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After living with a noisy exhaust manifold on my 1989 SPG through most of last summer i finally got around to doing something about it this week. Turns out there were two broken exhaust studs.
There was a lot of helpful (but scattered) information on this board that pointed me in the right direction but i thought i would write a little summary that would put it all in one place.
Here's what i did:
First you need to detach the downpipe from the exhaust elbow and then remove the exhaust elbow itself. I didn't have a problem with these nuts but the air ratchet certainly helped getting into some tight spots. Once these two items are off you need to loosen the supporting bracket (one bolt) in order to swivel it out of the way. This should give you just enough clearance to remove the exhaust manifold once you have undone the 7 nuts that hold it to the head. Again, a small air ratchet really helps with this.
Once the manifold is off you will be able to see the broken studs. I had two: one at the front of the engine (cylinder 1) near the motor mount and one at the back near cylinder 4. They were both broken off perhaps 1/8" below the surface of the head.
I ended up using a dremel tool with the right angle attachment and tungsten carbide cutting heads (also by dremel). I tried regular drill bits but made little or no progress (beyond breaking 7 or 8 bits). The tungsten carbide cutting heads are expensive but they work quickly and are fairly easy to control. Using a small dental mirror to check my progress (and make sure i was as close to the centre of the broken stud as possible) i drilled/ground into the studs to approx. 1/4" of depth.
Note that i did not bother to center punch the stud before i starting drilling. Although i would certainly recommend it i couldn't get enough clearance to swing a hammer at the punch particularly near cylinder 1. I should also note that the right angle dremel attachment allowed good access to the stud at cylinder 1 adjacent to the motor mount (ie. i didn't have to remove or loosen the mount).
The tungsten carbide bits i used produced a hole that was approx. 1/8" in diameter. This allowed me to use #2 screw/bolt extractors (from home depot). I prefer the square fluted ones rather than the screw type extractors. The fluted ones allow you to pound them in and have a beefier profile that (i feel) prevents them from snapping. I ended up shortening the extractor by grinding the (non-business) end down perhaps 3/4" to allow more clearance to tap them into place.
Once the extractor was firmly seated in the top of the stud I used a t-handle (cylinder 4) and a pair of locking pliers (cylinder 1 where i didn't have enough room for the handle) to twist the broken studs out.
Although this technique sounds easy enough it took me a couple of frustrating days to work it out. Assuming you have the exhaust manifold off the head this technique should allow you to extract a broken stud in about 30 minutes or less.
posted by 24.84.2...
, Thu, 27 Mar 2008 12:07:23
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