I only looked at the years in question on the rack specs and they are the same by FSM year.  But, maybe, as you found, you have a 15:1 (actually 15.8) instead of 18.

Here's 1976, and 1977.  Maybe you have a 76 rack.  I don't feel so wimpy anymore.  I assume the higher number is higher mechanical advantage?  Not sure. 

Edited December 1, 20186 yr by Zed Head

1975 specs are the same as for 1976.

Are the steering knuckles the same length between these models. I wonder if they made the 280 cars have lower ratios to make the high speed steering less twitchy?

That's a good one.  Looks like the last change was 7/73 though.

http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Axle/Front-Axle

17 hours ago, rturbo 930 said:

Yes, the steering racks are different, someone on hybrdZ measured the travel per revolution on both racks, and the 240 rack was a little faster. However, to me, that would mean that the 240 would have heavier steering, but the opposite is true.

Can you point me to that thread? Would be an interesting read. And I agree... Seems counterintuitive, and would like to read that.

 

15 hours ago, Zed Head said:

Here's 1976, and 1977.  Maybe you have a 76 rack.

Zed Head, My 77 manual says 18.0 ratio. Both .pdf and hard copy. Are you sure you were looking at the 77 manual?

17 hours ago, wheee! said:

All good information and reasons I am using the AZC Shortened steering knuckles along with the Silvermine Power Steering kit on my rebuilt 76 280Z rack.

Exactly.

I was like all like T-Rex arms after driving Wayne's car at Zcon. Couldn't lift my elbows off my waist.  Thankfully there's still enough range of motion at the elbow to get the drink high enough to sip.

These work good for drinking and driving non power steering manual transmission cars.  Also pocket pool. 

1 hour ago, Captain Obvious said:

Zed Head, My 77 manual says 18.0 ratio. Both .pdf and hard copy. Are you sure you were looking at the 77 manual?

I posted a picture of the 77 18:1 below the 76 15.8:1, in my post #13.   By "as you found", I meant what you found in the early FSM.  I was trying to say that maybe you have an earlier rack, 1976, with the 15.8:1 ratio.  1977 was a change year.

I wonder if the gear changes might show up on somebody's parts CD?  It's not shown in carpartsmanual.com.

Is that hat available in period-correct colors?

19 hours ago, rturbo 930 said:

Yes, the steering racks are different...

Different between contemporary-build market/models too.

EG 1970 FSM for north American market HLS30U models gives rack ratio as 17.8:1 whilst 'rest of the world' got 15.8:1 and the 432-R model got the 'quick' knuckles as stock equipment.

4 hours ago, Captain Obvious said:

Can you point me to that thread? Would be an interesting read. And I agree... Seems counterintuitive, and would like to read that.

Here: http://forums.hybridz.org/topic/99017-240z-rack-into-280z/

240Z (1972) - 1.81" of travel per 360 deg of steering.

280Z (1976) - 1.5" of travel per 360 deg of steering

13 minutes ago, rturbo 930 said:

Here: http://forums.hybridz.org/topic/99017-240z-rack-into-280z/

240Z (1972) - 1.81" of travel per 360 deg of steering.

280Z (1976) - 1.5" of travel per 360 deg of steering

Sorry but, with respect (you are usually a saint in this respect, rturbo 930), "240Z (1972)" is not refined enough for this discussion. As I've pointed out, North American market got a 'slow' steering rack ratio from the get-go, whilst other markets got a relatively 'quick' ratio during the same period.

Market and/or variant needs to be specified if any of this is to be accurate.