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Scale build-up in head

shoptek

Registered
How do you clean the scale out of a head in a hit or miss. Mine looks like it has built up to the point that some of the small ports around the spark plug, exhaust port and intake are plugged. do you just try to scrape it out or muratic acid or what . Thanks
 

IronCity2006

Registered
Last Subscription Date
cancelled
Re: scale build-up in head

Go to wal mart get some vinger mix 3 parts water to one part vinger, let soak, should do the trick. Check part often
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Re: scale build-up in head

Do not use muriatic acid!! I know a guy that ruined a whole engine block trying to clean it with acid. The engine block crumbled. The acid gets in the pores of the cast iron and keeps on breaking down the iron after you think you've gotten it free of the acid.
 

KeithW

Registered
Age
64
Re: scale build-up in head

Depends on what the scale is. If it's minerals I would agree with the vinager. If it's rust you might try phosphoric acid at 10% concentration. I found it labeled as rust remover at a commercial cleaning supply store. I diluted it to 10% with distilled water. I soaked the water jackets of the Ajax with it. No bad effects so far. When it was done I flushed them with hot water then filled them with baking soda and hot water. This would take care of any remaining acid.

If things are very rusty you could run into problems. It's possible that the rust is filling up holes and preventing leaks. Once the rust is removed the holes will be opened up and it will start to leak. There were spots on the Ajax where I had to fill up craters with JB Weld after the rust was removed.

keithw
 

KeithW

Registered
Age
64
There were spots in the water passages where once I removed the rust by various means that the remaining iron looked a lot like a sponge. The corrosion no doubt worked it's way along the crystal boundries leaving a porous surface.

keithw
 

Forrest A

Registered
Removing the scale, exposing bare metal will set it up for corrosion. Water pipes last far longer if they are covered in mineral scale. I would assume the same would be true for you old engine(s). If you are just using the engines at shows with no load and the passages are somewhat open there shouldn't be any problem. If there is blockage though, using vinegar is probably the safest but also should be rinsed thoroughly with hot water once the blocked passage is opened enough to allow water through. I wouldn't remove all of the scale...
 

Beanscoot

Registered
Scale build-up in head: Yes, it happened to me but went away after I stopped watching TV. :bonk:

At the industrial complex where I work we have a chemical cleaning department. Cast iron and steel are cleaned in a many step process:

1) Vapour degreased with chlorinated solvent.

2) Paint and such remaining removed in hot caustic soda tank.

3) Rust stripped in hydrochloric (muriatic) acid tank. Probably there are inhibitors in this.

4) Neutralized at least half a day in caustic soda tank.

Of course there's rinsing, etc. between steps to keep solutions clean. Parts after this treatment have no particular urge to rust. I certainly have seen the rust devils appear in old salt water cooled engines however. You can grind a head or block clean, then next morning there will be more rust in numerous spots.

I think the HCl is okay so long as it's not on longer than necessary, and is completely neutralized. Also the casting should be completely dismantled so there's no crevices in which chemicals can get trapped.
 

PaulGray

Subscriber
Last Subscription Date
12/24/2019
Simple- heat it!. Bake it to 700-800F for an hour and slow cool. All the scale will flake right off or easily with a light bead blast. Also- if you have any cracks or holes, this will find it. If you find an old self-cleaning oven on the curb, that'll work. I have a kiln I use. Have descaled some really far gone oilfield engine cylinder jackets no problemo. All this scale is hydrated calcium/alkaline compounds; remove the water of hydration, scale gone. Most stuff I just hit with a wire wheel and it comes out squeaky clean. Make sure you SLOW cool. ;)
 
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