Topic: Want to paint cylinders/head - need some quick info

[capnspif]

kghost, did you also powder coat your cyclinders and head, or would that work against heat transfer? Has anyone had the cases or other parts dipped? It's been a long time since I worked auto parts but I seem to remember engine shops would dip engine blocks to completely strip them inside and out.

I've got my '78 completely torn down now and need it cleaned much better than I've been able to do before reassembly & paint. But I was leaning towards powder coating.

[kghost]

Nah, I chickened out and left the head and cylinders in the rough. Just powdercoated the case's

[Terry in Australia]

Well I took my spare f2 engine apart last weekend to start rebuilding as my "Endurance Racer Project" engine, all the grotty engine components are currently soaking in a big tub of diesel fuel I and took the cases and cylinders over to get chemically stripped. The guy there recommended bead blasting as he said that the "Hot tanking" they do isn't all that sucessfull in removing all the paint and corrosion.

They also do powdercoating there, but he recommended against it, he said that as powdercoat is an excellent insulator it'll keep the heat in (not good) so he'd definately recommend against heads and cylinders, and to a lesser degree, crankcases. Hmmnnn. so what do i do now? Paint comes off when it comes into contact with fuel additives, powdercoat isn't recommended as it keeps the heat in, what do I do?

Tony, the guy who runs the business, is a biker too, and suggested that as my bike is really only going to be a weekend "toy" anyway, to just leave the cases bare? He did his beautiful Kawasaki Z1 900 7 years ago and left the cases bare, and they still look good, so that'll do me. I'll polish the outer covers but the top and bottom cover, cylinder block and head will be "au natural". It'll sure make assembly and fitting back into the frame a snap too.

I saw this in a British bike mag, and all the owner did to combat road salt etc was to spray the whole thing with WD40 once in a while, but as this bike won't be seeing any of those sorts of conditions, it should work fine without it. Cheers, Terry.

[MetalHead550]

LOL!  Or John Deere Yellow!

[Quail "Owner of the comfortable k8"]

I find it hard to believe that a coating of polyester, acrylic, polyurethane, (we call it powder coat) melted onto an engine, would retain heat more than a coating of acrylic, enamel, laquer, polyurethane paint sprayed on an engine.  I know bare metal is the best.  But what could be the reasoning other than "wive's tales" that people have come to belive from fourms such as this.  Every thing is coated and baked in production today.  It may not be applied as a powder but  raw plastic powder or powder mixed with a solvent and sprayed on to a static charged metal part and baked to cure the plastic has to be the same thing.  Engines on new bikes encased in plastic shrouds have to run hotter than these exposed engines we use.

 kghost 
Nah, I chickened out and left the head and cylinders. 

I wish you would check the temp of a painter case and your powdered case and see if I am right. 

[Terry in Australia]

Well Terry, there's coatings and coatings, I guess. Paint sprayed on to engine cases is measured in microns and is a lot thinner than powder coating.

If you've ever had to remove surplus powdercoating from a bearing surface etc, you'll know what I mean, it's an onerous task, that stuff is not only very hard, it's very thick.

Ceramic coating, which is becoming popular lately, is used primarily to retain heat, to insulate exhaust systems in race cars to keep the heat down in the engine bay.

As for the "wives tales", well with respect to the rest of the very knowledgeable contributors on this forum, I reckon I'd certainly listen to the words of my powdercoater, particularly seeing he's losing business by recommending against powdercoating engine parts. Cheers, Terry.

[kghost]

I sort of have to figure.........

The coating is baked on the surface.

The surface as neither increased nor decreased in size or area.

The transmission of heat is based on surface area.

The amount of Radiant heat transer should remain relatively the same.

Black pigmentation increases the absorbance and dispersion of heat.

what the Hell the cases were painted to start with.

[Terry in Australia]

That's right Kasper, in the grand scheme of things, whether or not powdercoating retains engine heat or not should not be of much concern to anyone riding a stock bike, the factory will have built a degree of flexibility into our bikes for various riding conditions and operating temperatures, and for standard engines (such as my F2 or K3) powdercoating is certainly an excellent finish for cases, although I wouldn't consider it for cylinders or cylinder heads.

Re: the factory paint, it was a super thin coat with no primer, and paint, as opposed to plastic coating, "breathes" through it's pores, just like our skin breathes. Plastic coating, being an insulator, does not.   

As the engine that I'm building now will generate a lot more power than a stocker, therefore a lot more heat, I've decided to leave the cases bare, I had to have them blasted rather than "Hot Tanked" so they'll be slightly pitted, which will actually increase their surface area and aid cooling, and with the help of one of my (superb) oil cooler adapters, I'm hoping that it'll stay as reliable as my other bikes. Cheers, Terry.

[kghost]

My point is.............

"Plastic" baked onto the cases will be the same tempurature as the cases.

I will agree that the cylinders and head left bare are probably a good idea. Thats why my are bare. I am not however worried about the other parts.

Oil tempurature will be as good an indication of internal temps as any. It carries away heat. As long as the oil temp (which is really the most critical to engine life) remains within limits, why worry?

I run a 836 in mine. But as you may have noticed there is a cooler. The  cooler is there to combat the high ambient Texas summer temp.

The highest temp I have measured in the tank (where it matters as this is the oil going into the engine) was 93 C. This was after a really hard flog.

Based on experience with aircooled aircraft engines ranging in size from 183 cubic inches to 2800 cubic inches the highest I would tolerate would be about 100 C. While I realize this equates to 220 F (which is the operating range of liquid cooled engines) The oil along with fuel ( remembering the atomization in the carb decreases the air charge temp.) is what adds to cooling.

I haven't experienced any problems with powdercoated cases.

As an aside, what do you plan on doing to prevent corrosion of the cases?

[Terry in Australia]

G'Day Kasper, well I'm not going to do all that much. I've been told that a regular light spray of WD40 will keep the alloy from corroding, but I'm not convinced.

We don't get too much rain around here, not even in winter, and there's no such thing as snow for over 100 miles in any direction, so I don't have to worry about road salt exacerbating the problem.

The bike will live in my garage and will only be used as a weekend toy, so I guess it's not a real problem, but I guess if it looks like the WD40 isn't holding up well, it won't be too hard to pull the engine, degrease it and give it a coat of high temp paint.

Then all I have to worry about is fuel additives lifting the paint like it did on my beautiful F2. Geez, no wonder I drink so much, ha ha! Cheers, Terry.

[kghost]

I too have been toying with the idea of polishing the cases on my next engine. Thought about "engine turning" them too. But, I'll probably clear paint or powder them as
I couldn't bear the thought of repolishing them again