Rod Knock.... or No Rod Knock, That is the question! Options

[LvSteveH]

I recently picked up a very nice 912E with a 2.0L type 4 running stock L-jet injection. Didn't run well at all, I didn't really care at the price I paid. Upon doing the initial survey, I found about 10 quarts in the crankcase. The owners manual for the 912E is a dual 911/912E version, so I thought someone did the unthinkable and filled the old girl up to the brim. When I drained the oil, it was obvious that the excess was in fact fuel.

The compression check revealed a suspect cylinder, and sure enough, when I popped the valve cover, there was the rocker assembly laying there for the world to see. A rocker shaft nut backed off, then the stress caused the other one to snap the stud. Thanks to some very careful welding, I extracted and replaced the stud and got it all back together. On a curious note, when the engine was rebuilt in 1999, they "upgraded" to hydraulic lifters. I have no experience with hydro. lifters in a type 4. As good practice I went ahead and adjusted the valves (warm engine up, and before the lifters leak down, adjust to 1/2 turn past 0 lash).

Engine runs great, and after a little clean up and a clutch adjustment, it drives very very well. The problem I'm having, and the point of this post, is that I can hear a faint knock. So faint that most people couldn't pick it out, you really have to isolate the sound in your mind, but it's there. It's a bit deeper than a lifter tick, which it shouldn't have with hydros anyway. But the sound is fairly faint. I tried pulling plug wires one at a time, but the sound is quiet enough to be masked by the dropping of a cylinder.

It does not get any louder at higher RPM's, if anything, it blends in as the engine is sped up. Obviously I can just throw caution to the wind and drive it, or I could go ahead and pull it for a reseal and inspection. I just hate not being able to know one way or another. Everyone I know is just an occasional builder, more or less like I am, so I probably need someone who lives and breathes them to hear it. The main problem I'm having is that I never heard the car run any other way, so I don't know if it's just part of the engines awkward symphony, or if there an actual issue. I tried to compare the sounds with the 1.8L in the Dijon bomb before Ferg picked it up, and as near as I can tell, the sound I'm hearing is unique to the new car. Thanks!