I just spent way too much time undoing a headpipe/exhaust manifold connection on a 240. I climbed under the car with a 15 mm 6-point socket, extension and breaker bar fully expecting to resurface within ten minutes.

Unlike the many other times I had done this task, the headpipe flange nuts were unyielding. Even using the blue flame wrench resulted in the royal pain-in-the-ass of two twisted off studs.

I was puzzled because I never had that problem before no matter how many rust belt winters a 240 had seen. Then it dawned on me - when I replaced the headpipe on this car, I used the aftermarket, copper-coated nuts sold by a vendor. I guess, at the time, I reasoned how much different can the aftermarket stuff be especially when the OE Volvo nuts cost fifteen times as much. I reasoned wrong.

So, my advice to anyone replacing those headpipe flange nuts: do yourself a favor and spring for the real deal, they are costly for a good reason.

Rich (near Pittsburgh)