Using a needle scaler tool to finish cast-aluminum parts

[Namerow]

There's been a bit of chatter over the last couple of days about positive results achieved with a needle scaler tool for the removal of tar-pad sound dampener from floor panels, and even undercoating from the car's underside surfaces.  That's great information and looks the a a heck of ot more convenient than dry ice, CO2 blasting, scrapers, blow torches and heat guns!

However, I'm interested in hearing about the use of this tool for cleaning and conditioning aluminum castings.  I'm thinking specifically of the Z's valve cover and SU carb bells.  In both cases, the parts don't lend themselves to blast cabinet treatment (because of the size of the part size in one case, and because of the risk of media-particle part contamination in the other).  In addition, the end result from blasting these parts isn't necessarily a correct look -- to my eye, anyway (it's a little too bright and porous-looking). 

I think I recall someone saying that a needle scaler delivers a more OE look for these types of castings (a smooth, 'hardened' surface look, kind of like shot-peening at a miniature scale).  Has anyone tried this?  Any before/after (or even just 'after') pix to share?

[grannyknot]

That's a good question, just went out and found an old cast aluminum engine mount and wiped it off with a rag.
 The scaler was used for about a minute on the left side black line. The first two pics are before,

 

[Patcon]

Yeah.....No.

That was pretty harsh to the casting

Edited December 18, 2016 by Patcon

[sweatybetty]

4 hours ago, Patcon said:

Yeah.....No.

That was pretty harsh to the casting

yep. that's ugly

[Namerow]

Oh well...

Stay tuned for next brilliant idea.

[grannyknot]

Now it could be because the needles on my scaler are still new and still have a sharp edges and that will round off with use.

[Namerow]

I got the idea from our friends at Z-Therapy, who say:

"After the bodies are machined, the carbs get polished.  All ZTherapy carbs are machine polished with a unique high  pressure (22 G's of force) machine polish technique.  This is not a wheel polish.  These carbs shine better than when they came out of the molds.  By polishing in this way, we close the pores of the metal.  They shed dirt better, and look great!"

Maybe they really are using a shot-peening process?

[grannyknot]

Just for fun I pulled out my very expensive Mcgyver type soda baster and basted both sides of that engine mount,

Then with a Q-tip I coated the bottom two quadrants in each pic with GIBBS wonder oil, let it sink in for an hour or so and rubbed the excess off with a cloth.  I don't know if is an original look or not but it's a good look I think, certainly easy to take care of, you just apply more.

[Careless]

13 hours ago, Namerow said:

I got the idea from our friends at Z-Therapy, who say:

"After the bodies are machined, the carbs get polished.  All ZTherapy carbs are machine polished with a unique high  pressure (22 G's of force) machine polish technique.  This is not a wheel polish.  These carbs shine better than when they came out of the molds.  By polishing in this way, we close the pores of the metal.  They shed dirt better, and look great!"

Maybe they really are using a shot-peening process?

FWIW, Bruce did the carbs on the car I'm currently restoring, and the valve cover was done locally with steel shot burnishing process, and they look identical in finish. a touch less aggressive, and it will look exactly like the inside of a cast aluminum timing cover, which are burnished lightly burnished out of the original molds.

If you want to have a closer to OE look, try finding someone who provides vapor blasting services. I had the items vapor blasted prior to burnishing, because prior to that they were sandblasted.

Had they been vapor blasted from the beginning, I think they would have been closer to the dull sheen, rather than high shine that the burnishing provides.

You can prevent media contamination by making a block-off plate for the valve cover out of 1/8 alu and sealing it with RTV. once it's cured, you can remove any bolts used to squish it together and it won't go anywhere. Just be sure to shove a plastic bag into the oil separator inside the valve cover and seal it with duct tape.

At a hardware store, you can find hole plugs for desks and cabinets, decorative stuff that fits right into the oil cap, and can be held on with RTV as well, and you can also get rubber plugs that can be RTV'd into the PCV tube, you can shove a small plastic bag in there too before sealing it up.

It will come out as clean as it was going in.

Edited December 19, 2016 by Careless

[Namerow]

Thanks, Careless. Now I remember reading the write-up you did on this in your own thread (maybe that's where I got the idea). 

So are you saying leave out media blasting altogether and use vapor blast + shot burnishing instead? 

Or are you saying to change the order of steps so that it's:  vapor blast, then media blast, then shot burnishing?

Also:

Those are great tips for the valve cover.  Now let's talk about the carbs...

• I can easily see similar materials and strategies being use to seal off the bells and the float chambers.  Did you do this?
   
• I'm not so sure about the carb bodies.  Did you use blank-off plates sealed with RTV across the air inlet, air outlet, and top (bell) opening?