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Discussion Starter #1
I've done a complete engine strip down. My factory clearcoat was crackling and yellow on many parts, so I've stripped it off with paint stripper and now I've been polishing all the parts.

Not being a huge fan of polishing my intention is to clearcoat all the shiny polished parts (they are not a mirror finish for adhesion) and I intend to spray paint the cylinders in a black matt all of this in high temp engine paint/lacquer to give the engine a nicer and longer lasting appearance.

So all my parts other than my cylinders have been polished and ready for as thin a coat of lacquer to be sprayed on as possible.

Now before I do my one concern is about heat retention, firstly apparently highly polished parts are not good at giving off heat and then there is a lacquer coat on them. Also the cylinders I intend to paint matt black will have an additional layer albeit very thin layer of extra material to release heat.

Is a thin coat of paint/lacquer negligible? I have heard of people powder coating their engines which to me just sounds silly as the powder coat is thick (and then they have engine failures).

Here is my intention for the engine:

 

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Re: Opinions on clearcoat, engine painting and heat retentio

Most of the heat goes out from the heads, and most of the oil cooling is through the finned crankcase bottom. The polished side covers don't need to shed much heat, and painting the cylinders shouldn't make it run much hotter, either. Gloss or rough, most heat is conducted to the air, and a smooth surface isn't compromised that much for heat conduction, as long as air flow is good.
 

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Discussion Starter #3
Re: Opinions on clearcoat, engine painting and heat retentio

Most of the heat goes out from the heads, and most of the oil cooling is through the finned crankcase bottom. The polished side covers don't need to shed much heat, and painting the cylinders shouldn't make it run much hotter, either. Gloss or rough, most heat is conducted to the air, and a smooth surface isn't compromised that much for heat conduction, as long as air flow is good.
Well I was going to clear coat the whole bike including the head crankcases etc. (Other than the black cylinders of course) So I should be ok then?
 

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Re: Opinions on clearcoat, engine painting and heat retentio

I have yet to find a clear coat that does not peal off within a year or two when applied to the engine, even the original Honda clear coat did, and cleaning up half pealed paint from tight spots on a engine is not fun. If you must --- coat the covers but don't do the head and cylinders.
If any one knows of a clear coat that really does stay on long term on an engine that gets regular use, we would all be interested.
 

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Re: Opinions on clearcoat, engine painting and heat retentio

450roo said:
I have yet to find a clear coat that does not peal off within a year or two when applied to the engine
Especially the heads, because they go from cold to really, really hot; paint doesn't like that, much, and, since it's aluminum, it expands a lot, stretching the paint until it breaks. The side covers don't get very hot, so the clear I got from Eastwood for bare metal is holding up pretty well.
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Hi,

Whatever coat you use, make sure the head is very clean. In most cases these heads are porous (casted aluminum with high amounts of zinc and silicon).
Grease, water and dirt are trapped in the pores, and hard to remove. Chemical cleaning will get the pores clean and let the paint hold longer.

Not being original, but better in many ways is to vapor blast / wet blast the cylinder and head, and not paint / coat them at all. I also experimented with a zinc layer and anodizing the head.

For years I tried to restore the original surface finish of the CB72/77 heads. In 2005 I got a NOS head, boxed and in plastic. The surface finish was a zinc layer. This zinc layer is formed during the casting process. The picture shows the original finish, being zinc. This zinc will vanish during the years and the cylinder and head turns dull. It's difficult to restore the zinc layer.

[attachment=0:2yhzhgrf]nos head plus nos bolt.JPG[/attachment:2yhzhgrf]

btw: what I do to make the cooling more efficient is enlarging the openings of the air channels between the cylinders and the air channels in the head itself. When you take a look you will notice that in most cases these openings are closed for 30% or more due to the moulding process. I also found cylinders with closed air channels (a very thin layer of aluminium (fleese) closes the opening

It takes me two to three hours to do that with a Dremmel, it improves the transfer from head (and cylinder) to air massively. Also make sure that the air can flow freely away behind the cylinder and head.

Making sure that the mixture is a little on the rich side is also improving the cooling of the head and cylinder.

Jensen
 

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Discussion Starter #7
Re: Opinions on clearcoat, engine painting and heat retentio

450roo said:
I have yet to find a clear coat that does not peal off within a year or two when applied to the engine, even the original Honda clear coat did, and cleaning up half pealed paint from tight spots on a engine is not fun. If you must --- coat the covers but don't do the head and cylinders.
If any one knows of a clear coat that really does stay on long term on an engine that gets regular use, we would all be interested.
I find the original Honda clearcoat to hold up quite well on the old bikes, I've seen them good for 10 years for example. If I could clearcoat like that it would be ideal.



This is the stuff I've bought and was recommended to me apparently good up to 288 degs C but I'm no authority on the subject.

http://www.cbxclub.com/davespage/mcy84-1.html

And this is the site I've been reading as well as others.

Not being original, but better in many ways is to vapor blast / wet blast the cylinder and head, and not paint / coat them at all. I also experimented with a zinc layer and anodizing the head.

For years I tried to restore the original surface finish of the CB72/77 heads. In 2005 I got a NOS head, boxed and in plastic. The surface finish was a zinc layer. This zinc layer is formed during the casting process. The picture shows the original finish, being zinc. This zinc will vanish during the years and the cylinder and head turns dull. It's difficult to restore the zinc layer.
Thanks Jensen, this is fascinating to me as I had investigated anodising early on although apparently the avenue is closed to the Hondas we have as there is such a high silicon content in the alloy, meaning the finish is terrible (someone please verify I have no idea if this is really true!).

