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I have ordered a new stock head pipe for by GT 1.9 from Opel GT Source and am having some concern on how best to proceed with removal of the old pipe. Looks like the front bolts at the head can be removed from the bottom, but the rear bolts may be a problem. Would it be easier to get to them by removing the carb and going down from the top of the engine? I assume that most if not all the bolts will break off and have to be drilled out. Any tips will be greatly appreciated.

Wayne
 

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Detritus Maximus
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3,524 Posts
All from the bottom. Need a good quality 6 point socket, 18" extension and a flex adapter.
Plenty of PB Blaster and soaking for a couple days.

The alternative is to remove the carb and cut the existing headline and remove the intake/exhaust assembly. This allows you to heat the bolt area with a torch to help get the bolts to release.
I like to install studs and use brass nuts for reinstallation.
 

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Opeler
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1,599 Posts
I have ordered a new stock head pipe for by GT 1.9 from Opel GT Source and am having some concern on how best to proceed with removal of the old pipe. Looks like the front bolts at the head can be removed from the bottom, but the rear bolts may be a problem. Would it be easier to get to them by removing the carb and going down from the top of the engine? I assume that most if not all the bolts will break off and have to be drilled out. Any tips will be greatly appreciated.

Wayne
If I remember correctly, the head pipe nuts are made of copper and may not be as badly seized as you might expect with carbon steel nuts. If the pipe has been changed several times in its life, then the nuts may no longer be copper.

I think that I got all of mine off from the bottom, but it's been a long time since I last did that.
 

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Just Some Dude in Jersey
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16,258 Posts
I don't think they are copper.

One thing to keep in mind is that the intake and exhaust being on the same side of the engine and sharing those six manifold-to-head bolts caused an annoying compromise that haunts all of us Opelers to this day: The bolts have to be UNDER-tightened compared to other bolts of a similar size. About 10-15lbs under-tightened. This is because of the heat expansion of the exhaust manifold compared to the lack of expansion of the much cooler intake manifold. The exhaust gets glowing red hot, even under casual driving, and they're in virtual contact with the intake manifold, which has ambient temp air passing through it. If you actually tightened those bolts to the torque that would prevent them from slowly unscrewing over time, the disparity of intake/exhaust expansion would cause the bolt heads to snap off. This is one big reason that vacuum leaks are the #1 reason our engines won't start one day, even though they ran fine the day before. When this happens, usually just 1/4 of a turn of those bolts fixes the problem and the car is good as new. A lot of "barn find" GT's often have the strangely similar odometer reading of 70,000 miles on them. You end up wondering why a perfectly okay GT was parked in a barn. And you'll often find a whole bunch of monkeying around in the engine compartment as the PO searched for the problem. This problem was not common knowledge. Experienced Opelers learned to recognize the symptoms and when the car would become hard to start or wouldn't run at less than 2500rpm, they'd grab their special assortment of 15mm wrenches and sockets and tweak those bolts. Problem solved. It's not a bad idea to slather those bolts with red Loktite when putting them in and it's also a good idea to install brand new bolts, because that looseness would round off the sharp points of the bolt threads and cause them to frequently come loose. OGTS sells allen head replacement bolts. Most of us have created all sorts of "special tools" for those bolts: multiple combinations of sockets/extenders/u-joints/ground down wrenches for the manifold bolts, short stubby screw drivers for carb adjustment, and tools for tightening the valve cover bolts under the cowling.


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The Young One
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To get the socket up there you definitely need a flex adapter. I think I could get to 3 of the nuts with no flex adapter but the other 3 are impossible if you don’t have one. I was taking mine off because I was putting a header on so I just broke all 6 studs. To get them not to break they will have to soak in penetrating oil for a long time. Also jack up the front of the car and put some big block of wood or jack stands so you can work underneath the car.

Sam
 

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Detritus Maximus
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3,524 Posts
If I remember correctly, the head pipe nuts are made of copper and may not be as badly seized as you might expect with carbon steel nuts. If the pipe has been changed several times in its life, then the nuts may no longer be copper.

I think that I got all of mine off from the bottom, but it's been a long time since I last did that.
Could have been copper plated bolts. I've seen that before as a form of antiseize.
 

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Opeler
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260 Posts
Now would be a good time to install the shorty header from OGTS at the same time. Then it wouldn't matter if you broke a bolt. You could kill two birds with one stone. By getting rid of the cast exhaust manifold it will help remove the heat that raised hell with your carburetor when you tried to start the engine when it was warm. The only problem had was starting the two bolts near the motor support. So I put a block of wood on my floor jack to lifted the engine a bit by lifting it under the oil pan. Then I removed the motor mount which gave all kinds of room.
 
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