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Mateingfaces between cylinder and head 3,2 engine
I am undertaking a full rebuild on my 3,2 engine. I find it peculiar that there is no head gasket between the cylinder top and the head. But I belive the Porsche engineers found god enough.
My problem is that I have had a little leak between the cylinder and the cylinder head. After I have cleaned my cylinders and cylinder heads I can see at some plases some small wounds in the matingfaces. I guess that I have to bring the parts to a mashineshop for levelling. I got this idea that I should place a gasket between the cylinder and cylinderhead, e.g. a glowed copper ring placed in a groove machined in the cylinder upper matingface. My cylinders and pistons are made by Mahle. Anybody who has experience with both levelling and installing head gasket on a 3,2 engine. |
There is no need for head gaskets. Have your heads and cylinders resurfaced and install Supertec Heads stud kit and your problem will be solved.
We can resurface your heads and cylinders. |
As usual, Henry has given good advice. You may have to compensate for the materinal removed from the heads with a thicker base gasket.
Jeff |
Thanks both of you.
As I live in Trondheim, Norway there is not any machine shop that has much experience with resurfacing on Porsche engines. I will take them to a machine shop where I can watch the process. I am aware of that you must remove the same amount on each side. I am also aware of that there is copper gaskets of both 0,5 og 0,25 mm thickness. I guess that the standard ones are 0,25 mm. That leaves me with maksimum 0,25 mm to remove. Anyone who has an anvice how to set up the head and cylinder when performing the resurfacing? For the heads I guess one way is to remove the studs that connects the head to the camshaft housing and clamp it down. Will that work or is there a better way? I am not sure how to do it with the cylinder. Maybe make a "dummy" case and place the cylinder in it and then clamp it down to the desk. I hope you understand what I mean. I am lost for the right expressions in english. |
On mine, the shop removed about .19mm. You can also stack a couple of gaskets if you need more clearance.
Jeff |
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Thanks for your photos Henry. I am not sure that I understand how to perform these thasks.
I am not sure how to install the heads to the lathe. As Henry showes on the photo there is the mathingface between the head and camshaft housing that is been machined here. I am going to resurface the mathingface between the head and cylinder. I guess that it will be difficult to mount the head in exact center if I am going to use a lathe. Is it not easyer to use a mill to perform that task? Do you have a picture of the setup when resurfacing the mathingface on the face that meets the top of the cylinder? Likevise I do not understand the setup for the cylinder. I understand that the cylinder is put on to the tool and clampt down with the cover. But I guss you then will cover the inner part of the mathingface that will meet the head. Do you have a picture that shows the cylinder installed? I understand that it is possible to use the tools fabricated to resurface the bottom end of the cylinder. Am I missing something here? I am appreciating all advices. |
here's my rig. it's a copy i made from the factory tool. the head bolts up to the tool in the chuck, and the disc in my hand centers in the tailstock spindle which is moved up to the head and slips into the counterbore for the cylinder for centering purposes before the head is fully tightened to the tool.
http://forums.pelicanparts.com/uploa...1088036083.jpg |
henry, how do you true the top of the cylinder in that setup? the tool appears to overlap the top surface to clamp it tight.
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The picture has the wrong cap. The cap for this repair has a taper where it fits in the cylinder. We also use a full sleve incert that supports the cylinders full length. |
If you use a taper that fits into the top of the cylinder, and then tighten it down so the taper acts as a wedge to hold the cylinder, then won't this spread out the top of the bore and tip the mating surface outwards?We have found that The aluminum cylinders are pretty flexible.
Using an aluminum biscut to fit into the step in the head for centering purposes may not ensure a concentric cut. Most of the heads I have done have that step oval by a number of thousanths, they seem to have a temdencey to warp outwards on the hotter side of the head. Do not limit yourself to using one peice of equipment to do a particular job, a mill can be used to resurface the heads and can be repeatable within tenths and offers more control for the operation. |
Here is an example of a head resurfaced on a mill. These were done special with a groove incorparated for a sealing ring, so if you are wondering why there is a break in the center of the mating surface that is why.
http://forums.pelicanparts.com/uploa...1089844324.jpg |
the aluminum biscuit simplifies the centering of the head, and the head still may need to be tapped to one side or the other to nicely center it. the outer step in the head isn't particularly important anyway, so if it's out a couple of thou, so what.
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I have found that area to be very critical in sealing and posistioning of the cylinder barrel. Like I mentioned, this head was machined for a sealing ring, so it is absolutely imperative to get the head concentric, otherwise, the ring grooves will not match up. I have always dialed in the heads to get them centered before cutting them.
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Back to the original question, the factory did use a head gasket on the C2 turbos. I would guess for a better seal. I have also seen the C2 gaskets used on high compression engines, and I used them on my 3.4 turbo rebuild. (3.3 turbo upgraded with RUF 3.4 p & c) It is probably a better answer than the O-ring that Porsche abandoned inthe late 70's.
But these are high compression or turbo engines. A basically stock 3.2 does not need these mods. |
Tor,
Whoa, whoa, whoa. Before you go jumping off the deep end, call Ollies's Automotive in California 714 558-7334 and talk to Ike. They are perhaps one of the best kept secrets around. For years, they have been doing much of the machine work for ANDIAL and Porsche Motorsports North America. That means their work has gone to and won every major race in America as well as Le Mans. They will tell you the right way, you do it how you want. Good Luck Glenn Yee Motorsports, LLC |
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This set of twin plug, polished chamber heads were properly machined as per Porsche factory on a lathe not a mill. Although we have a quality mill, it is our understanding that the lathe process is for more accurate.
http://forums.pelicanparts.com/uploa...1090000325.jpg |
When you use a mill and cut this surface the cutter corner will aways be cutting across the surface you are trying to use as a sealing surface. Any small scratch or cutter mark creates a potential ditch from the combustion area to the outside. I am not saying it can not be done I just believe that you have a larger window for successful sealing when you cut this surface with a lathe and the cutter marks are less likely to cross the sealing area.
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Very good thread. Smart guys weighing in.
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Why hasn't anyone used the term "fly-cut"?
Regards, |
A fly cutter is in effect just a large diameter single point face mill designed primarily for cutting across flat surfaces. Because of the counterbore of the sealing surface of 911 heads it is no more suited for this application than a smaller end mill.
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Tor,
I had the same problem a few years ago on my 3.2. I decided to have a groove cut into the tops of the cylinders like on the 3.0 engines and use a CE ring. It worked like a champ. Ted Robinson did this for me at German Precision. I suspect you could have it done at a machine shop if you can get the dimensions of the groove from an SC cylinder. The other thing you really should do is replace the lower studs with steel studs. This will help the clamping force and eliminate the chance of a broken head stud. -Andy |
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