Soda blasting engine case - Page 2

KTL · 04-30-2012, 07:10 PM

Yep Andy is right on and picked the perfect topics to link. You want to make sure the spray bar is oriented so that the single pin holes are pointing out/up toward the valve covers and the double pin holes are pointing down into the cam housing.

The other check is to ensure you have the big holes in the spray bar (cam bearing oiling holes) aligned with ALL the cam bearing bore holes. Take a look at this picture.

The cam oiling holes at the ends of the spraybar are indeed lined up with the threaded holes in the cam housing at the outer cam bearing bores where you have a threaded plug w/pilot pin at one end and the cam oil line supply fitting at the other end. But the inner spraybar cam bearing oiling holes ARE NOT lined up with the holes in the middle two cam bearing bores.

The key is to align the big oiling holes in the spray bar with the plugs on the exterior of the cam housing as pictured by Jim Williams in the second link

But Jim's statement that says "Note the holes in the tube, and the chain (correction- should say "cam") housing plugs. The plugs cover the hole which was drilled in the housing to get oil to the cam journals. If the spray bar holes are aligned with the housing plugs and the end hole in the bar is facing outward, there is only one way the bar will fit properly." is incorrect. You can have all of the large spraybar cam oiling holes properly aligned with the holes within the cam housing and still have the pin holes 180 degrees out of alignment. So remember the rule, one pinhole points up/out, two pinholes point down/in.

You can replace the plugs with the factory aluminum plugs. They are part number 901.105.379.00 Or you can tap the hole with a 1/8" NPT tap and install threaded plugs. Then the future janitor of the spraybars can remove them a lot easier!

KTL · 04-30-2012, 07:19 PM

Quote:

Originally Posted by KTL

Also be careful to not drill too far when you go thru the plug. If you break thru and your momentum carries you to the next place the drill bottoms, you're hitting the spray bar itself. There's ample room between the end of the plug and the end of the spray bar. It's a decent sized cavity. So when you're nearing the end of the plug, go slow with no pressure on the drill. Then when you break thru, you don't jump down on the end of the spray bar.

I take back what I said here. The distance between the spraybar end plugs and the spraybar itself is very small. After looking at my towers again to respond to some questions, I would not recommend drilling all the way through the plug. Stop short of going thru the plug!

Lastly, you want to use the threaded fitting with the pilot pin to align the spraybars BEFORE you install the aluminum plugs. Doing so establishes the proper lateral location/depth of the spraybar in the housing. Then you can tap in the aluminum plugs. I suggest doing the pilot pin fitting install first, to avoid moving the spraybar when you're tapping in the aluminum plugs

brp914 · 04-30-2012, 07:24 PM

thanks!

TT Oversteer · 07-10-2012, 11:16 PM

Ok it's been a while since I started this thread but I finally blasted the case. I was a bit turned off by the mess created by my first attempt at soda blasting my cam housings but I made a simple cardboard "blast cabinet" and added a tarp to collect the overflow which made cleanup very easy. I taped off the oil galleys with electrical tape to prevent the soda from contaminating the passages. The soda blasting easily cleaned the old sealant and gasket material from the mating surfaces and spigots where the cylinders mount up to the case. The soda is so gentle that it cleans easily without removing any aluminum material. When done, I washed the case halves with soapy water and rinsed thoroughly, then blew dry with compressed air. I also flushed the oil galleys and piston squirters several times with brake cleaner and compressed air. There has been some concern here about the soda clogging or contaminating the oil passages but, honestly, I don't see this as a problem with this method. Any residual soda is such a fine powder that it simply blows clear with a shot of compressed air and dissolves completely with water leaving the case completely clean and free of contaminants. Here's a few pics of the finished product. I'm very happy with the results and the case is now perfectly clean and ready for assembly.

tom1394racing · 07-11-2012, 12:58 PM

The concern with soda is if it mixes with residual oil, it can create a sludge that will not easily rinse. It is important to make sure all oil passages have been thoroughly cleaned before soda blasting.

917guy · 917guy's Garage

I am getting into this string long after everyone has moved on... Oh well.

I have been grit blasting Porsches and their parts since the 1960s. I used to just wear a mask etc. For about 30 years, I have been using a mattress bag. This is way better. I poke a hole for each of my hands in the 2 corners opposite to the end which was cut to remove the OEM product. The bags I use are about 6 mil thick polyethylene. With delicate work, I use bare hands. I use heavy rubber gloves on my hands, then pushed through the holes, for heavy blasting. If you do not like the transparency of the poly, you can cut a 3 by 6" hole, and tape over a window made from a piece of clear shelf-pack PVC. The view through the poly is not bad in bright sunshine. In this way, you breathe the air you trapped in the bag before you started making dust. No sand drops out off your eyebrows a day later into your eyes.

I like to blast on nearly windless days. A few MPH is good, as it clears the dust. I walk a few yards away before taking off my 'hood'. I use tarp curtains to keep the dust and grit from getting too far away. I sweep up and re-use. When the grit turns to 10 micron dust, it blows away.

I used to blast small parts like Zenith carb housings with very fine glass beads. Of course you need to plug openings or remove OEM plugs.

I sandblast whole engines, after removing the flywheel, greasiness, shroud, exhaust and intake. A rubber lab stopper goes in each intake and exh port. Rags and duct tape and duct seal putty keep sand out as needed. It removes grime and oxidation, and little gets inside. This is all written up in earlier issues of my RED RIVER SPORTS CAR ENTHUSIAST newsletter.