67 Lifter problem

[Phillyfanfrombirth]

Yes.

Because your lifters are being pressured by hydraulics.

When you tighten them up, you press against the hydraulics of the lifter... the hydraulics will give way and yield to the pressure of the valve spring over minutes or hours.

Then, when you start your vehicle, your hydraulics lifters will "reinflate"... if you have your lifters too tight, it will keep a valve open for too long (causing backfires, poor vacuum, and possibly a bent valve, or a dislodged stud).

Do NOT tighten them again. Start the engine, and recheck the valves after letting it run for a minute or so. If the valves seem to be too tight, back off the pressure until you can once again spin the pushrod. I'd rather have it a little loose (spin freely), than too tight.