cleaning aluminum intakes

[mrrec]

The GM engineer has some good info and I believe a good deal of it applies.

I own a small mfg co and have experience with new alum castings. Not all castings are media blasted, though, after shakeout (removal from the mold) and I don't know what they did in the musclecar era on trans parts and intakes. You can bet there is not one right answer!

Sand castings (intakes, trans main cases) are very bright (almost aluminum paint bright) as cast in many cases. You can duplicate this with an older casting (regardless if it has been blasted before) with a "brite dip" in acid. There are several formulations including 94% Phosphoric acid, 6% Nitric acid. I glass bead first, then dip. Contact time of the acid determines brightness. It works.

Die cast aluminum cannot have the original finish (skin) restored by media blasting. As cast, diecast has a much darker, smoother look. Once you blast it (vibratory, tumbling, media blasting), you're done. I have not found any procedure to accurately replicate this finish (just find a tailshaft housing someone hasn't messed with!).

The "reskinning" thing is a misnomer. You really can't "reskin" (and like the GM engineer said, sand cast aluminum doesn't have a skin anyway). I had McNeish do an intake to see what he was doing and it is appears to be just a media blast (media unkown). I've done the same with glass beads. It does look nice, though.

Cast iron "reskining" by those saying they do that is probably ceramic coating. Sand cast cast iron does have a bit of a darker colored "skin" in some cases. I had a set of exh manifolds for my Z16 ceramic coated in grey, then painted them Chev orange as proper. Hopefully, as the orange burns off over most of the body, they'll reveal the grey and stay that way.

Dave

[Charley Lillard]

Dave...For those of us who are now going out to look for Phosphoric and Nitric acids.... Where to get ? Dangers ? Did time suggestions ? Containers ? Disposal ? Shelf life ? Can we all send you our stuff ?

[JChlupsa]

What ever you do make sure you request a Material Safety Data Sheet (MSDS) when you buy any of the products. Stores are required by law to provide you with one upon request!! Dont just let them tell you that the small 1 paragraph wording on the side of the can is good enough. Its not!!!!!

[CamarosRus]

I have NOT tried the below myself, but read this elsewhere on net......

"A mixture of Chromic Acid and water will clean most aluminum surfaces up really well if used correctly. It will also help to protect the aluminum from corrosion too. Go to a chemical supply house and buy some Chromium Trioxide Chrystals. When mixing, ALWAYS PUT ACID INTO WATER and NOT the other way around! Be sure to wear eye protection such as and protective clothing of rubber or plastic when mixing any acid solutions together. Then put 7.5 fluid ounces of water into a beaker and carefully pour in .4 ounces of Chromium Trioxide Chrystals while stirring with a wooden stick or glass rod. This solution can be used on freshly machined aluminum surfaces or to treat mild corrosion. For areas of heavy corrosion, take a piece of plastic (plexiglass) and scrape the excess corrosion off and not damage the areas that are not corroded. The surface areas must be clean and free of oil or dirt before applying the solution. This solution mixture has a shelf life of about 30 days. Be sure not to dip in dirty cloths or dirty cotton balls into the solution repeatably as the removed corrosion absorbed in these will have a tendancy to kill the power of the fresh solution. When applying the solution onto the aluminum, allow the acid to stand for about 2 to 5 minutes or until it has stopped working (or bubbling), wash off with clear cool water to remove remaining acid and dry with an air hose or wipe clean with a clean cloth until dry."

Chuck S

[CamarosRus]

Dave from Iowa, If you look at the M-21 Tailhousing in above pics....I had that "TUMBLED" in Aluminum media, for a relatively short time. The media looks like pyramid shaped 1/2" Dia Alumninum pieces????. I also had ORIGINAL (not the newer design polished) LT-1 valve covers done the same way.
I WONT say they are "DEAD-NUTS" factory the same, but I gotta tell you they look as good as it gets.......I used a LIGHT glass beading first to remove any misc blemishes...
Chuck S

[CamarosRus]

Bill S, THE same Jeff Betz,indeed. He recently sold his WORLDS BEST 77' Z-28 & extremely impressive 02' Z-28.....and as you said changed direction with an older Chevelle 2 Dr wagon. I've seen pics of NEW 502/502 and Tremec 5-spd. Stand by for further details.....I stayed at Jeff's home during Woodward Ave dream cruise....
Chuck S

[MosportGreen66]

The intake on the Coupe was in good condition to begin with. Mild media blasting... then steel wool and WD40 cleaned it up real nice... The process has held up as well.

[P.J.]

Phosphoric acid and Nitric acid dip is the best nothing cleans aluminum better. I used it in the manufactoring of aircraft tooling for years. You can find a local aluminum
treatment company and ask if they will dip it for you.Those chemicals
are to be handled by pros and with the right equipment. Sand blasting your intake is not recomended as it is like adding sand in your gas tank use glass.
Peter

[NCGuy68]

[ QUOTE ]
Phosphoric acid and Nitric acid dip is the best nothing cleans aluminum better. I used it in the manufactoring of aircraft tooling for years. You can find a local aluminum
treatment company and ask if they will dip it for you.Those chemicals
are to be handled by pros and with the right equipment. Sand blasting your intake is not recomended as it is like adding sand in your gas tank use glass.
Peter

[/ QUOTE ]

I agree, but use plastic media for blasting rather then glass or sand.

NOW...once you have that cast aluminium part looking OEM, how do you preserve the finish?

[hugger_69]

A buddy and I restored an original set of 69 Z covers just last Sunday and here is what we did to them. A light media blast with some real fine glass (worn out), then cut them with Triple 0 Steel Wool under the wash brush in a Varsol Bin. They were then washed down with Brake Clean and here is the end result. They look pretty darn close the factory finish if you ask me?



Graeme