Question about the Z's engine installation: What is the cant angle?

[Namerow]

We all know that the Z's engine is canted off vertical.  However, I've been unable to find any diagrams or tech info that indicates, definitively, what the cant angle is.

Does anyone know the engine's cant angle?  An, if so, what's your source?

[HS30-H]

Cant angle is 12 degrees, as stated in various Nissan technical publications (none of which I seem to have to hand at this moment...).

 

[Namerow]

Thanks.  In the absence of any other information, I had taken some measurements from a drawing that appears in the 1970 FSM (see below) and came up with 11.9 degrees... so I was close.  Good to have this confirmation.

[siteunseen]

Does this affect valve adjustment in anyone elses opinion? Seems like the base of a lobe would hit full on the valve stem later with the tilt of the motor?

I put center lines on top of the cam towers to use as my "straight up" reference point when pointing the lobes up for adjustment.

I'm trying to make sense of this so any and all of your opinions would be very much appreciated. 

 

 

[Namerow]

14 hours ago, siteunseen said:

I put center lines on top of the cam towers

How did you determine 'top'... Was it the inertial* top?  Or was it the geometric** top?

* 'Inertial top' = the point where a carpenter's level would rest if levelled and placed on top of the tower circle. 'Inertial' is the same as 'plumb'.

** 'Geometric top' = the point where, when viewed from the front of the engine, a line drawn perpendicular to the top face of the engine block (head gasket surface) and going through the camshaft centre intersects the top of the tower circle.

If you use the inertial top to gauge TDC with the cam lobes, you'll be off by 12 degrees.  If you use the geometric top, you'll be ok.

For an inline engine with normal architecture, all of the relationships between moving parts are based on an X-Y axis going through the centre of the crankshaft, where the Y axis drawn along the centreline of the cylinder bores (plumb 'vertical') and the X axis is perpendicular to the Y-axis (plumb 'horizontal'). 

When an inline engine is mounted in the vehicle with no cant angle, the X axis runs parallel to inertial/plumb horizontal and the Y axis runs parallel to inertial/plumb vertical.  Picturing or calculating where all the parts sit when Cyl. 1 is at TDC is easy.

When the engine is canted to one side, picturing or calculating where all the parts sit remains easy if you also cant the X-Y axis by a matching number of degrees.  Having done so, the X-Y axis becomes an X'-Y' axis, and is 'relative' rather than 'inertial'. 

In other words, you have to adjust your frame of reference so that it's canted, or rotated, by the same amount as the engine block.  If, on the other hand, you try keep your frame of reference aligned with 'plumb', things get messy.

EZ-to-understand example of how this plays out:  You're reassembling your L24 engine on an engine stand and have the engine rotated on the stand so that the cylinder bores are plumb vertical.  You find TDC for Cyl 1 by rotating the crankshaft until the piston is at the top of its travel and the two cam lobes are pointed up.

Edited May 17 by Namerow

[siteunseen]

I used a straight edge from the end closest to the firewall to the front to make my marks.  So I know I'm over thinking this but it makes sense to have the lobes pointing up and even with the center of the cam towers to set my valve clearance. I realize the whole motor tilts so if it is installed upside down the lobes should still be in line with the center of the towers, right?

Thanks for your reply