Projects rust in water jackets, Oxalic acid question

I've got an old mopar 318 block. When I pulled the freeze plugs, the block was full of mud/sand/crap. I've cleaned it out best I can.(pressure washed, dug out as much as I can ) (by the way this is a bare block on the stand)
I seen an old post about using Oxalic acid to remove rust. My question is/ if I install my freeze plugs, then pour the Oxalic acid into the water jacket ports through the head gasket deck holes. Will it cause any damage to the New freeze plugs ? Will I have to replace all the freeze plugs again ?
Also how long should I leave the acid in the block ? Do I have to neturlize the acid afterwards ?
What about using CLR rust cleaner ?

 

take it and have boiled out

 

x2 ^^^^^^

 

I have a tub of oxalic acid I soak parts in. If your block is that bad I'd either leave it in there for at least 3-4 days...won't hurt anything to sit longer. Neutralize with baking soda & water. I'd pop the freeze plugs to clean it out and then put new ones in for final assembly.

 

I would have it boiled or baked out .

 

I do not have a tub large enough . thought of just pouring into coolant holes at head surface/ with plugs in. How strong would I mix the O acid ?. And how much would I need to buy ?

 

I've often wondered if sloshing that acid, or white vinegar, or swimming pool acid, around in a sealed up block would do a better and quicker job than even a hot caustic bath from an automotive machine shop.
Here's a crazy thought: since you are a machinist, could you not fabricate a device that joins that part of your engine stand to some of the lug nuts of the rear wheel of a farm tractor? Fill the water jackets (heads and intake installed, water pump and thermostat holes capped) and drive around for a few minutes, park it a few hours, repeat the process for a few days. Drain the solution, remove heads, intake, etc. and high pressure wash out the "crap". May have to repeat the process.
Seems to me, there are guys over on Ford Barn using this method for de-rusting Model A gas tanks.

 

Any acid can remove the rust (aka iron oxide). Any acid used should also be neutralized, and baking soda is cheap and effective. Weaker acid will just take a longer time, so even if you have to make up a garbage can to fit the block into, a 5% solution will work for example. Some agitation will help, but it could be simple as just lift and turn the block each day. You may even have to do each end separately, but best to completely submerge it if you can.

Not to be a safety nanny, but reminder always add acid to water. And wear protective gear for eyes and skin.

 

Shake & bake is the way to go if you do use the acid why not just put rubber expandable (hdwr store) plugs so you can remove them when you are done. I don't think a week would hurt.

 

What about using vinegar?
It sounds perfect for your needs and concerns.

 

I used muriatic in my 327 out of my 63 think it was about a 50 50 mix didn't take long I poked around in the water jackets with a welding rod. Looked like brand new when I was done.

 

There can be a lot of crud in there.
How much ?
Well I did a block on the cheap so i rigged a hose into the front water pump outlets. With the freeze plugs out, water running thru the block and with two of us on rods, wires, bent coat hangers and bottle brushes poking thru the deck holes it took almost 3 hours for the water to run clean. Just when the orange ness was slowing down, We dislodged some huge chunks that needed to be broken up to fit thru the maze of passages to make their way to the freeze plugs - Not too much fun. What's behind that chuck needs scraped loose all over again.

So much crap came out of there it stained the black top orange for a month. This was done outside on a summer day. We were both soaked. When we were done and the water ran clean, the inside looked almost new- not quite perfect but pretty damn clean.

Now I soak parts in vinegar and oxalis acid all the time. There's no way that either will brake down the crud enough that you don't have to nock it off anyway. There's no way a soak only on the block I did would have worked.

Your mileage may vary.

 

Oxalic acid is in the same family as vinegar but quite a bit stronger. I got my baking soda & acid from http://www.vandykestaxidermy.com/. Mine is mixed 2% by weight...water weighs 8.33 lbs/gallon. Example would be 10 gallons of water which would weigh 83.3lbs so you'd need 1.666 lbs of acid.

Here's a water neck I cleaned up off of a '58 John Deere 520:


I soaked it in lye to remove the paint then in oxalic acid for probably 3-4 days. I washed it out really good with water then lightly bead blasted it:


Doesn't take much blasting at all to look like that. Without blasting it will be tinted yellow.