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MG MGB Technical - Engine paint and Coolants

Having a real problem with trying to keep my engine paint from being damaged by coolant. I am using MOSS paint and it turns color when today;s coolants hit it.

Have not tried some of the other paints that have been recommended in other lists, but wondering if others have the same issue with non-moss paints?

Would like to find one that others have had good experience with prior to repainting the engine and valve cover.
Bruce-C

Bruce-
Hirsch has an excellent thermoconductive engine enamel that, being unique in that it was originally formulated for use on jet engines, will withstand temperatures up to 600° Fahrenheit and is an exact duplicate of the shade of red (“MG Maroon”) used on the 18G, 18GA, 18GB, 18GD, 18GF, 18GG, 18GH, 18GJ, and 18GK Series engines. It remains glossy almost indefinitely and can be applied directly to cast iron without primer. It is famous for being used on about 90% of all of the winners of the Pebbles Beach Concours, so you can rest assured that its appearance will be first-rate. I will not paint an engine with anything else. Hirsch has a website that can be found at http://www.hirschauto.com/ .
Steve S.

Thanks Steve. I ordered a can so I can repaint my valve cover to get rid of the nice yellow streaks where some blowback off the radiator overflow got on the valve cover.
Bruce-C

Bruce-
Glad to help. You'll like the results so much that you might be tempted to pull the engine and repaint it! By the way, Hirsch is the only outfit that I know of that still sells a show-quality high gloss nitrocellulose lacquer.
Steve S.

Thanks for the link, Steve. I just ordered a quart myself.

Paul K

Paul-
Since you're ordering a ful quart I take it that you intend to paint the entire engine. Here's some tips:

Under no circumstances should hydrochloric (muriatic) acid be used to remove rust from any of the engine components. It will chemically interact with the rust and impregnate the remaining iron surface with hydrogen, resulting in hydrogen embrittlement of the metal that will lead to cracking. Instead, use Naval Jelly, which contains phosphoric acid. Being a thick gel, it will cling to the surface being treated instead of running everywhere as an acid in liquid form would. Hydrochloric acid reacts with the iron oxide (rust) to form soluble ferric chloride, thus leaving a clean exposed metal surface. However, it then also reacts vigorously with the iron to form ferric chloride and hydrogen. If you leave an iron engine block in a bath of hydrochloric acid long enough, you’ll just have a bath of ferric chloride (and enough hydrogen for a Zeppelin!). On the other hand, phosphoric acid reacts with the iron to form ferric phosphate, which adheres to the surface. This protects the surface and also slows down the reaction, so it is more or less self-limiting. Phosphoric acid reacts very slowly with iron, thus hydrogen emission is much lower and hydrogen embrittlement of the metal is insufficient to present a significant structural problem that can result in the formation of cracks.

After removing the rust, rinse the naval jelly off thoroughly, then blow the metal dry with compressed air or your wife’s hairdryer (she won’t mind you borrowing it for such a noble purpose). Do not be surprised when you notice a dark-purple-hued, thin passivated layer of ferric chloride where the phosphoric acid has removed the rust. This is a natural result of chemical interaction. Apply a coat of WD-40 to the coolant passages inside of the cylinder head and to all of the oil ports. Once this has been done, take care to prevent machining chips and machining dust from getting into ports and passages by blocking them off either with rubber plugs (available at most better hardware stores) or with short lengths of wooden dowel rods.

Purchase all of your seals and gaskets well in advance before you start the reassembly rather than waiting until just before you start (as most people do). Using the gaskets and seals as templates, draw around them on wax paper in order to make cheap cut-out silhouette copies of all of them, then tape or glue a stiff tab onto an edge of each of them so that they can be easily peeled off of the surface immediately after the painting of the engine block. Why go to the effort of making cheap silhouette copies? Because the copies can be used to precisely mask off all of the sealing surfaces prior to painting the engine block. Simply smear a coat of petroleum jelly to one side of the copy and place it over its sealing area on the engine block. While it is true that many people simply spray paint the entire surface of the engine block, including the gasket sealing areas, this is a bad practice. Such engines tend to ooze oil around their gaskets because the gaskets cannot achieve a proper seal against a smooth, glossy surface. Gaskets do a much better job of sealing when applied to bare metal surfaces that are machine-finished to the proper surface texture that is achieved during manufacture at the factory. Instead, all gasket areas of the engine should be masked off prior to painting so that the gaskets will have a metallic surface to seal upon. Failure to take this step will likely result in oil oozing from under the gaskets. Once the petroleum jelly is applied to the surface of the gasket, place the gasket onto the engine and then apply the paint. After applying the paint, remove the gasket and allow the paint to dry thoroughly, then remove the remaining petroleum jelly with alcohol. Getting this detail of the rebuild prepared in advance will make for a more oil-tight engine. Unfortunately, few commercial shops will take the time to make this extra effort, despite the fact that they know full well that factories do not paint an engine until after it is assembled. Most owners who are faced with doing the reassembly themselves usually omit this step of advance preparation and simply paint the entire engine block and head in ignorance of proper procedure, only to end up living with an engine that oozes and leaks.

Prior to painting the engine components, be sure to mask off the outer walls of the cylinders, all bearing mounting surfaces, the crankshaft main bearing cap seating surfaces, and the gasket areas, and then apply a coat of thermoconductive enamel engine paint onto the exterior surfaces of the engine block before it has a chance to rust again. Do not allow paint to get onto any of the gasket mounting surfaces or into any of the threaded holes. The outer walls of the cylinders should then be prevented from rusting by smearing their surfaces with WD40, then covering them with WD40-soaked paper until the time arrives for reassembly of the engine. After the machinework on the engine block is complete and the interior and the oil passages have been cleaned out thoroughly, be sure to paint the inside of the crankcase area of the engine block as well as the interior of the oil sump with Glyptal, a coating that is highly resistant to oil. This is recommended to promote drainage of the oil down the inside of the engine block and out of the oil sump as a deterrent to the buildup of carbon and sludge. This is what the factory did. It will also seal the pores of the iron, thus preventing any deposits or metallic machining dust remaining in the pores of the iron after cleaning from leaching into the oil. Because the electric starter motor needs a solid electrical ground in order to work properly, do not paint either the gasket area of the rear of the engine backplate where the starter motor mounts or the area of the front face of the engine backplate where it mates up with the gasket on the backside of the engine block.
Steve S.

Paul-
I almost forgot:

In order to etch the surface for superior paint adhesion, always use a good quality metal conditioner. I use POR-15 Metal Ready, as it removes light surface rust and leaves a zinc coating on the iron metal surface that will inhibit the formation of rust.
Steve S.

I had Progress Paint Manufacturing Co. in Louisville, KY mix some for me. I took them a piece of the engine and asked them for something that was not quite as purple as my sample. They mixed me some industrial coating, and I now have 10,000 miles on it. I have pressure washed it once, and the color on the head right next to the exhaust manifold still looks like it did the day I put it on.

I have never had good luck with anything that came in a spray can. I have had better luck with porch enamel that came in a quart can that I could mix and shoot with a gun.

Charley
C R Huff

This thread was discussed between 19/07/2008 and 20/07/2008

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