what is correct color of black for norton 850 barrells

I am about to paint my 74 Norton commando barrells I dont know whether to use a gloss or flat finish on them It's hard to tell from pictures if they were flat or gloss in original condition. Any input on this would be appreciated. Thanks Drummer99

Flat black is best for heat transfer, but gloss is original. If you are strict for originality, do not worry about slight advantage of flat over gloss.

You could compromise and go with Satin Black. I like it much better than flat.
Jaydee

I used this in Gloss Black, it kinda mimmicks the original porcelain like finish inasmuch as it's a high build finish. Has proven very durable. http://www.vhtpaint.com/products/caliperpaint/

concours said:

I used this in Gloss Black, it kinda mimmicks the original porcelain like finish inasmuch as it's a high build finish. Has proven very durable. http://www.vhtpaint.com/products/caliperpaint/

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Respectfully, Concours, I personally would avoid high build finish as it reduces conductive heat transfer (greater thickness thru which heat must travel), as well as convective heat transfer (by eliminating surface roughness which enhances convection). I think the porcelain finish was a case of marketing trumping engineering.

As a compromise, I plan to polish the edges of the fins on my barrels, paint the fins flat black, and the edges gloss black. Do not polish the fins themselves.

There have been threads on this subject recently. Use the search function.

Slick

texasSlick said:

concours said:

I used this in Gloss Black, it kinda mimmicks the original porcelain like finish inasmuch as it's a high build finish. Has proven very durable. http://www.vhtpaint.com/products/caliperpaint/

Click to expand...

Respectfully, Concours, I personally would avoid high build finish as it reduces conductive heat transfer (greater thickness thru which heat must travel), as well as convective heat transfer (by eliminating surface roughness which enhances convection). I think the porcelain finish was a case of marketing trumping engineering.

As a compromise, I plan to polish the edges of the fins on my barrels, paint the fins flat black, and the edges gloss black. Do not polish the fins themselves.

There have been threads on this subject recently. Use the search function.

Slick

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I fully agree and considered the heat transfer issue. But, I reasoned, I ride at parade speeds like an old duffer, so never make much heat :mrgreen:

The factory ones I've seen were a type of semi gloss stove black. Unless holding WOT a long time even thick powder coat works good enough. It for some reason your engine makes like double normal heat fuel burn then look into the weapon coats that are very thin such a GunKote stuff and others. Many were sliver painted too so black for normal Norton heat is just for show trying to mimic a hot creamer of the crop Combat.

My '74 is a gloss black from the factory. As for the concerns of heat rejection, the bulk of the combustion heat goes out the head, so the barrel paint doesn't play as big of a role as we might believe. Looking at VW and airplane engines, the largest fins and highest bulk of airflow is directed over the heads.

Drummer99 said:

I am about to paint my 74 Norton commando barrells I dont know whether to use a gloss or flat finish on them It's hard to tell from pictures if they were flat or gloss in original condition. Any input on this would be appreciated. Thanks Drummer99

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Are you building a "concourse" mcycle or a m/c that is dictated by a budget. IMO, if your doing the concourse thing , keep researching..

If your doing a nice refurbishment with a practical requirement as opposed the to a "show" bike just paint it with "pot belly black" (heat proof flat black)...

There are bigger and more crucial decisions to make than the "barrel paint finish". Unless of course your doing a concourse restoration....

Drummer99 said:

I am about to paint my 74 Norton commando barrells I dont know whether to use a gloss or flat finish on them It's hard to tell from pictures if they were flat or gloss in original condition. Any input on this would be appreciated. Thanks Drummer99

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I like the deep gloss of 'smoothrite' and have used it a lot on barrels.

I'm using Smoothrite on my 850 barrels. But I'm going for silver... oooh, I'm such a rebel... :mrgreen:

Gloss Black Rust-O-Leum gives great coverage, and guarantees you won't have rust peeking through in a few years.

Nater_Potater said:

My '74 is a gloss black from the factory. As for the concerns of heat rejection, the bulk of the combustion heat goes out the head, so the barrel paint doesn't play as big of a role as we might believe. Looking at VW and airplane engines, the largest fins and highest bulk of airflow is directed over the heads.

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The piston clearances in aircraft engines are much larger than that in motorcycle engines.

When motorcycles overheat, the pistons seize in the barrels....that is where the critical conditions lie.

