-TheBandit-

iTrader: (1)

If a VVT engine (LY6, L92, etc) has no significant oil pressure, i.e. cranking on a stand for a compression check, will the VVT cam default to full advance or retard and will it be stable enough for a starter-cranking compression check?

3pedals

iTrader: (3)

default is to full advance. there is a lock pin that holds it in that position if no oil pressure is inside the phazer, no matter what signals the ecu is sending to the phaser control solenoid.

-Joseph-

iTrader: (12)

The lock pin holds it within about +/- 1.5 degrees of full advance, it does have a bit of slop. It is not meant to actually run like that for any significant timeframe, long enough for oil pressure to build and then the lock pin moves away. As you can imagine, a phaser cannot hold the camshaft in a set position without oil volume.

I have not performed a compression test on a VVT engine, but I see no reason that you cannot get consistent results if the same cranking procedure is used from cylinder to cylinder. I may just give it a try myself to see if there is any difference.

SweetS10V8

iTrader: (4)

Ive done a compression test on and L92 and had no inconsistencies or issues. You just dont want to run the engine with the VVT unhooked.