Hello, all.

About a month ago, my 2003 Dakota with the 4.7L, ejected a rocker on the #5 cylinder. Happened when I finished work and started it up... immediately ran rough and gave misfire codes. I pulled the valve cover and found the rocker sitting unscathed and luckily, no damage anywhere else. I found that the cause was a seized hydraulic lifter (lash adjuster), so I went about the task of replacing all the lifters. Along with those, I'm replacing all the valve springs and stem seals. The thing has about 314K mi on it, so way overdue for these things.

So, I got the passenger side bank done using one of those Miller tools to compress the valve spring. I used one of those valve holders that you thread into the spark plug hole and hook up an air compressor to keep the valves from falling.

I'm now on the driver's side bank, which is cylinders 1,3, 5 and 7. When I air up each cylinder on this bank, I'm losing loads of air coming out the throttle body. It's flowing out so fast that I have to hurry and get the spring compressed and the keepers back on before the valves fall. The compressor will drop to zero while running eventually. So far 3, 5 and 7 have exhibited it, so I'm sure 1 will do it too. This was not the case with the other bank, as they held the pressure. The fuel rail and injectors are removed, if it matters. Also, all the rockers are removed, so the valves are all closed. Any idea why I'm losing all this air? The truck drove fine, with what felt like loads of compression, prior to all this.

What am I missing here?

Thanks in advance