Engine repair/threaded camshaft plugs

Dharn55 · 07-03-2009, 05:45 PM #1

Another update on the saga on my intermix problem and the repair of the engine. Those of you who have been following it will remember that I had an expansion plug blow out of the end of a camshaft and have been struggling with that problem. Finally sent the cams out to have the ends drilled, threaded and plugged.

Here are pictures of the camshafts. The first shows four intake cams, on the left is a cam with the expansion plug in place, the next shows a cam with the expansion plug blown out, the next is a cam that has been drilled and threaded, and finally a cam with the Hex plug installed.

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Dharn55 · 07-03-2009, 05:46 PM #2

Here is a close-up of the cam with the expansion plug in place. In this case the plug has not been “deformed” by my home made tool.

Dharn55 · 07-03-2009, 05:47 PM #3

Here is a picture of my home hade tool. The tool fits in the end of the cam to hold down the cam when the cam cover is removed. The manuals give specific instructions on the depth/setting of the bolts that fit into the end of the cams. I did not think this was critical, not even being aware of the expansion plugs, so I screwed my bolts pretty far in, pressing against the expansion plugs. I believe this was a major mistake.

Dharn55 · 07-03-2009, 05:48 PM #4

Here is a picture of the tool inserted in the end of the cam with the plug in place. The hex driver bolt I used is actually small enough to fit inside the expansion plug. I think it should be a larger size head, so it fits into the end of the cam, but not into the expansion cap, However there is not much room beyond the expansion cap. I have not seen the factory tool to see the size of the bolt heads on it.

Dharn55 · 07-03-2009, 05:49 PM #5

Here is a close-up of a cam with the expansion plug blown out. Notice the shoulder inside the cam where the diameter of the hole gets smaller. It is only about .2-.2.5” inside the chamfer on the end of the cam.

Dharn55 · 07-03-2009, 05:50 PM #6

Here is a picture of the expansion plug that came out, and the cam cover plug. Notice how shallow the expansion pug is, only about 1.8” deep. This cap is pressed into the end of the cam, and the widest part is the top/hollow end, so it needs to go all the way into the end of the cam so that the widest part is beyond the chamfer. You don’t want to reuse an expansion cap as they are pressure/interference fit, and once they lose their shape/diameter reuse is very dangerous. All the domestically available expansion caps I found (from Dorman and other) were 2.5+” deep, so that the widest part would not be far enough in the properly fit, this is because of the shoulder inside the cam. And Porsche will not sell just an expansion cap.

Dharn55 · 07-03-2009, 05:51 PM #7

Here is a close-up of the cam with the end drilled and threaded. Notice the hole in the bearing area. This feeds oil to the bearing/journal at the end of the cam, so it is critical that the hex plug not interfere with this hole/oil flow. So the depth of the hex plug is critical

Dharn55 · 07-03-2009, 05:52 PM #8

Here is a picture of the hex plugs. The machine shop used standard, easily available plugs and shortened them so that they would not interfere with the oil passage.

Dharn55 · 07-03-2009, 05:53 PM #9

Here is a close-up of the cam with the hex plug installed. Notice the Red Threadblocker used to secure the hex plug in the end of the cam. I am going to modify my home made tool so that it will fit into the hex of the plug to hold the cams. I am not really worried about it pressing against the hex plugs, with the thread and threadblocker it is not coming out.

Dharn55 · 07-03-2009, 05:54 PM #10

Here are a couple of pictures of the other ends on the intake cams with threads and plugs

Mother · 07-03-2009, 08:10 PM #11

Great job dont think those are going to move any. So you had to tap the cams for the plugs?

Dharn55 · 07-03-2009, 09:23 PM #12

Took them to a machine shop and had it done. The cams are extremely hard metal and I did not want to take the chance of doing it with my home tools.

zdr2k · 07-04-2009, 01:21 PM #13

dang dude. great writeup. i would never attempt something like this!

RSstop · 08-21-2010, 07:59 AM #14

Thanks for the inspiration and letting us learn from your trails.
Could you PM or post the dimensions of your hold down tool in #3 above? I am trying to make one today so I can replace my variocam solenoid.
I tried a PM but I need 15 posts before I can use PM.

Doug996InKC · 08-21-2010, 11:03 PM #15

Nice work. Is the hex plug made of brass? What modifications do you recommend making to your homemade cam-holding tool?

Engine repair/threaded camshaft plugs

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