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Analysis of the valve using X-ray fluorescence shows that it is primarily Inconel, 73% Nickel, 19% Chromium, 2% Titanium 1.5% aluminum (could be surface contaminant) 1.5% iron...... Looking closely at the new valve OSI930 sent me shows evidence of a weld line at the seat area, I suspect its Stellite welded but will wait for test results. The new guide looks very much like copper, and I suspect its beryllium copper, but have not tested it yet. I work slow but results are worth the wait.
David
Old 06-07-2017, 06:31 PM
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I said primarily Inconel because the threaded section at the top is a different alloy and is magnetic, as its common for exhaust valves to be magnetic on the stem I did not bother to test this area, I suspect it was cheaper to weld on another material and thread that rather than try to cut threads in Inconel (it is a ***** to machine) The stem is nicely finished, and hard chrome plated to resist wear. The high73% nickel and 2% titanium indicates this is Inconel X750, the same material used in rocket combustion chambers, think Saturn V!!!! It does not get much better than that. Unless you weld a layer of Stellite on top!
David
Old 06-07-2017, 06:38 PM
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Does any one know where to get the two(2) flat washers that go on both ends of the wastage spring? Mine were disintegrated

If not available, what are the dimensions

Inside diameter (I.D.)
Outside Diameter (O.D.)
Thickness (t)

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Old 06-08-2017, 07:19 AM
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OD 2.745
ID 2.215
Thickness .021
Old 06-09-2017, 03:53 AM
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Thanks for the information, I guess they are no longer available? What material should I use? Stainless Steel?
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Old 06-09-2017, 04:17 AM
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These appear to be Cadmium plated, but I believe stainless would be fine, I am checking with a local shop with a laser cutter, I am planning on making a coupe dozen.
Old 06-09-2017, 05:06 AM
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Originally Posted by reclino View Post
Analysis of the valve using X-ray fluorescence shows that it is primarily Inconel, 73% Nickel, 19% Chromium, 2% Titanium 1.5% aluminum (could be surface contaminant) 1.5% iron...... Looking closely at the new valve OSI930 sent me shows evidence of a weld line at the seat area, I suspect its Stellite welded but will wait for test results. The new guide looks very much like copper, and I suspect its beryllium copper, but have not tested it yet. I work slow but results are worth the wait.
David
David,

Have you measured the new part yet? What is the actual valve clearance?

Thanks,
Dave
Old 06-13-2017, 06:14 AM
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I have measured it a few times and handed it to a tool and die maker friend to double check my numbers. The new guide ID measures .3978 at the top and .3980 at the bottom. Inside is mirror honed finish. The new valve OD measures between .3904 and .3903, my used valve measures the same.
David
Old 06-13-2017, 04:58 PM
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The guide in my used wastegate measures .3982-.3990 I am really surprised by these numbers, but it matches the way they feel, slightly loose. I suspect Porsche built these on the loose side, as the air lost really is minimal but it is cooling the valve stem and guide interface. A tighter guide could be made, and for a street car it would probably be just fine. On a high HP race car like a 935 I suspect it could lead to a seized valve which might grenade the engine.
David
Old 06-13-2017, 05:18 PM
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Thought experiment for the day. Things get larger when they get hot. CTE of Inconel X750 is 8.1x10(-6) or .0000081 at 1200 deg F. See attached picture of my calculations. I will guess temp of the housing and do a calculation for it but let's say this is worst case, cold engine to full tilt boogie. So the valve is allowed to get hot and expand. At 1200 deg, the valve expands .0036 inch. So the clearance can drop alot when hot. If you build a new guide and make it tight like in a cylinder head you may end up with scuffing and wear with the guide or worst case a stuck wastegate.
Old 06-26-2017, 06:57 AM
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Has anyone made some replacement valve guides I could buy?

My machine shop wouldn't touch it.

Thanks,
Dave
Old 08-04-2017, 11:52 PM
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I have contacted a shop about making valve guides. Material will be a berilium copper replacement, it's material properties match or exceed the original. I am also waiting on quotes for the shims that go top and bottom on the spring and a gasket that goes between the top aluminum and cast iron base. I would be able to offer all together as a kit to rebuild the 930 wastegate. Anyone interested?
The only unknown is what dimension to spec for the ID of the guide. I would feel safe building the guides .005 clearance, but the NOS guide and valve provide .008.
Anyone care to chime in?
Old 08-10-2017, 04:56 PM
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I'll take one.

Why not just go .005 and if someone wants a little more they can ream it out themselves?
Old 08-10-2017, 06:52 PM
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David,

It is good that you found a shop that will machine beryllium copper. I assume the shop knows the hazards involved with machining this material. When I worked at a naval shipyard, the engineering department had to provide special instructions so the machinist were not exposed to its vapors or dust.
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Old 08-11-2017, 08:25 AM
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Read what I posted again, material will be berillium copper REPLACEMENT. It will be made of a precipitate hardened copper nickle silicone alloy. There is no need to use berillium copper for this type part anymore. Trying to hone one yourself to fit would be toxic.
David
Old 08-11-2017, 12:08 PM
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I have price quotes in on a small run of wastegate valve guides. I have also got a quote in on washers for the spring. To get gaskets made for between the cast iron base and aluminum top hat I need a couple of dimensions. Has anyone got a wastegate all the way part that could measure a few things?
Old 09-08-2017, 04:28 AM
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I have a found metal stamping company who will do a small run of these shim washers. I am doing them out of stainless steel and plan on coating with moly dry film lube Sandstrom 28A. The cost each washer is going to be $7.25. so $14.50 plus shipping. Will be about 2 weeks before I have the washers in hand.
David
Old 09-12-2017, 10:04 AM
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By November I will have valve guides available for $43.50 each. Will also have gaskets available for between hot and cold side of wastegate for $17.00 each. That with the shims at 14.50 for 2 will make a kit cost of $75.00 for all common wear parts for the wastegate.(except the Diaphragm) Can anyone interested in a kit PM me so I have some idea demand. I am diverting money I had saved for cylinder head rebuild to this effort.
David

Last edited by reclino; 09-15-2017 at 05:22 AM..
Old 09-15-2017, 04:18 AM
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