Whats more I am zinc plating at home, its a relatively easy process bolts, kick-starters etc. the zinc can be polished up (not to mirror finish but a nice lustre) and lasts several years, the only troubles I'd have with zinc plating a head and engine parts are, is my power source large enough? And do I have a big enough container for the electrolyte and head to fit? (and I can find no professional zinc platers anywhere!!).

I can also fill in pitted chrome by sanding it and then plating with zinc (the zinc won't stick to good chrome) and then polishing up, its not perfect but secures and touches it up, it often makes the pitting damage unnoticeable and gives a few more years out of it.

Anyway so I'm still a little stuck between deciding what to do, one side of me says clear coat and see what happens I can have the engine out again in a years time to deal with it if it messes up, the other side of me says leave it all as it is and now the zinc plating idea has come in as well!! (It must be noted though that I have no interest in an OEM finish!)
 

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Re: Opinions on clearcoat, engine painting and heat retentio

I have been using Eastwoods Diamond Clear for close to a decade now and it's holding up very well.

I have some motors with 20,000 miles on them since clearing and it looks as good as the day I sprayed them...no yellowing or pealing.

it also is very easy to keep your motor clean with this stuff. just wipe off all the road grime with soap and water.

they make an aerosol spray can version of this paint...DO NOT USE. get the stuff in the little cans that you apply with a spray gun.
Like anything prep is the key to a lasting finish.

I beadblast my motors,
then wash with dish soap,
then with a 10% bleach solution and water.
Air hose them dry
one final Acetone wipe just before spraying.
give them 3 thin coats.

I leave the cases, ,cylinders and heads beadblasted and polish the side covers.

it sticks and wears great.
search for my builds on this site for pictures of my engines

And by the way, if your motor is properly tuned (carbs, timing, valves) then the minor differences in cooling with different head treatments are negligible.

I have head temperature sensors on each cylinder of my built CB350 motor (with the above clear coat treatment) in my cafe bike running 67mm 10.5 to 1 compression with a megacycle cam and the head gets up to about 290 F at idle in traffic and runs at 238 F on the move.
 

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Discussion Starter #9
Re: Opinions on clearcoat, engine painting and heat retentio

I wrote to Eastwoods regarding the differences between their Diamond Gloss and Satin on an aluminium engine. This is the reply I got:

Hello

The Diamond Clear is not designed for an engine, it gets too hot. We do have a high temp VHT Clear good to up to 550 degrees item 13845Z.
And this is exactly the VHT clear spray can I already have.
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Try it on something other than your engine first, I have found that some VHT paint will wash off with fuel, even after drying for a long time.
Hope it works!
 

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Discussion Starter #11
Re: Opinions on clearcoat, engine painting and heat retentio

450roo said:
Try it on something other than your engine first, I have found that some VHT paint will wash off with fuel, even after drying for a long time.
Hope it works!
Will let you know, just wondering if you cured it in an oven and it still washed off with fuel?
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Hi,

I used the VHT in black to paint the barrels on my 72' 450 and found it excellent, it goes on nice and I've not found it smudge or wipe off with any petrol or oil. The head and crank cases were sprayed in halfords own high temp paint in silver/grey which looks fine but I have had to touch up here and there with some wiping off with an oily cloth, in hindsight I should've used the VHT in silver instead...

There's a few pics here on my build thread:
viewtopic.php?t=17644

Hope this helps!

P.S Don't be afraid of a little polishing, it's good for the soul ;)
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Just wanted you to know, koolio, that I think your bike is gorgeous.
 

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Re: Opinions on clearcoat, engine painting and heat retentio

I just checked the Eastwood site...it seems they no longer sell the Hard Diamond clear that I've been using...just the regular diamond clear

Damn...I really liked that stuff...I still have enough for a few more engines though ;)
 

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Discussion Starter #15
Re: Opinions on clearcoat, engine painting and heat retentio

dtsmjr8dan said:
Just wanted you to know, koolio, that I think your bike is gorgeous.
Yours doesn't look too bad itself! :D
 

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Re: Opinions on clearcoat, engine painting and heat retentio

koolio said:
dtsmjr8dan said:
Just wanted you to know, koolio, that I think your bike is gorgeous.
Yours doesn't look too bad itself! :D
Sadly, I no longer own it.
 

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Discussion Starter #17
Re: Opinions on clearcoat, engine painting and heat retentio

Well I had my cylinders bead blasted, then I washed them clean with acetone, used gloves throughout, gave them a blast with VHT black gloss engine enamel, very light coats in between as per instructions.

I'm not pleased with the results, although it looks very good it chips extremely easily, I'm not sure how it will hold up on the road given that I could probably scratch it with my fingernails?

Can't see what I did wrong, although I've read somewhere that acetone will make the oil impregnated in the alu seep out and so the engine should be heated first then acetoned then heated again to expel the acetone? Anyone else concur or had this problem?

I'm now baking it after 2 weeks of it resting in a last ditch attempt to get it's durability up.

It's either something in the prep or the product is rubbish.
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Hi,

I don't think it will work in the end. These cylinders / heads are porous, and if the original paint is gone, oil and dirt will be sucked into the pores and it's difficult to get it out. At the moment I am trying to anodize a few parts, I will report as soon I get the parts.

Jensen
 

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Re: Opinions on clearcoat, engine painting and heat retentio

Koolio i just used VHT on some non-engine parts.
Thought surely it would be super tough.

Got the same results as you.
Looks great. BUT Chips off with my fingernail...painted and cured in oven as directions say.
I know this doesn't help you...but it helps me knowing I am not the only one in the chipping VHT boat.
Am now re-doing.
 
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