I am in the process of replacing my 2bbl for a 4bbl quadrajet setup on my 72 350. I purchased a period correct cast iron intake and carb from one of our members. In the process of cleaning it all up by soaking in lye and then a good vinegar bath to remove the rust has proven well so far. My question that I have for everyone is if you have done yours this way how did you prevent the flash rusting prior to painting the intake? Very shortly after I removed the intake from the vinegar I could tell it was already beginning to rust again. Any help is greatly appreciated. It is currently sitting in the vinegar again for it's last soak. Here's some photos to show my process.

 

Best way is to blow it dry with compressed air and prime it right away. It should be good until you can paint it.

 

edzolz, how would you treat the inside of the manifold?

 

Soak it with WD40 or CRC

 

Bill, thank you! I was going to use WD40.

 

After a complete cleaning such as you've done, I gave my entire iron intake manifold several baths in diesel fuel.

 

Norm, just to clarify you would diesel bath prior to paint? Does this help with the rust coming back? I am ready to paint it but am concerned that the bottom will rust again prior to installation.

Thanks, Mike

 

I can't say what anyone should do, but what I did was washed my entire intake manifold with a a wire brush & oven cleaner (essentially lye - NaOH). After the oven cleaner washing/scrub, I immersed the entire manifold in diesel fuel several times - I was primarily interested in removing caustic residue from the interior of the manifold. After this I wiped down the entire manifold with cotton towels. I then used compressed air and blew everything out of the passage ways - everywhere. The final item I took two boxes of Baking Soda [Sodium Bicarbonate (NaHCO3)] and sprinkled the entire outside of the manifold top and bottom. I lightly scrubbed the exterior surface with one of those Scotch Brite Pads. The Baking Soda soaked up any remaining residue then I sprayed the entire interior & exterior with a garden hose. Finally, I used compress air to blow dry the entire manifold and painted it without primer with a couple hours of cleaning the manifold. I never experienced any surface/flash rust.

 

I re-read your post - again. Your issue is the vinegar - the vinegar will cause a surface/flash rust. Don't use the vinegar. I may know where you're heading with this and your thinking is sound enough if you're thinking of neutralizing the lye but you're working with Fe (Iron) here. Vinegar is a very weak acid - none-the-less, it is an acid. As such, it will cause rust to form on Fe. While it's a plausible notion to neutralize a strong base (such as lye - NaOH) with a weak acid such as vinegar, you're working with iron and the vinegar will cause a surface/flash rust. So, get rid of the vinegar completely, hose down the entire intake manifold with simple water. Water out of the tap is an extremely weak carboxylic acid. All you need is tap water to remove the lye. Hope that helps.

 

Great information. The vinegar worked wonders to remove the rust but I did wonder what the after effects would be. I'm going to get back on it tomorrow and hope to get it all finalized. Using the Seymour rattle can from OPGI for now as my son got it for me lol. Will post pictures when it's all done. Thanks again

Mike

 

Both Fe2 (Fe++) & Fe3 (Fe+++) [rust] will dissolve in vinegar - vinegar will dissolve (remove) the rust; however, the vinegar will also dissolve the cast Fe (Iron) metal. So, in a nutshell, the vinegar is dissolving the rust before your eyes but forming additional rust. It's a never ending battle when an acid meets a metal. The acid always wins.

 

Here's the final product. Not perfect but it'll do until the time comes when the engine needs to come out. At that point I'll paint everything in Hirsch Gold.

 

Looks good. Enjoy slinging that 55lb slab of iron back on the engine.

 

^^ This is right. I always use my cherry picker to heft those heavy turds.

 

I recall one time in high school I was almost pulled into the engine bay while leaning over the fender and lowering the iron intake into place. I didn't have enough weight to counter-balance that dang intake. I swapped to an aluminum intake mostly due to the weight difference.

 

Yeah this thing is definitely not easy to move around. I'll be making sure my son is around to assist! Looking forward to that Quadrajet though!