Split in Manifold Pressure.....Need Help

[billsheila]

I just had this same problem. It was a bear to get to the bottom of. Easy way to test the gauge is to swap the lines at the gauge, see if the problem follows the swap in which case the gauge is probably OK.

Remember that a leak in manifold is a higher reading since the gauge works on vacuum.

I ended up tracking mine to a small leak in one of the copper lines (there are like three sections front and rear). The leak was really hard to find because it was under a fitting. Sure didn't take much of a leak to create the MP split.

I agree with you it is worth getting to the bottom of. In my case the MP was off by about 3 inches at anything under about 20" (above that it didn't seem to make much difference). I found it very distracting.