I got a good deal on an ECZ-9425B manifold and I'm in the process of getting it prepped for paint to put it on after smoothing out the venturi holes a little...

Is there something I can soak it in that will get rid of the rust in the thermostat area, as well as any other surface rust as well as the heat riser ports?

Thanks.

I know that I will probably get some negative comments in response to this post but soaking the manifold in muriatic acid (ordinary pool acid) for a few hours will get rid of all of the rust inside and out and will not harm the cast iron.   Just neutralize the acid residue on the manifold with fresh water, dry it off and paint it quickly as it will start to rust almost immediately.  I have used this process a couple of times with no problems.  Home Depot or Lowes sells the acid and you can pour it back in the container when finished and save it to reuse it again.

Depending upon the amount of rust, you might consider having it media blasted; just make sure that there is no residue remaining before you install it. For paint I used Seymour primer and Ford/Chrysler Red Engine Paint for my 55 Tbird; it's the best rattle-can paint I've used, but make absolutely certain there's no residue on the intake before painting. I used Goof Off and 91% isopropyl alcohol. 

Another good idea would be to use electrolysis. For something as small as an intake manifold this will be easy to do. 

I explain the process in the article below. 

https://www.hotrodreverend.com/post/rust-restoration-preparing-a-cast-iron-exhaust-manifold

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

Thank you...three great ideas.  
Daniel- do you think the electrolysis was worth doing, since you ended up blasting it anyway?  It looks like a cool process.  

The electrolysis works well if you are willing to be patient with it. I was in a hurry to finish that up and post the article/video on my website. One of the issues as well was trying to save the heat riser on that setup. Since the gaskets and corrosion were keeping the electricity from flowing from the manifold to the spacer it took more time to be in the tub. I would assume that an intake manifold will not be near as bad as an exhaust manifold that came uncoated/unpainted from the factory.

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

I may just try to have it blasted somewhere.  It's not as crusty as I thought...it's just dirty...I soaked it in Simple Green overnight, wire brushed it and used the drill attachment...soaked it again.  Today I was looking closer and there's still dirt build up all over it.  The Simple Green worked wonders, but I'm getting frustrated.  I'm thinking getting it blasted will clean it all up and then I'll be able to paint it.  

I have sandblasted both cast iron intakes and aluminum intakes before porting them for the last 37 years without any issues.  You definitely have to pressure wash out the ports backwards and forwards afterwards, but media/sand/black beauty does a much better job of cleaning the rust and scale.  Do NOT glass bead the interior of either intakes for the glass beads will break upon contact if there is too much air pressure, and the glass will eventually break free with fuel/air and heat cycles of the engine running.  Glass beading the exterior and pressure washing is acceptable if you tape over the ports and water passage, and carb plenum and use low pressure air.  In the exhaust passages, use sand only or high pressure water.  Joe-JDC

JDC

Thanks Joe,
Should I get 80 grit or 120 aluminum oxide…or something else?
Thanks

Which ever one you have, adjust the pressure to get a rough texture on the ports after the rust and grease is removed.  I personally would use the 80 for cleaning up, and then move to the 120 to give a uniform texture to everything.  It all depends on how show worthy you want the finished product to look.  Wash thoroughly, blow dry or sun dry, and prime asap.  Two or three light coats of paint are better than a thick coat.  Thick chips.  BTDT.  Joe-JDC

JDC