Question about sandblasting the heads on my 1966 Type 3

[lakedawgs]

Hello,

Have not worked on my 1966 Squareback in a long time. Hopefully that is now changing with some work on the heads.

I have lightly cleaned with degreaser and rinsed w/ high pressure water at the carwash. They look pretty good to me so far.

I had a machinist buddy measure the valve guides and they are within tolerance on the ID. I have purchased new exhaust valves.

I want to sandblast the heads to better inspect for cracks. My plan was to reassemble the head rockers and springs with valves, to protect valve seats and guides, and blast away. I plan to reuse the intake valves. Will blasting hurt them? I plan to use 80 grit glass bead. Will figure out how to post pics and do so soon.

Thanks
Lakedawgs

[Marc]

The glass bead is insidious stuff, just having valves in the guides won't keep it from getting in.
Better IMO to leave the valves out and plug the guides (from both ends) with something like rubber vacuum caps stuffed into the ends - avoid blasting directly against them so as to not blow them out. Probably wise to screw some sparkplugs in, too...if you simply must blast the threads, be sure to clean them well afterwards.
You'll still need to do a thorough cleaning to dislodge the media which will embed itself into the surfaces of the rockerboxes, but at least there won't be any inside the guides.
I'm assuming that you plan to reface the valve seats (or at minimum, hand-lap the valves to the seats) before final assembly. The seats are hard enough that they won't be eroded significantly by glass-beading - but you still should minimize blasting directly at them if you don't intend to regrind them afterwards.

[lakedawgs]

Thanks Marc,

I figured leaving the valves in, with spring pressure, would help keep the sand out. I have read that you don't want to blast anywhere near the guides as they are bronze and the glass bead can get embedded in the bronze. Can't confirm as I have never blasted near bronze.

Yes, I planned on leaving the old plugs in for sure. And cleaning, I know will be a major job once done.
My plan, once done and clean, was to hand lap the valves/seats and then do a liquid test to see how the sealing is. If it just seeps lightly, I should be good, if more than that, I will get them done at a shop.

Have you used glass bead on heads before? Is 80 grit glass bead the way to go?

Thanks much,
Lakedawgs

[lakedawgs]

OK, blasted the heads, happy with the outcome. Torched the areas where cracks can appear, between the valves and plug holes, everything seems solid.
I am, however, going to go ahead and have the valve guides replaced and valve seats checked out. Valves were a bit 'cruchy' when I pulled them out due to glass bead. I have only used a blaster for general rust removal and as told, that stuff gets everywhere!! I forgot what a nasty job that is.
Will drop the heads at my machinist hopefully in the next couple of weeks.

THANKS
Lakedawgs