almost all finished somehow, usually many many coats of paint, unless they are behind a decorative cover. Unfinished, they emit the most heat.
'
Paint is an insulation layer and depending upon which paint and even the color the properties are different.

It is said that even the Chrome tin that is so popular on the engine makes it run hotter.

Heat is an engine's enemy, water or air cooled. Water cooled are most often painted for they are iron which rusts badly. With air cooled, Heat is even more a problem. You decide what YOU want to do.

For me, no paint, no clear coat and the original black cooling tin. Too much money invested to risk damaging it by making it "pretty".

Dave

Thu Feb 25, 2010 11:45 am

I'm not sure why they say chrome makes it run hotter than paint, both are a covering. I would assume the only reason they are black from factory, was because of the cost and since its metal it needed rust protection.
But I don't know if they painted the block, I'm thinking they did not from the factory.
I think all the VW's I've owned had the motor tampered with, and they were all painted.

Thu Feb 25, 2010 11:56 am

It has been posted that VW supplied chrome valve covers to make them run hotter in severe cold climates. Believe it when they say chrome runs hotter.

Chrome is not a coating, it's bonded to the metal and is very dense. Paint is much less dense than metal and the lower density lets it act as insulation.

Some paint the block with a VERY thin coat of flat black paint, which in theory runs cooler because (a) it's not a solid coating like more glossy thick paint) and so increases the effective surface area to radiate heat, and (b) the black paint's emissivity is higher than any other color.

I did this once, but the inevitable oil and gas leaks made it look crappy fast, so next time it was out I stripped it to bare metal.

The flat look of a stock block is a coating of aluminum oxide which inhibits further corrosion, Polishing means you remove this and are now on a treadmill of continual repolishing to keep it looking nice.

Fri Feb 26, 2010 2:51 am

So do they sell the aluminiom oxide so you can re-coat it back? I only cleaned the part that will be seen with all the tin on, I would say about 70% of the block isn't seen.

Fri Feb 26, 2010 5:35 am

BUGTHUG wrote: So do they sell the aluminiom oxide so you can re-coat it back? I only cleaned the part that will be seen with all the tin on, I would say about 70% of the block isn't seen.

Goggle is your friend!
I stumbled upon this article
http://www.pfonline.com/articles/090203.html

It seems like an involved process but this paragraph struck me as interesting for it describes what appears to be an original VW Case finish look!

"The third step involves treatment in a proprietary potassium permanganate solution at 130-140F for at least 3 min to create a manganese oxide-aluminum oxide coating of about 30-40 nm thick with a very well defined structure (see Figure 3). The metal itself will have a clear to light gold, iridescent finish. The coating is quite hard and scratch resistant, will withstand temperatures up to the melting point of the aluminum and will not degrade over time. "

Is this what VW did ? I haven't a clue. Just found it interesting for recreating the original look is frequently discussed here.

Dave

Fri Feb 26, 2010 8:10 am

Aluminum oxidizes naturally over time. I don't think VW did anything special to the cases other than clean them after machining.

Fri Feb 26, 2010 8:29 am

KTPhil wrote: Aluminum oxidizes naturally over time. I don't think VW did anything special to the cases other than clean them after machining.

Yes, it does oxidize but it doesn't naturally create that clearish amber color so prevalent of old VW cases.
(clearish, I made that one up! Spell check doesn't like it! :lol: )

Fri Feb 26, 2010 8:35 am

The amber color might just be left over cosmoline from storage, not frmo a surface treatment of the metal.

Fri Feb 26, 2010 9:17 am

KTPhil wrote: Aluminum oxidizes naturally over time. I don't think VW did anything special to the cases other than clean them after machining.

Is the OP's case an aftermarket aluminum or a Type IV?
If not then an OEM Type I or Type III would have been made up of primarily magnesium. Corrodes even quicker than aluminum.
The OEM new universal case on my engine is garaged and not usually getting wet and it looks like this after 4 years (3500 or so miles?). I have never attempted to clean it.

