I'm ready to take my motor to the blaster. Have a few questions.
Do i need to mask bearing surfaces
Plug threaded holes
Is vapor blasting ok for parts that will be painted
1. No, just remove all bearings, moving parts etc. RPM cable stuff etc.
2. I would.
3. Yes. Vapor blasting only cleans and lightly polishes.
1 — no
2 — I've not had problems with vapor honing threaded parts. I have done plenty.
3 — make sure you don't vapor hone with glass bead before you paint. You want your media to cut, not polish.
If your painting don't waste the money vapor blasting. Case work on the other hand will turn out better than factory.
Thanks guys.
Took 2 sets of engine cases. 1 set of engine side covers and 1 set of barrels and heads. $275 and i'll have the top end by sat. to send out for new bore and pistons.
Dry blasted surface will hold on to paint better than wet blasted.
Yep. Only the cases are gettin vapor blasted.
Parts came out real nice. Top end is off to machinist for the works, bore to 2nd over, mild porting and head o-ringed and squish correction.
So time to paint the engine covers. What's the best process? Mask, polish then mask and paint. Or mask, paint then polish?
I've tried a couple ways on the cylinders/fin edges. The best result was after spraying lightly use acetone until clean. The quickest was using a dreamer with a fine grinding wheel.
Quote from: lawnboy on June 03, 2021, 07:31:44 PM
Parts came out real nice. Top end is off to machinist for the works, bore to 2nd over, mild porting and head o-ringed and squish correction.
So time to paint the engine covers. What's the best process? Mask, polish then mask and paint. Or mask, paint then polish?
I have had the best luck with mask, polish then mask, paint.
Dry blasting was mentioned above; do I dare to try and lightly sandblast a set of cases prior to painting, or is it too aggressive? Maybe not necessary?
#80 glass beads. Sand is far too aggressive. I do glass bead work as a side business if you are interested.
Tim, my first instinct here is a hay joke, but I'm putting that aside (for now). I have a portable HF blaster that my lovely wife snagged at a yard sale for the princely sum of $5 and I haven't even tried it out. Should I buy some beads for surface prep with this thing, or go chemical or what? Mr. Ritter did my top end and Mr. Garland has my crankshaft, but another package to the other side of the continent? Hmmm.
Let me add a precaution for both sand and glass beads. They both shatter on impact and create a very fine dust that can cause silicosis and can lacerate nasal and lung tissues causing pneumonia and nasal/upper respiratory infections. If using a sealed system (blasting cabinet), it must run under net negative pressure and the airborne dust must be settled or filtered out before opening to add/remove parts. Aluminum oxide grit does not have this problem, but is more aggressive and leaves a bit different finish. Aluminum oxide is often preferred before painting as it gives a better "grip". Glass bead is usually preferred for surfaces that will not be painted. Sand really should not be used and silica sand is barred in my experience. There are several aluminum oxides such as garnet that are slightly softer and produce a bit softer finish. And, for very cheap media there is coal ash that can strip paint, but leaves a lot of carbon residue as well as producing some silica issues. We had a blast booth at both of the labs that I have worked and both started with glass bead. Both changed to aluminum oxide due to health issues (actually banned at the first government-owned lab) and media longevity (glass beads turn to dust and have short reuse life, aluminum oxide lasts much longer and cuts faster).
Yikes, thanks for the warning. I'll find something else to do with the sand!
Yep breathing the dust is not good for sure. I have a small commercial machine that does a good job and a lot of experience.
I found this information helpful:
https://pittsburghsprayequip.com/blogs/pittsburgh-spray-equipment-company/how-to-soda-blast-in-a-regular-sandblaster-a-complete-guide (https://pittsburghsprayequip.com/blogs/pittsburgh-spray-equipment-company/how-to-soda-blast-in-a-regular-sandblaster-a-complete-guide)
I've built my own vapor blaster and designed nozzles for the guns used. My top end looks great after doing a new rounds of blasting.
I typically vapor hone aluminum parts with a mixed blend of glass bead 170 - 325 mesh. For parts I intend to clear coat, I add 140 mesh aluminum oxide to the mix. Glass bead vapor honing isn't good for painted parts, as it polishes the surfaces and lacks the bite needed to bind durable paint coatings to the aluminum. That's not to say it won't work, but that you run a much higher risk of your paint peeling or chipping months or years later. Dry or wet blasting doesn't make much of a difference as far as paint is concerned, since the water is really just a vehicle for the blasting medium and serves to knock down dust and clean as it blasts. You absolutely can vapor hone machined surfaces, but do not do it with anything but glass bead as your blasting medium. Aluminum oxide and silicon carbide will remove material and have an effect on tolerances. On high tolerance parts, or parts where movement and oil is necessary, I highly recommend hitting all parts with compressed air in every hole, cavity, thread, etc. Follow it up with a rinse, then blow it with compressed air again. If there is glass bead left in a threaded hole, there is a huge risk of that glass bead become a thread lock like you've never experienced before. If you get glass bead in a bearing or rotating part, you might as well consider them together for life. The bead gets into places you never though possible. When I vapor hone heads, I always follow up with a valve grind/polish. I don't for journals, and so far I've never had an issue.
:good: thanks for the excellent information :like: