Well I've confirmed the tank size in my roadster is not the standard 60 liter (15.9 gal.) unit. It's 13.2 gals.
In trying to get my fuel gauge to work, found the float stem was bent causing it to be stuck in the 3/4 to full position. Removed and manually moved up/down and gauge moved full E to F range. Bent stem back and reinstalled. Worked but then went only to 1/4 after filling tank. Think I'll order a new sender.
Anyway, it's in this exersize that I confirmed the tank size. Put 3 gals. in and then filled to top and total was 13.2+ gals.

Tank is in all appearances an oem tank. The only thing I can surmise is that because this was a Canadian new car delivery, it had a European thank which happens to be 13.2 gals.

Can anyone verify this as a possibility? Thought it to be an interesting tidbit to add to Z members drives data base.
Jack

_________________
John D .... original 240 past, 260v8Roadster current

Anyone have a sender for EARLY 260?
Jack

_________________
John D .... original 240 past, 260v8Roadster current

I could be wrong, but my understanding has always been that z-cars had the 13 gallon tank up until 1976, and then the tanks were enlarged by means of using a "space saver" spare tire. A 75 or 76 tank is a well sought-after part for 240 owners trying to convert to fuel-injected motors, as these tanks will fit the 240 but have the improved baffling needed for fuel injection. They do not have greater volume. In other words, I'm pretty sure your smaller 13 gallon tank is normal for your car.

_________________
71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

Nope. My original early 240 had a 15.9 gal. tank. This one caught me
by surprise. My belief is that North american tanks were 60 liter/15.85 gals but EU cars had 13.2 gal. tanks.

_________________
John D .... original 240 past, 260v8Roadster current

Jack, *how* did you confirm your tank was 13gal? The standard 260 was a 16gal (60L) tank:

["The Datsun 260Z was powered by a 162-bhp, 2.6-liter six-cylinder engine featuring a single overhead cam, two valves per cylinder and a four-speed manual gearbox or a three-speed auto. The engine generated 152 pound-foot of torque at 4,400 rpm and featured a bore and stroke of 3.2 inches and 3.1 inches, respectively. The 260Z could hit 60 miles per hour in eight seconds and go on to 127 mph. The fuel tank could hold 16 gallons and averaged 24 mpg; the car's range was estimated at 350 miles"].

But because of the unique shape of the tank, the little 3-gallon 'cupola' or 'turret' on top might not get filled if you have a clogged fuel vent, making it only possible for you to put 13gal [+/-] in an empty tank.

I'll try to find a diagram to show what I mean.

Frank

_________________
1970 240Z

Your correct. What I read was EU cars had 13.2 gal. tanks, but that was
UK gals. ..... same as 16.9 gals.
Your thought about a clogged vent is a good one. drained tank when removed sender, had 3 gals. exactly. Put the 3 gals. back in and filled the tank and can only get 13.2-13.4 gals. in.
How does one check or unclog the vent. But if the vent was clogged would the tank not make funny noised when being filled or would that just outgas thru the filler tube? This could be a really good thing if I can get the extra 3 gals. because of the V8 range can be an issue.
Jack

_________________
John D .... original 240 past, 260v8Roadster current

Well, not only will a clogged fuel vent prevent you from completely filling the tank, it will also prevent you from using what fuel you CAN put into it. As your V8 empties your "full" (13gal) tank, a clogged vent will prevent air from entering the tank to replace the exiting fuel, so eventually you will get a low air pressure cloud ('vacuum') above your fuel, which will fight against your fuel pump. Your engine will actually starve for fuel and sputter and even quit. When you open the filler cap, you'll get a WHOOOSH as air rushes in to refill the vacuum. Then it will run fine again for awhile, until you use enough fuel to create another vacuum above the fuel level. Then the struggle will resume again ~ fuel pump trying to pull fuel out of the tank, vacuum trying to keep it in.

Your fuel pump is maybe rated at what? 4lbs? It doesn't take much fuel drop for your tank to counteract that with 4lbs of vacuum on top of your fuel level working against the pump, and pretty soon you get fuel starvation problems. One of our members actually had his clogged tank collapse due to such vacuum!

No fair asking me anything about the 260 fuel system. Those tanks are such a mystery to me that I could get lost back there. There are so many fuel hoses and vent hoses and return hoses and overflow hoses and vapor hoses and every other kind of hose back there, I am only barely functional with them. Sorry.
There are real experts on here tho, and they can tell you which hose is the fuel vent line, and how to get the Mud Dauber nest out of it.

_________________
1970 240Z

Frank,
In thinking about your clogged vent line hypothesis, I do know that I've emptied this tank 2 ways. 1st was to run it out of gas, then was able to refill to 13.2 gals. 2nd was the drain it/fill it method, still only to 13.2 gals.

It would appear that there was not enough vacuum to overwhelm the fuel pump as same end point was reached. I suppose it's possible to have a partial clog whereby the tank won't fill completely as it fills quickly while allowing enough flow to allow tank to release fuel at the slower rate as in normal use consumption.

I have a new sender unit coming in, so when I'm able to draw fuel down to install this I'll take a look at the lines.

Jack

_________________
John D .... original 240 past, 260v8Roadster current

I'm sure by then you'll find someone in the Club who knows these tanks well, and who can tell you which line is the vent and where it is likely to be clogged. Sorry I can't.

_________________
1970 240Z

It's just hard to believe your knowledge base is limited in this area.
Oh well! Guess we all have our limitations.

_________________
John D .... original 240 past, 260v8Roadster current

Every Z fuel tank I've ever seen has been different than the others, and that includes that stupid kidney tank (vapor tank) behind the passenger seat, *IF* the car even has one. There seem to be so many combinations of hoses and kidney tanks that it leaves me baffled. Any time I think I learn something about one of these tanks (which line goes where), the next tank I see doesn't even have the same number of hoses or vent pipes in the tank. That includes tanks made in the same model year.

I simply accept the fact that there are more combinations involved in these tanks than my tiny Brain Housing Group can comprehend.
A man's got to know his limitations.

_________________
1970 240Z

What did you eventually find out about this, Jack?

Frank

_________________
1970 240Z

I haven't yet. I replaced the sending unit. When out of the tank moving the sending float un and down made the gauge move, however, when installed gauge only reads between 1/2 and 3/4. Last time I did this tank was drained and exactly 3 gals. was put in. I filled it and was only able to get 10.2 gals. in yielding 13.2 gals. I did some research and found the UK cars had 13.2 gal. tanks, however, further research found that was imperial gals. which equated to the std. 15.9 gals. So, I have not had the gumption to drop the tank in fear of breaking a hose or connection since I have no leaks and spring came. I do find credibility in your thought of a vent plug limiting imput. Engine is able to get enough fuel as the rate is relatively slow, but when filling fuel goes in quickly. I don't have the patience to try VERY slowly adding fuel to see if there is enough vent to allow air to escape and I doubt it would work anyway. I think the only answer is dropping the tank and checking all the hoses. Not something I want to invest time or $'s now.
I thought about possibly doing a gentle roater router down the vent at the fill neck but have not yet figured out what to use that would be flexible enough, stiff enough and gentle enough.
Jack

_________________
John D .... original 240 past, 260v8Roadster current