I just got my '68 327 2bbl on the road. Everytime it gets above about 3000 RPM (don't know for sure - no tach)I hear a hard rapping noise that seems to come from inside the engine. I adjusted the rocker arm nuts as per the Chevy manual for fear of loose rocker arm, but no dice. When I installed the oil pump I didn't attach the nylon ring to connect the pump drive shaft. That wouldn't cause that sound would it? The engine is really brand new with only about 90 miles on it. Do I need to bust off the pan and install that nylon ring, or could it just be a dirty lifter? Wouldn't a lifter make noise all the time if dirty? Thanks in advance.

Mabey piston slap. Has the block been bored? Does it happen when the motor is cold/hot or anytime?

If you don't get that nylon sleeve on (or, better yet, a Moroso or Milodon shaft with a steel sleeve), the shafts will separate at that joint, and you'll have no oil pump at all. Hope you're not hearing a rod knock.

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JohnZ
'69 Z28 Fathom Green