I dare ya to post a report of Norton heat sezure d/t some show off barrel coating. I have read reports of polished engines over heating d/t reflecting IR photons back into engine as much as your reflection outward. If sitting in still air hot direct sun in traffic jam at idle you will see engine cool off compared to heating by fuel to just move 10 mph. Speculate all ya like and admit ignorance on this heat subject but putting temp sensors in oil, head and exhausts will educate up to hobot heat factors speed.

texasSlick said:

The piston clearances in aircraft engines are much larger than that in motorcycle engines.

When motorcycles overheat, the pistons seize in the barrels....that is where the critical conditions lie.

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Sure that's where they stick, since nothing else in the engine has aluminum running inside iron with the different expansion rates to contend with. If it wasn't for that, the next most likely thing you'd see from overheating is the exhaust seats falling out of the head.
As for clearance being larger on aircraft engines, that's merely a function of the larger pistons than we're used to dealing with, plus they're typically forged, making them much more susceptible to swelling with heat. That, and the fact that aircraft engines are usually limited to 2500 max rpm. This drives the BMEPs (Brake Mean Effective Pressure) through the roof, with subsequent piston crown temp spikes. Our Nortons are actually less stressed than aircraft engines, due to the fact that we can spin them up higher. I know that seems counter-intuitive, but, to get horsepower from a given displacement, you need either RPM or torque, and torque can only come through higher cylinder pressures.
"Most" air cooled engines with cast pistons run around .001" inch clearance per inch diameter of bore, and our Nortons follow this same guideline, as the 3" bore clearance is around .0035" when renewing. If you were to go with forged pistons, the clearance will go up noticeably. Case in point; JE spec's .0055-.006 for their forged slugs - just about double for stock cast units.

I like the PJ1 gloss black spray. It seems to hold up very well on my cylinder barrels. I spray a bit into the cap and then use a foam swab (Q-tip will work but may leave a little fuzz) to dab it on the inner surfaces of the cylinder barrel for a few coats before spraying. I've found that the spray cans tend to load up the outer fins but only leave a thin coat on the inside surfaces. This encourages the rust. Eventually it will be damp out or you'll get caught in a rainstorm if you ride much. Example - the INOA Endless Mountains Rally in PA.

Russ

Well, I don't wish to tempt the Gods, so I 'll paint my barrels black for best theoretical heat transfer.

As for Hobot's dare....I seized a piston in my Atlas (that is a Norton, Hobot,) after taking it for a ride onto the Bonneville salt flats, not knowing the salt is dry for a short window of time. The brine spray turned the barrels white when it dried. I made it out of the high altitude country, but when I hit the lowlands and the air temp warmed up, it was critical . The Atlas finished a two-way transcontinental trip in the back of a U-Haul trailer. I was running the original 7.5 CR pistons at the time....expect higher temps with higher CR.

And in case anyone may think the salt plugged my fins.....not so, mostly just turned them white.

Slick

Well gosh Slick I hardly ever do summer salt lake land speed runs on a factory Norton but glad others are now warned how close any Norton is to heat stroke. Peel could of though as equipped with 4 mud-grit-grime-salt flaps so nil extra coatings. I like to see-feel the glossy black barrels on others and the extra shine many folks obtain but it ain't factory spec so not for plain ole Trixie and fancy pants Peel ain't a Norton 'only' a Commando so whole engine is dullish black IR emission coating covered. Its hard to beat engine or stove grade rattle can for easy touch ups I found.

I used PJ1 Satin Black Barrel + Engine Paint. I also polished the fins of the head.
I think the satin finish strikes a nice balance between BBQ Black and "too shiny" Gloss.
Very pleased with the way it looks.

Mark

It would seem that any point is worth an argument. So not being able to resist, I guess here is my two cents. It's an air-cooled engine. Why wouldn't I want to do what I can to help it shed heat? With that idea I bought heat dissipating paint from Tech-line. I suppose now I will suffer an engine failure because the ZDDP in my oil didn't stay warm enough, but I will take my chances. I don't think Tech-line is still making this paint, which is not completely comforting but I did find this:

https://www.duplicolor.com/products/enginePaint/

Duplicolor is readily available at lots of retailers and they offer gloss black, semi-gloss and low gloss. Unless you want to try something like Lime Green.

I don't know what would match the original the most closely but I suspect the semi-gloss wouldn't be a bad choice.

Russ

I'd argue the rust inhibiting compounds in Rust-O-Leum paint are more significant (relatively speaking) than any heat-dissipating properties of the others.