Intermix repair/Camshafts/Threaded plugs

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.

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

Here is a picture of my home made 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.

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.

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.

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.

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.

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.

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.

Here are a couple of pictures of the other ends on the intake cams with. I have had both ends of all four cams drilled and threaded, and am putting hex plugs in all of them. I thought I would be putting the engine back together this weekend, I ordered the last few parts needed and they were supposed to be overnighted to arrive yesterday or today. Found out this morning that Sunset had mistakenly sent them by ground, so i won't have them until next Wednesday or Thursday, very frustrated, the parts were not available at the local dealer. Found them in stock at a CA dealer, but neither FedEx or UPS is delivering on the 4th. So now I am just sitting and waiting.

Wow, now it all makes sense. Great pics to explain everything. Hopefully it will all be back together soon.

Very good pictorial.. This is exactly the way that I do the procedure. You can modify your cam holder to incorporate an 8mm hex wrench so it will lock into the threaded plugs very tightly. In my tool they are allowed to rotate so the cams are held tightly, but the plugs are not damaged. Impressive!!! Hopefully in the future we can make this not quite so painful for others to do what you have done.. It just takes time.

This will definitely be very useful for someone in the future. Thanks for taking the time to post pictures and the explanation.

Best technical pics ever for this forum. Very informative.

Yes - I'm impressed - but I have to admit I'm not following the plot so well. Maybe I'm overthinking it. Replacing the expansion plugs with the hex plugs I get, although I'm not clear if you buggered up the expansion plugs so that's why you're replacing them, or if you are replacing them as an "upgrade". My real question is.....why the big todo with the cam holder tool. What is it's purpose? Kudos for pushing the DIY envelope though mate.

Jasper: You need to read his other posts about his intermix problem/head repair and then cam expansion plug damage and blow out after engine rebuild and reinstall.He's documenting this saga and giving great detal to his problems with detailed photos.

Quotes source post: 6703256

The factory tool for the 996 uses a regular hex head 8mm bolt. The head of the bolt will not press into the camshaft end enough to damage the sealing cap. In the case of the Boxster (or at least some Boxsters) the bolts in the tool are replaced with socket head cap screws like the ones you show in the tool in your picture.

<clapping> nicely done - these are awesome threads!

Thought i should mention that with these mods the two factory tools, 9634, which is the cam hold down tool I made, and 9612, which is the cam alighment tool, will no longer fit without modification. By the way, Doug Dornbush make a much prettier tool than i did as you can see from this picture. And note that his tools uses hex head bolts that should not go into the expansion bolts. I thought I was being clever using the round headed hex driver bolts, not so!

Excellent info Dharn55. I am suffering same intermix failure as you. Will be attempting similar repair. Engine should be coming out this weekend if I get time. I am closely following your saga, and believe me I am a #1 fan! Tim S

sehorntx - Let me know if there is anything I can do to help. I have developed somewhat of an expertise on this. Once you drop the engine pull out the sparkplug tubes, start on 1-3, actually #1. Now that you know what to look for you should able to see the crack (assuming it is the same crack/area) without removing the cam cover. Here are some pictures of the crack again. You can see where it runs down the sparkplug chase. This is the part that you should be able to see with the cam cover on. The rest of the crack is not visible until you pull off the cam cover, cams and the tappet holder.

Darhn - is that plug just to the left of your finger an issue at all or anywhere else on the engine? Seems like this engine has a lot of 'plugs'???

That is an expansion plug. I am not sure if it is an oil passage or a coolant passage. therer are lots of thee plugs in the head and block. You see them in most engines. Two purposes, one is to close off openings that were required in the manufacturing/casting process, the second is the concept of "freeze plugs." the idea of freeze plugs was to allow the plugs to give way before the block/head cracks when the coolant freezes. These used to be called welsh plugs. With modern coolants/antifreezes, freeze ups are much less common, but you still see these plugs in almost all engines. Jake Raby of Flat 6 says that when he builds engines he trys to replace as many of the plugs as possible with threaded plugs. It would be a big project and would require breaking down the entire engine. I am not too worried about these plugs, except at the cams. And quite frankly, if I had not pressed on the plugs in the end of the cams, one might never have come out. But the cams are a high pressure oil passage. Jake says he has seen quite a few of the cam plugs come out, refers to it as "mode of failure #11." another tech here on the site told me that he had never seen one come out, and he is very experienced. However, he also said he had not seen a cracked head until he checked a set he had and found the same basic crack that I had. I think a large percentage of the time when engines have failed the techs never really knew why, particularly when Porsche policy has always been not to tear down the engine, or to disclose the source of the problem. Most of the time when an engine fails, whether due to an IMS, intermix, cracked cylinder, etc. the engine is just repalced with the core sent back to Porsche. Of the local techs I talked to about my problem, none even knew there were plugs in the end of the cams. Someone like Jake Raby is specifcally involved in analyzing why engines have failed and how to prevent it in the future on engines they build. So their experience and perspective is alot different from a tech working at a dealership/shop. Almost everyone I talked to when I first had the intermix, techs and others said "new engine, no other option." And that was not the case, but was the standard approach, and encouraged by Porsche. And it is alot more profitable for Porsche to sell a new/reman engine for $14,000+, and to conceal the real problems, than to fix the engines (although what they really do is take them back to Germany and "reman" them, i.e. fix them and send them back out. Now that many of the cars are no longer covered by warranty, and Porsche has jacked up the price, particularly of the 3.4 (remember that 3-4 years ago a 3.4 reman was only about $8,000, and now they are $14,000+), and parts are available, more people are tearing down the engines, finding the source of the problems and fixing them.

Dharn55, I am with you brother right down in the trenches! Will lean on you quite a bit if you dont mind. While I'm a mere private in this army, you're the seasoned colonel! Will definitely be interested in the manufacture of special tools! Got the email specs for one tool already. Tim S

sehorntx - I was trying to send you a PM with some info, but it seems that you are not set up for one. If you send me one with your email i can send you some info.