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Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

General engine tech -- Drag Racing to Circle Track

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Eagle1903
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Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Eagle1903 »

Dear Friends,

I am in the early phases of building my vapor blasting cabinet. And I am planning to use the cabinet for blasting engine parts as well as other parts.
But, apparently there are mixed thoughts about blasting the pistons ( especially the skirts ) in vapor cabinet with fine/finest glass beads ( not the crushed glass )
Naturally, cabinet makers show complete piston blasting in their YT videos but some people seems to disagree with using glass beads ( although suspended in the water ) on the skirts and cam tunnels which is the direct bearing surface on alloy cylinder heads. Their reasoning is; although the vapor honing is a very gentle process and the glass beads are not directly hitting the surfaces since they are suspended in the water, it can/may still change the surface roughness on these delicate surfaces. These people says that certain amount roughness is built in by the piston ( or head ) manufactures to hold oil and create the needed lubrication.
So, I am confused.
Are you guys using vapor honing cabinets in your engine internals successfully ?
I have also seen a video showing soda used in the vapor blaster even though it is much less efficient, but works to a certain extent.

Regards
Kerem
Dan Timberlake
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Dan Timberlake »

New or used parts ?

A new modern piston should have magnificent finishes on the ring groove upper and lower sides for best sealing.

I'd fear ANY blasting media would only degrade that important finish to some degree.

In the days before coated piston skirts I believed some piston texture was a good think. Note TRW's wavy skirt finish.
Also note the TRW finish maintained some significant "plateaus" to actually contact the cylinder wall.
Coarse glass bead peened piston skirts usually looked great when later removed from service, with a "plateaued" look much different than the fresh peened surface. I'm pretty sure life was a little harder for the piston and maybe even the cylinder and rings until the zillion aluminum high spots were
buffed off and flushed away.

Then there was the question of embedded Krap. Never a good thing, and probably not completely removed by any solvents or even mechanical scrubbing.
dannobee
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by dannobee »

This is a Porsche 911 case that was vapor blasted. When the oil galley plugs were removed, this is what came out.
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Eagle1903
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Eagle1903 »

Dan Timberlake wrote: Sun Nov 15, 2020 9:23 am New or used parts ?

A new modern piston should have magnificent finishes on the ring groove upper and lower sides for best sealing.

I'd fear ANY blasting media would only degrade that important finish to some degree.

In the days before coated piston skirts I believed some piston texture was a good think. Note TRW's wavy skirt finish.
Also note the TRW finish maintained some significant "plateaus" to actually contact the cylinder wall.
Coarse glass bead peened piston skirts usually looked great when later removed from service, with a "plateaued" look much different than the fresh peened surface. I'm pretty sure life was a little harder for the piston and maybe even the cylinder and rings until the zillion aluminum high spots were
buffed off and flushed away.

Then there was the question of embedded Krap. Never a good thing, and probably not completely removed by any solvents or even mechanical scrubbing.
Used pistons, dismantled cylinder head.. Vapor ( or wet ) blasting machine producers promoting the idea of using vapor blasting ( wet blasting) more and more nowadays. Certainly, these machines with the correct media makes a great job for cleaning, deburring, removing stains, oxidation, polishing especially on alloys.

However, I have doubts about using vapor/wet blasting on certain internal parts as I mentioned.

They claim that glass beads suspended in the water will not embed as long as they turn into crushed glass. Even if the beads become crushed they will still not easily embed.

By the way, I think I know what you mean about the TRW’s skirt finish. Even today some custom piston manufacturers make the skirt with some sort of plateau texture if they are not coated with today’s modern coatings.

But, I fully understand you.

I thought wet/vapor blasting used widely in USA and people did their own research ( surface analysis ) so there would be some definitive results showing if the skirt or the cam journals wet blasted with glass beads then the surface finish changes in a negative way or it doesn’t get affected etc.
Eagle1903
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Eagle1903 »

dannobee wrote: Sun Nov 15, 2020 9:25 am This is a Porsche 911 case that was vapor blasted. When the oil galley plugs were removed, this is what came out.
Not so good !! But wouldn’t be a good idea to block the oil galleries prior to wet blasting?
However, the media can always get stuck in the other crevices of any engine block and it can get extremely difficult to take it out or other time consuming methods negates the nice finish of vapor/wet blasting.
Parts with crevices and some engine internals like pistons and cylinder head journals has always been raising a question in my mind. But the finishes achieved by vapor blasters with correct media is definitely the best in terms of renovation parts.

By the way, what techniques you have used to get all that media out from the case ? ( I guess first pressure washer then manual wash with brushes )
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by dannobee »

That wasn't one of my cases. I refuse to clean anything that has oil passages with vapor blasting. Instead I use either chemicals or dry ice blasting.

You can do a respectable job cleaning aluminum with commercially available "chrome wheel cleaner," but need to be diligent on the time factor. Leaving it sit too long will etch the metal. Done properly the finish looks like it came from the foundry. More "factory finish" looking than sandblasted.
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KnightEngines
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by KnightEngines »

How about "hell no"

Never, ever, ever blast pistons or bearing surfaces with anything containing glass media.
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Momus »

The piston and journals will become a highly effective lap...
Eagle1903
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Eagle1903 »

Clearly understood and I was right to question the process.
Many thanks for your kind replies and for the advise of using chrome wheel cleaner. That is a really beautiful result.
Very interesting to see some vapor/wet blasting companies promoting the idea of using the process on engine internals including the complete cylinder heads. They should not.
Eagle1903
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by Eagle1903 »

Is it also definitely No No using soda in the wet blaster in your opinion?
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by sbcharlie »

I offer vapor blasting services. sad now ever back yard low dollar people are offering this service. we offer the service 2 ways, you clean the internal parts or we can offer this service. I always thought the engine builder was to inspect and check all passages.. as far as pistons we tape the skirts and do the ring lands and piston domes.. sbc
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by DCal »

sbcharlie wrote: Thu Nov 19, 2020 3:24 pm I offer vapor blasting services. sad now ever back yard low dollar people are offering this service. we offer the service 2 ways, you clean the internal parts or we can offer this service. I always thought the engine builder was to inspect and check all passages.. as far as pistons we tape the skirts and do the ring lands and piston domes.. sbc

Good one Charlie, You had me going there for a while but now I realize that you were just yanking our chains.. Because nobody, but nobody blasts ring grooves, ring lands and dumps anything but oil in drainback holes and wrist pin oiler holes.
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Re: Is it a good idea to vapor blast pistons, OHC alloy cam tunnels/journals ?

Post by bentvalves »

I believe I was advised with old boat anchor junk domestic iron crap you can lightly dust the skirts with glass, clean well, and rub with a wristpin to plateau it. It will hold oil well with this surface finish, if it's too rough its going to beat the crap out of your cylinder wall.
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