Hey All,

I hope someone can help me out, this is a rehash from another Z forum, but I'm spreading it in the hope of finding a solution.

I'm in the early stages of restoring a 71 240z and thought a chassis jog would make life easier. As of now, step one is creating headaches, as described below.

As of now i have built a chassis jig/frame and am in the process of bolting up my bent 240z to it. And here is the rub.

I spent countless hours pouring over the only chassis dimensions document out there. That being the BF-3 204z dimensions PDF.

As described previously I was thinking that the dimensions are wrong, or my car is very, very bent. With what I describe below, I don't think the car can possibly be 'that' bent.

Some framing of the problem, with a crap pun:

I have used four mounting points (described from rear to front):

(1) Rear diff mount (not mustachio bar), (4 lateral bolts)

(2) Front mount to the rear lower control arm, (4 lateral bolts)

(3) Transmission mount, and then (two lateral bolts)

(4) Front Strut Tower Top ("A" point).

The dimensions (that don't work):

(1) Reference point.

(2) 465mm from ref. (1). this one is 15mm to short. (closer to 480mm)

(3) 1427.5mm from ref. (1). This one lines up.

(4) 2381.3mm from ref. (1). This one is 20mm to short. (closer to 2401.3mm)

To my point......what the heck is going on here??!!

Between point ref 1 and 2 my car is 480mm. In the BF-3 document, there is no reference to a 480mm dimension.... The car cannot be warped by 15mm, it's all structural mounting points. So, what am I missing?

Moving on to the dimension between 1 and 4. Again, too short by 15 to 20mm... So, what is the actual dimension?

All of the lateral dimensions are correct.

I scratch my head. It's great though as it gives me something to talk with my wife about over dinner.

Thank you in advance!

Ok. Replying to myself in order to hopefully help someone else out in the future.

This was SUPER painful to work out but the correct measurements were.

From back to front:

Rear of rear lower control arm mount to front of rear lower control arm mount: 456.5mm. This is 465-15+6.5mm.

Next is rear of rear lower control arm mount to gearbox mount:

1434mm. This is 456.5+15+962.5mm

The last one is from the rear of rear lower control arm to the strut towers. Mathematically its 2387.8mm.....

This is the number that doesn't work. It comes from 456.5+15+1585+331.3.

With my car however this number is closer to 2401mm.

For the above 4 points the vertical reference is from rear to front.

285mm,

69mm

86mm, and

130mm. (To underside of front frame rails).

I've mounted the car, its very stiff and ready to be deconstructed ....

Edited 6 hours ago6 hr by Timwell

Is it possible that you've misinterpreted the reference point for the 465mm measurement that appears in FSM drawing? The way I read the drawing, that 465mm measurement defines the distance from the so-called 'C-point' to the centreline of the moustache bar's chassis mount bushings (if you look really closely, you'll see the moustache bar's circular end loops defined just to the rear and inboard of the rear shock tower chassis mounts). Let's call this location on the vehicle the 'E-point'.

The 'D-point' refers to the centreline of the top of the rear struts . But, according to the FSM drawing the centreline of the top of the struts lies directly above the centreline of the 'gearcase mounting rear crossmember' (which is a more useful reference point when taking measurements off the vehicle).

The D-point sits 450mm aft of the C-point

The E-point sits 15mm aft of the D-point (so 465mm aft of the C-point).

The photo below (source?) provides a good visual reference for what all this looks like on the underside of a bare Z structure.

As far as I can see (I could be wrong), the FSM drawing makes no attempt to provide dimensions for the location of the rear lower control arm and its mounting points. You'd need to construct your own layout drawing for the diff, moustache bar, and rear suspension in order to specify (in mm) the locations of the rear lower control arm and its mounting points relative to the C-point.

Edited 2 hours ago2 hr by Namerow