I too would be suspicious of the exhaust repair.
On the other hand, I have a B20 that was a "rapper" when I purchased it.

I knew nothing of the history of the car, but under the valve cover was evidence that the previous owner (I bought it from an auction) neglected many oil changes. Quite a bit of hardened crud on top of the head.

I was willing to rebuild from the start but figured on trying to see if I could narrow down the noise before opening up the engine. Threw a pint of automatic trans. fluid in with the regular crankcase oil and ran it around for about 500 miles. Then changed the oil and refilled with another pint of ATF and the remaining 10W-30. Ran that around for about 1000 miles. Amazing that the loud rapping noise disappeared and the top of the head and valve train cleaned up nicely as well. I definately believe it loosened up or cleaned up something internal also.


Don't get me wrong, this engine is still tired, but that was also about 25,000 miles ago. I would never do this unless I was resigned to a complete rebuild anyway.

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'60 544, '68 220S, '70 145S, '72 144E, '86 745T