I’m disassembling a 1.7 parts car engine and want to paint the fan housing for a future engine build. After a couple of hours of scrubbing and cleaning I can see metal underneath all of the caked on grease and oil! What’s the best next step cleaning and prepping process before paint? Is oven cleaner ok to use?

Thanks,
Jsaum

Have it tumble blasted, but do not paint. Anything that will inhibit heat dissipation should be avoided on air-cooled motors.

This one was tumble blasted and has returned to its original magnesium finish to tarnish again over time.

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Now I've learned something new today. Had to Google that one. Can you explain the benefit of tumble blasting as opposed to something like walnut blasting?

As per one of the tumbler manufacturer's website, "In tumble-blast batch processing machines, all surfaces of components are exposed to impact treatment as the parts gently turn over and over in a slowly rotating tilted basket.
This design virtually eliminates component damage due to part-on-part impingement that is so common with “barrel-blast” machines. Our tilted basket generates greater circulation of components in the batch, which not only yields more thorough and uniform coverage, but also makes for a shorter blast cycle – typically five minutes or less!"

My local supplier did not disclose the type of media used, however upon completion of the process, the pores of the magnesium are left closed. No need to seal it with clear or paint.

Easy-Off Oven Cleaner works well. And don't paint it.

That looks great.

It is my understanding that cerakote will no hinder heat dissipation. This is a picture of one that I had cerakoted. I don't remember the color.

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Cerikote is good stuff. I’m not sure the fan housing gets hot. Isn’t it’s purpose to bring in fresh air? If so, it shouldn’t be getting hot.

Some had mentioned not to paint or powder coat because heat would not dissipate. The cerakote to me is a good option. I believe there are many applications where cerakote is a very good option. I was shown the booth where he applied it and it had some serious fan and filter, it must be very toxic to apply.

Yes, you need a good respirator.

I googled it and found a shop a few miles away from me. I’ll give them a call and see how much they charge.

It's an impeller (fan) housing and IMHO heat dissipation isn't a critical concern.

I've media blasted and painted several without a discernible change in engine temps.

I agree, I have seen no increase in temp issue with my newly powdercoated fan housing, but powdercoating is thick and may effect the continuity of the ground for the alternator( I am having this issue) But temps are not an issue(oil or head temps)

Phil

That's what I thought. Mag is a pretty reactive metal and I wonder if paining actually increases its lifespan by slowing down corrosion.

totally agree no paint, will flake off after a while and look like crap. Also Porsche painted the sheetmetal black to dissipate the heat better than any other color


quote name='914_7T3' date='Nov 24 2018, 06:00 PM' post='2668357']
Have it tumble blasted, but do not paint. Anything that will inhibit heat dissipation should be avoided on air-cooled motors.

This one was tumble blasted and has returned to its original magnesium finish to tarnish again over time.

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James do whatever will protect it.

If you want to shortcut the process I have both early & late housing already finished.

BTW the Impeller housing was never bare as delivered. It WAS covered with some coating that gave it a slight iridescent gold color from the factory

Probably the same as the trans.

Yep.

Probably some type of conversion coating that was found later to be environmentally un friendly later on. Only a quess.

I know enough about metallurgy to be dangerous.

I've used clear engine paint, and a Dupli-Color cast metal paint with good results. I like powder coating, but getting a jobber that can do quality work with a detailed cast alloy part like this would be the key.

Any coating can come off over time. It's usually the next 5-10 years that matter.

If I went through the trouble and expense of getting one all cleaned up and tumble blasted or whatever, I'd put a protective coating on it. The magnesium alloy should be protected, IMHO.

I think the factory used some type of Cosmoline like coating, but I've been wrong many times before.

I don't know why, but I researched this when I started my resto. The stuff they used was Tectyl 846 which pretty much looks like Cosmoline to me. Like Cosmoline, I expect it to melt off and be gone in the first couple hundred miles. I think it was intended pretty much just to protect during shipping. Here's what it looks like on my block.

Cerikote is good stuff. Especially if it's baked on. You can argue the heat form the engine may do this, but I suspect that you will have zero issues with it, as long as the surface has no grease or crud on it. We use a acid pre treatment when we coat to get all imperfections off. Muriatic acid works well and is readily available. This will give you a finish that will not oxidize or stain easily. Aluminum is porous (especially castings), so the surface picks up crap easily.

The housing is mag. That's why a paint like cerikote is good. It' can be iffy trying to powdercoat mag.

Mahle gas burner wheels are mag and they were primed and painted. They would have looked pretty rough in a short time if left bare.

interesting information about the factory coating. i think just like today, with “lifetime no maintainence transmissions” etc the factory only wants to get past the warranty time as far as making it last. Maybe it was not the best way to go but i bought a fan housing that was cleaned and powdercoated and it looks great. i bought it from Mr. Stone and i still have my original one, i should clean it up but all the oild from the leaking crank seal and all the undercoating are probably protecting it from corrosion.
I guess i can just watch and see how it lasts. it looks great!

I finally got back to this project. After looking at several of the suggested coatings I decided to just go with spray paint. It may flake off in a few years and if so I’ll go with something more durable. I used a lot of degreaser, oven cleaner and muriatic acid to get the surface clean. I the sanded it down with 100 to 200 grit sand paper. I’m happy with th e way it turned out.

Here’s more pictures.

Looks good.

Remember to scratch off the paint where the 4 bolts from the engine mount the fan housing onto the engine case. This is the return (ground) path for the alternator. Also scratch off the paint where the alternator bolts to the housing.

I made that mistake and slowly saw my voltage drop over a 4 hour drive and almost didn’t get home!
That does look great though!

I bead blasted 2 fan housings, and they looked pristine bare.

1 I coated with crc corrosion inhibitor which gave it what I think looked like a factory finish, a sort of golden coat of wax/oil. It's been on a shelf for a few years and it's darkened about comparable to a factory finish. Never actually ran it though.

The other I put installed bare and noticed it was oxidizing, some white rust on the top. I decided to rub motor oil on it, and I think it actually worked pretty well.

Oh dear never thought about that,could that explain why I have had issues with electronic ignition modules,probably not but thought I would ask .

Thanks for the reminder. I figured it would need to ground so I removed the paint at the parting line of each case half and do plan to remove the paint at the mounting points so I’ll have a good ground. I used my ohm meter to check to make sure there is no resistance on the ground tab at the top. So far so good.

What heat dissipation is there on a cool air shroud?
I have sand blasted them and sprayed with silver metallic. The mag will soon tarnish soon.

What heat dissipation is there on a cool air shroud? --- None. The heat dissipation isn't a thing with the shroud. Guys aren't really thinking on this one.

I have sand blasted them and sprayed with silver metallic. The mag will soon tarnish soon. ---Porsche had the magnesium gas burners primered and painted so they would look nice. The same can be done with the fan shroud. I would use a two part paint if you want it to last.