Engine Soda Blast after Sand Blasting

[Seaking]

A local shop had me do some parts for them in the soda blaster and they liked how non-destructive the process was to the surface metal. They then asked me if I could do engine parts for them as well.. I went to their shop to see how big the engine was and if it would fit into the cabinet at home here or if I'd have to do it out of the box..

Unfortunately, the engine had already been sand blasted with sand.. and wow, what a rough finish on the engine.. Nice and clean yes, but rough looking. He had hoped soda would 'smooth' that out for him but I know soda won't even touch it..

To help the guy out, is there anything that can be done to get rid of the sand blasted effects on the engine to smooth it out again? Putting it on a buffer would do the trick but you couldn't get into all the crevices and angles required to make it look uniform. What a long process to do all that by hand.. if possible at all?

Would glass bead or aluminum oxide have enough effect to smooth out some of that sand blasted effect on the engine, valve cover etc?

 

[Big R]

Google "vapor blasting". I haven't had it done personally, but the results online look great.

 

[gtermi75]

You may have to step it down through finer grains of sand until you get smooth, for the money walnut shell and soda are the way to go on engines, unless there is heavy oxidation then glass bead or fine sand at low pressure cut it pretty well without trashing it too much.

I would try Glass bead on it if you have access to that....you really can't make it any worse

 

[xb33bsa]

glass beads will change the look,they peen the surface but do not remove metal

 

[Seaking]

Thanks for the replies! Vapour blasting is indeed an impressive process, but not available near here.

Sounds like glass will be his best bet, peening the surfaces flatter and getting rid of what the sand blaster did to the engine. I presume glass will require more CFM / pressure than my system can provide to get the effect desired.. (5.7 CFM at 90 psi)? Haven't tried it yet.. bags are not that expensive, I might try it to see if it will work.

Cheers

 

[xb33bsa]

glass beads do work best with a pressure feed system,but syphon will work,just make sure your cabinet is sealed nicely and dust collector works
no moisture, no grease,no oil
the beads will keep working over and over until they finally work harden and shatter to dust

 

[AlphaDogChoppers]

Glass bead will definitely smooth out a surface roughened by sandblasting. Be sure to set things up to recover your media. Glass bead lasts through many uses before they start to break up, and they aren't cheap. so you will definitely want to recycle them as effectively as possible.

 

[Tim]

Lets take a step back for a minute - is it safe to assume all the mating surfaces in the engine were protected from the sandblasting? I know it's perhaps a stupid question given the fact everyone here knows not to sandblast indiscriminately, but we're talking about an aluminum engine that someone decided sandblasting was appropriate for, so who knows what they did to the critical surfaces.

 

[Seaking]

When I looked at the engine, the mating surfaces did not appear to have been sandblasted. If I remember correctly the valve cover was still on the head. Wish I had taken a photo of it at the time..

 

[krafty]

I don't think I'd ever sandblast an engine, especially anything aluminum. It's great for removing paint and rust from chunks of steel (like my CB350 seat pan... sigh) but it is WAY too abrasive and aggressive for anything else. Beadblasting a clean surface will give it a matte look. I love glass bead for things like carb bodies and other cast items.

 

[Seaking]

I haven't blasted with anything other than soda, love how soda works. My system isn't powerful enough to strip chrome, you need over 10 or 11 cfm at over 100 psi for that, I believe... unless you're working on an early 80' Suzuki.. that chrome will come off with a slight sneeze..

 

[AlphaDogChoppers]

I don't think I'd ever sandblast an engine

Unless of course you are going to powdercoat it.

 

[Seaking]

And THAT is purty!

 

[1sttimer]

If the engine is disassembled already, you may want to PC it like alpha dog mentioned. You won't have to worry about it peeling later and it's already prepped it sounds like.

I think either way you are going to have to do something to the surface to protect it. Textured surfaces will attract grime, whether it's bead or sand blasted. Unless you polish...


Sent from my iPhone using Tapatalk

 

[Andrew21502]

That engine looks pretty awesome

 

[NagChampa]

Unless of course you are going to powdercoat it.

So the rough surface left from sand blasting better for powder coat adhesion than the surface left by glass bead blasting? Definitely will PC my engine but up until now I thought glass was the way to go.

 

[AlphaDogChoppers]

Glass bead gives you peened, almost burnished surface. Definitely not as good for powdercoat. Ideal surface for powdercoat adhesion is given with aluminum oxide as the blasting media.

I have powdercoated some pieces that I bead blasted, because it was convenient. Results were unacceptable. Problems with chipping.

 

[swan]

NEVER sandblast or glass bead any alloy motor parts. Sandblasting is too rough and glass beads embed in to the pores of alloy casings and then will be released later when the motor heats up. The beads will flow through your oil loop, scoring your cylinder walls, cams, valve guides etc.

If you plan to paint your motor, then simply degrease the parts, scuff then original paint, wash with soap and water, paint and then heat treat them.

Walnut shell and soda blasting will clean alloy parts and will wash out with soap and water. After the first time I had parts vapor blasted, I will never use any other method. Here is my 51 year old BSA Gold Star after vapor blasting



Here is a CB400F motor I am working on tonight. I ran everything through my parts washer, scuffed with 3M pad, soap and water, light Duplicolor high temp engine primer, three coats Duplicolor 1615 VHT aluminum and then three cycles of heat treatment (125, 225, 325 F).

 

[Hoosier Daddy]

Swan brings up some points I was going to say. But in short, aside from the appearance issues, He has screwed the pooch using sand.
The sand will get into the engine any way posible. You say it still had the valve cover on so it is at least partially assembled. So now he is going to have to take the engine completely apart and meticuously clean every single piece. See what A.D. is showing he did? Those were not assemblies, but individual pieces.
Even if it was COMPLETLY assembled the sand will still manage to get inside. Taped off all the ports you say? Sorry, doesn't help... the blasting will get past anything short of sealed metal block off plates.
Imagine the exhaust ports, where do they lead? Directly to the cylinder! So the rings are doomed the first time a valve opens. And you will never get it all out. Even with washing and compressed air. A few grains of sand in a main, cam, rod, wristpin bearing surface and a couple thousand RPM and it's going to fail.

If he STILL wants to risk it... I'd recomend he shoot the whole thing with VHT engine enamel, it is already perfectly prepped for paint adhiesion. But he is just putting lipstick on a pig.

 

[rockcitycafe]

I've used glass bead on engines, and learned it from mechanics who used it all the time with good results, the trick is to wash the parts 3 times after beading, using very hot water and soap, and changing the water each time. I've never had a problem with bead damage in an engine I built, but have since looked more into walnut shell media, because washing parts that much is kinda a pain.