I've had this 77 280 Z floating around in my garage for years and years now. It's in boxes mostly and I have flirted with putting a variety of engines in it. I've even bought 3 engines and then changed my mind and sold them. (20B, 13B TT, & SR20DET).
I also have a spare, slightly wrecked 2001 S2000 that I've been reserving for another project. I think you can see where this is going.
I've played extensively with the S engine in an Ultralite (Lotus 7 type car) and know how it really wakes up when you remove a few pounds. It gets scary fast! So while the Z wouldn't be as light as my intended project dropping 500-600 lbs would make the Z really perform and be a nice little sleeper, right?
Having moved the Z around so many times I know it's pretty light so I decided to see just how much weight I'd be shedding to put the S engine in the Z. Imagine my shock when I discovered it's barely lighter than a 2002 S2000 and HEAVIER than a Miata! It seems there's not a lot to be gained by S-ing the Z.
77 280 Z weight 2630 lbs.
2002 S2000 weight 2864 lbs.
1999 Miata weight - 1999 Miata weight 2299 lbs.
Back to the drawing board, so tell me again how bloated new cars are.
how much of the Z's weight is in the engine? that long 2.8 I6 cannot be light.
I looked into putting my Fiat on a diet.. when I discovered that most of it's weight is in things that would require fabrication to lose weight.. like sheet steel headlight buckets, brass radiator, and a lot of metal where a modern car would use plastics
My MG didn't gain any weight when I installed the LS1 engine and T56 transmission along with widening the track and reinforcing the chassis out the wazoo. I guess horsepower is weightless 
Turns out the stock engine was massively heavy and the front subframe and suspension shared more with bridge engineering than car engineering. Unsprung weight and semi-sprung weight was not a concern in Jolly Old England.
Shaun
HalfDork
9/18/12 9:04 p.m.
According to the same site linked the 240Z comes in at 2301. I remember at the time thinking that the 280 z was bloated. I drove one once and was very disappointed-
The engine is an absolute boat anchor. I haven't put it on a scale, but when I moved the rotaries, SR20 & the S engines around they move easily but the Z engine is ponderous.
I'd always had this bright idea of removing the strut suspension (never mind that I have completely new struts, springs, poly bushings) and replacing it with a modern IRS subframe. But I'm thinking the subframes would be heavy enough to offset any weight loss by an engine swap. Of course the engine would be set back quite a bit further than the stock so weight distribution would be great.
With the 20B sitting in the engine bay both my son & I could stand in the engine compartment in front of the engine at the same time.
I thought the 280Z was more or less the same body as a 240Z and the real changes came with the redesign for the 280ZX, no?
As I remember it the weight increases in the -74-78 came from 2 things.
1) the early bodies were flexible and they kept strengthening it up until the ultimate one which was the 1978.
2) adding the crash resistant bumpers.
I almost pulled the suspension out of the 93 RX7 I had and chickened out at the last minute thinking that I must be stupid since no one had ever done something like that. Turns out I was ahead of my time.
Now that I have this spare S2000 it seemed like a no brainer till I found out about the weights. I think I'd rather have an S that looked like an S (or a Locost) rather than an S that looks like a 280Z. I am just really amazed at how heavy the Z is or maybe it's how light the Miata & S2000 are.
All day long I've been cooped up in the cab of a truck with nothing to do but think. I had it all mapped out down to learning to do a little body work to flair the rear fenders to clear the Kinesis rims I've got. BUMMER!
So if the answer isn't Miata on this list there's only one other thing to do LSX!
Unfortunately that means it won't happen this year. What's one more year when you've waited 10 already, I guess. This was going to make my wife VERY happy.
Look at most of america and you will have your answer.
I'd imagine you will drop several hundred pounds from the engine alone. A 2400lb Z car with 240hp would be fun in my book.
Add another 50lbs of turbocharger and a 350hp 2450lb Z car would be really fun.
You could get a base model EVOX that weighed... wait for it... wait for it...
3050lb curb weight. 
Now, I dunno about you, but a 1995-ish STi bone stock is pretty fast, and they make WAY less torque than a EvoX and usually don't run very "crisp". An EvoX that weighs 3050 must be a rocket!
carguy123 wrote:
The engine is an absolute boat anchor. I haven't put it on a scale, but when I moved the rotaries, SR20 & the S engines around they move easily but the Z engine is ponderous.
Well, it is a former Mercedes design (taken from Mercedes and given to Japan after the war). So yeah, heavy, old school design, built by the Japanese.
Beautiful sounding motor though.
If you design the subframe support structure well, you can lose some of the weight in the towers and fender wells. I wonder if a newer Nissan might be a good donor? Or would you go with a Miata/RX-7 solution?
This is what I get for reading the Godzilla SR article in the magazine during lunch. Wicked Evil thoughts.
There's not a lot of weight in the towers and fender wells. The strut itself is heavy, but the control arms are very light duty.
ProDarwin wrote:
I'd imagine you will drop several hundred pounds from the engine alone. A 2400lb Z car with 240hp would be fun in my book.
But it wouldn't be more fun than an S. There are lots of improvements that have come down the pike since the 70's. Unless there's a big increase in performance (as opposed to an S) then it's not worth the work. Weight had everything to do with making this attractive.
The other project I had in mind for the S drivetrain and suspension should drop 800-1,000 lbs. because all I was going to do was Locost like and connect the subframes by a tube frame and go play. Nothing fancy, just a toy.
I think an S2000 engine in a Miata would be pretty fun. The biggest problem would be the height of the engine. It's been done once or twice.
carguy123 wrote:
This is what I get for reading the Godzilla SR article in the magazine during lunch. Wicked Evil thoughts.
No joke. 
Personally, I wouldn't go after a 240 with the thought of using it in the same sentence with an S2000 or Miata. Tech has come too far to compare modern mid-range sports cars to 40-year-old mid-range sports cars. Instead, I'd build a 240 simply for the sexy lines and exhaust note, and the shortcomings in handling and nimble-ness are part of the romance of owning a classic sports car (IMO).
carguy123 wrote: Back to the drawing board, so tell me again how bloated new cars are.
The 280Z is bloated compared to the 240Z. Significant weight difference.
Plus, I would not be surprised if literally a quarter of the weight is engine.
turboswede wrote:
Well, it is a former Mercedes design (taken from Mercedes and given to Japan after the war). So yeah, heavy, old school design, built by the Japanese.
No, it isn't. That's an often repeated myth. But the cast iron block is incredibly heavy. I cannot lift a bare one by myself. Even the crank is amazingly heavy. A modern aluminum engine would drop a ton of weight from the front of the car.
Wiki info on the engine
Overall, the weight of a 280Z is not that much of a difference over the 240Z. It got rolling upgrades that some guys eventually do to their 240Zs like the R200 rear end and bigger/stronger frame rails. The crash bumpers weigh about 80lbs more than the early 240z bumpers. I know, I've weighed all the parts when swapping them onto my '75 280Z. The EFI stuff added some significant weight, as did the door crash bars and some the heavier substructure of the unibody. The suspension has bigger struts to handle all this extra weight and that added some weight by themselves. If you backdate a 280Z by removing the big bumpers, the EFI system and doing some simple lightning work I figure that you can drop a few hundred pounds which makes a big difference.
Looking at an early S30 Z car (70-78) and the new Scion/Subaru twins makes you appreciate how much work it was to get all the new safety gear and modern conveniences into such a light chassis.
