cracked exhaust
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,195
Likes: 3,085
From: NW AR
I noticed no change in sound or performance at all. The mufflers I had on were OEM with the centers punched clean through, which gave a nice note, but not too loud. In other words, I could still hear the radio. I've had a history of some backfiring on deceleration for a very long time. I thought the joint at the muffler/pipe was causing it. I now suspect it was sucking air at the crossover. The thing to do is to visually inspect it every so often. Loosen the cover if you have to and look under there.
What I think happened to me is that when I stopped for gas, some water, rest up a bit near Mitchel S.D., on a hot day (of course) after a long run on 90, the motor must have stopped "just right" with the exhaust valve open a little, and it cooled "just right" the valve guide and not the head yet, and I hit the start button at just the right (or wrong) time and the valve guide pushed out of the head with the valve. There's nothing holding that valve guide in the head but good intentions and a few thousand's interference fit, BTW. So the moral of the story is: Visually inspect that crossover pipe.
What I think happened to me is that when I stopped for gas, some water, rest up a bit near Mitchel S.D., on a hot day (of course) after a long run on 90, the motor must have stopped "just right" with the exhaust valve open a little, and it cooled "just right" the valve guide and not the head yet, and I hit the start button at just the right (or wrong) time and the valve guide pushed out of the head with the valve. There's nothing holding that valve guide in the head but good intentions and a few thousand's interference fit, BTW. So the moral of the story is: Visually inspect that crossover pipe.
Road Warrior
Joined: May 2009
Posts: 1,945
Likes: 3
From: Victoria, Australia
In my case (and as Dr. Hess mentioned) it was decel pop that gave it away. I did put up with it for a while thinking the head flanges were a little loose-- which they were but only a little).
Also there was a sooty looking discoloration along the crack lines where the leaking exhaust was coming from so it was very easy to see as well.
Road Master
Joined: Aug 2010
Posts: 1,205
Likes: 18
From: SE Michigan
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