The FSManual has the diagram that shows all the frame dimensions on it. It is all in metric and at the bottom there is a baseline near the rocker panel that everything is measured from. The question is where is the line on the car at the bottom of the rocker or at the bottom of the body flange below the rocker? I am going to the frame shop in the morning and need to check all the frame dimensions.

Thanks, Charles

The attachment may help. It seems the author had the same difficulty as you and assumed the bottom of the floor was the reference. I looked at '72 to '78 FSM's and could not find the reference stated. Datsun only shows drawings and it looks higher than the frame rails for certain however I would have assumed it to be the bottom of the rocker pinch-weld. If the rocker pinch-weld is lower than the frame rails then it can not be the reference.

I hope this helps.

240Z-chassis-jig.pdf

Edited September 6, 201311 yr by Blue

Hmmmm

I looked closer and it seems the reference datum line (red) is below the floor (blue) so maybe I was correct and the bottom of the rocker pinch-weld is the vertical reference?

Have a look:

Edited September 6, 201311 yr by Blue

That was great Blue. thanks for that. That makes perfect sense about the pinch welds. I assume that document is now part of the database now, so I can always find it since I'm in it . I love the burn marks from splatter on his notes.

Charles

PS The car went to our frame man today and he said it was an 1" out so I was glad I took it...

How do you know which line is the floor line? I guess I can measure from the tranny support and compare that to the 86 mm to determine what the reference is...?

C

The floor line has the frame rail (floor support) welded to it. This is clear to see in the drawing at least!

Here is another that uses the floor: 240Z frame drawing sketchup - Blogs - Classic Zcar Club

I am now leaning to the datum line being the floor because the frame rail rises above the floor in the large groove behind the rear seat mount and because the seat mounts rest on the red line.

Edited September 6, 201311 yr by Blue

So the line you high lighted in blue must be the hump in the floor board which comes back near the rear seat supports. That would also explain the little angle at the rear of the frame rail coming up to the dashed line you high lighted because it comes up into the hump at the rear. Agree?

C

Yes, after a lot of review I agree

Thanks for the help last night Blue. I picked the car up today. He had it all squared up and level. The bolts for the front bumper are not exactly right but if he pulled that section it would throw off the fender. I'll make the bumper work. He said the car had been pulled before and that it had been hit in the front from the drivers side. The dimensions of the factory diagram are "more like guidelines anyway..." the tension rod sockets were different from the diagram by 10mm but both were even and he said they hadn't moved. Also the shock towers were 10mm higher than the diagram. There evidently were some fairly large tolerances on frame assembly as long at it was all even.

Charles

In one of the other threads Blue posted one of the guys found a similar discrepancy in the rear frame rails...

C

Glad to help!