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Discussion Starter #1
I have a friend that just bought a 400 block for his '66 Lemans restoration, and it's got a bit of surface rust all over it (cylinders, lifter bores, etc.).

Does anyone have a good idea on how to clean it and remove some of this rust? Is this something that a good machine shop can do, and if so, what's the process called? I realize a hot tank will only remove paint, grease and the like, but is there some similar process for rust?

A web search returned a page that said to clean it with muratic acid, but wasn't very detailed in regards to measurements and soaking time, so we're not brave enough to try it.

Any help is appreciated!
 

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There are a lot of machine shops that wheel-abrade blocks for about $50......They look brand new after that......
 

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I use Muratic acid - only I don't dip. take a regular spray bottle and mix the acid with 50/50 water. Spray on and then spray off with a garden hose until the rust is completely gone. This may take 3 or 4 applications. once the final application has been hosed off, spray the block with a good mixture of warm water and baking soda to neutralize the acid. If you have it, blow off with compressed air and then spray the entire block with WD40 to prohibit reaccumulation of rust. the nice thing about this method is that you can get inside of the water jackets (make sure you have pulled the freeze plugs out first) and it gets ALLL of the rust.....

randy
 

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If the c-bores are rusted be sure talk with your local machine shop about their tank. Acid dipping a rusty block will clean up the rust but pit the bores requiring them to be bore out further to get them cleaned up. A true hot tank will not remove any metal. I found this out the hard way my first time around. The last thing you want to have to do is to build a fresh .060 over motor.

Good luck,

Pat
 

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I've heard you can soak a block in a 10% muratic acid solution for 4-5 hours and the rust will be gone.

"Hot tanking" a block at the machine shop will not remove rust. The liquid in the hot tank is a very strong caustic solution that will dissolve grease, dirt, paint, aluminum, but won't do diddly to rust....
To dissolve rust you go to the other end of the litmus scale and use acid. The drawback to acid is that it attacks the metal almost as fast as it dissolves the rust.

I prefer flex (ball) hones to clean up rusty bores.
 

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Discussion Starter #7
Thanks to everyone for the advice. I think we're going to try the acid cleaning this weekend.

Thanks again!
 
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