Fri Feb 26, 2010 10:33 am

Mayhem, thats what my new Brazilian case looked like. But you can tell there really isn't that much case seen when its dressed out in the tin. Maybe a little scotch brite might not be too hard to keep it nice looking .
I do have the motor in the buggey painted a silver grey look, and it cleans up pretty easy, but most of it is exposed to view.
How hot does the block get? not much over 300 degrees? maybe a good clear coat would withstand that heat? OK thanks youall

Fri Feb 26, 2010 11:06 am

OEM cases are magnesium. My new mexico and brazil cases had a gold finish to them and did not oxidize for many years. When it was time to rebuild the mexico case I scrubbed it down with steel wool and what was left of the coating was removed. A month or so later a light haze of white chalky oxidation was seen. Although the cases are not coated as much as they were back in the 50s/60s the gold protective coating DID keep them from oxidizing.

Here is a link to have your case coated as it was from the factory.

http://www.thesamba.com/vw/classifieds/detail.php?id=587241

Here is the thread discussing the gold coating

http://www.thesamba.com/vw/forum/viewtopic.php?t=142438

Fri Feb 26, 2010 12:23 pm

derluftwagen wrote: OEM cases are magnesium. My new mexico and brazil cases had a gold finish to them and did not oxidize for many years. When it was time to rebuild the mexico case I scrubbed it down with steel wool and what was left of the coating was removed. A month or so later a light haze of white chalky oxidation was seen. Although the cases are not coated as much as they were back in the 50s/60s the gold protective coating DID keep them from oxidizing.

Here is a link to have your case coated as it was from the factory.

http://www.thesamba.com/vw/classifieds/detail.php?id=587241

Here is the thread discussing the gold coating

http://www.thesamba.com/vw/forum/viewtopic.php?t=142438

Interesting reads. Still no agreement on what was on the cases from the factory though. There is a strong argument made that they were indeed coated with something.
All of the discussion centers on the US examples. I wonder if the Home Market had the coatings or if they were for the ocean voyage?

I also know that the castings will disintegrate over time. I don't know the why of it but I had a 57 case sitting in the garage that ended up as a solid top with a white powdery nothing on the bottom. "Rotted" completely away until the cam lifters were hanging out.
Some sort of protection seems prudent but what?

Dave

Fri Feb 26, 2010 1:37 pm

I like mine painted.

Fri Feb 26, 2010 3:59 pm

I always liked bare metal, which made any oil leaks easy to trace. When it gets too grungy, I'd go down to the car wash with soap and hot water, hitting the underside, tranny, and front axle while I was at it. Painted blocks don't show leaks as well.

Fri Feb 26, 2010 4:33 pm

ConcreteAce, man thats black, black baby. Looks nice.
Djkeev, I wonder if the differnt metals inside your block made it have a chemical break down? Like a battery when you use differnt metals for the cable bolts, and cooper it turns white powder.

Sat Feb 27, 2010 6:13 am

BUGTHUG wrote:
Djkeev, I wonder if the differnt metals inside your block made it have a chemical break down? Like a battery when you use differnt metals for the cable bolts, and cooper it turns white powder.

I sent Nick from NSRacing an email asking why he thought the case would dissolve. He seems very knowledgeable about these engines. His reply was an acid was introduced to corrode it and once started keeps going and can be difficult to stop.

I then Googled acid corrosion of Magnesium and found several threads on the effects Hydrochloric acid have. My thoughts are that a battery was probably knocked over and the case ended up sitting in a puddle of acid for a long while. I have an old case that is trash, thinking up picking up a bag of acid and seeing what the long term effects actually are on a case.

Yes, I know the dangers of the acid, thanks, I'll be careful. I have an outbuilding I can just set it in for a few weeks and see what happens.
I also have seen the videos of what happens with the introduction of the metal into the acid, goggles and gloves a must!! I'll probably dilute it down as if it were a spill on a moist concrete floor.

Dave

Sat Feb 27, 2010 7:41 am

I have always tried to find a nice finish natural case for pretty engines and the nasty cases just end up as regular engines for transportation. To find a naturally nice finish case , you may have to inspect quite a few. I like a natural gold'ish tone for a mag case and a smooth no flaws appearance for aluminum cases.
I have always heard that when you pollish aluminum that the heat gets trapped and cant escape through the solid pollished surface.

Sat Feb 27, 2010 3:02 pm

I wonder by grinding down the rough casting's, if it might make the case stronger, or maybe weakens the metal?
Vaughn bros, thats a nice lookin motor.