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Front Engine P337H has low MP after start
I have 1979 P337H with american aviation intercoolers. Suddenly out of nowhere when I started it the other day the front engine manifold pressure was reading down at 15 inches rather than 30 or so I usually see. After starting the rear the front stayed at 15 while the rear held 30 as expected. As I advance power on the front engine the MP decreases an inch or two. When I feather the prop or bring the engine near cut off the MP increases a bit. The turbo is working fine and I don't believe it should be a factor while on the ground anyhow. I swapped the inputs to the MP gauge and the problem was the same on the (now) rear reading as well. Therefore I think the gauge has nothing to do with this. What could cause a vacuum to be created on the intake manifold of my front engine. I assume some sort of restriction is happening somewhere.
Any help would be greatly appreciated.
Brad
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