| Dollar-bill Test [message #352485] |
Fri, 28 February 2020 13:02  |
uprooted
Messages: 72
Registered: December 2019
Location: Hilliard, OH
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I was excited to find that the "official" engine health checks on our 455 seem to be great... good oil pressure, compression @150 each cylinder, 40+ cm Hg, and hand holds perfectly steady on vacuum gauge. However I've discovered that it fails the "dollar bill test". When you hold a piece of paper very close to the exhaust pipe, the paper will slap against the pipe. It is erratic in how often it happens. Ranges from once every 2 or 3 seconds to several times per second. The implication here is that one or more exhaust valves are not seating fully and the intake stroke sucks in some exhaust. How is this possible if the compression test checked out? The 455 has headers and what appears to be factory type exhaust, 2 muffler, y pipe, 2.5" pipe to rear. Exhaust crossover is blocked according to my inspection with a borescope with carb off.
I want to tell myself that the numbers dont lie, but I cant ignore the fact that exhaust gas is moving in the wrong direction momentarily!
Corey P /
Hilliard, OH /
1974 Glacier 26' /
3.70 FD /
ION Wheels
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