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Thread: bought a 71 datsun 240z and i dont know anything about carbs

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    Default bought a 71 datsun 240z and i dont know anything about carbs

    Hello, i bought a 71 datsun 240z that has a l26 with i believe su carbs on it, and a 5 speed in it. I noticed today that there seem to be a couple of vacuum hoses that are either just open or plugged, i took some pictures to see if it helps someone figure this out. I hooked up the vacuum control on the distributor but really didn't notice any difference in the change of idle. The car is idling between 1000-1200rpm's after warm up, im not sure if thats normal or not. Also the car seems to be running really rich. also, is there a good manual that i can buy for this car that someone can recommend. Thanks for the help in advance.

    Thanks,
    Albert







    Last edited by 03redzo6; 10-09-2012 at 11:12 PM.

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    Formerly known as Koalia Reverend's Avatar
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    First of all, welcome to the club! Secondly, check out the SU-carbs section in this forum and use the search function, there is tons of info here for you to find. It seems you are missing the tube from front carb to distributor, it suppose to be attached on the manifold side of the carb. Other 2 tubes from the carbs supposed to be attached to original style airbox.

    Btw. you have exactly the same coil as i do
    -72 240Z "Goldie"

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    Hi Albert.
    Koalia is correct. There should be a vacuum hose from the inlet manifold to the distributor.
    Where does the hose in the last picture come from? If it comes from the inlet manifold, then remove the bolt, and determine if there is suction there with the engine running.
    If it doesn't, then attach a hose from the unused fitting near the centre of the manifold to the dizzy.
    Idle should be 7-800 RPM or thereabouts.
    Haynes put out a good book---DATSUN 240z & 260Z OWNERS WORKSHOP MANUAL. Lots of good reading there.
    Your engine has carbs from a 240Z, which will run well. Someone has swapped in a 260 and put 240 carbs on there. Originally 260 was fuel injected.
    Hoses from the carbs are merely breathing tubes, and as Koalia said were plumbed into the air cleaner box.
    Tie them away from the exhaust, and shorten them a bit if you want.

    Brian.
    Last edited by olzed; 10-10-2012 at 01:34 AM.

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    The 260 was fuel injected? I thought it had flattops?
    1971 240Z HLS30-38691
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    Now with 100% more DATSUN SPIRIT L28 Power
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    Quote Originally Posted by Zedyone_kenobi View Post
    The 260 was fuel injected? I thought it had flattops?
    The US 260Z used flattops. It was not fuel injected from the factory.
    73 240Z
    74 260Z

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    There were two different 260's in North Am. Early one with flat top carbs like 73 240 (though not identical), skinny bumpers with hydraulic shocks, and then a later one with FI like 280 and bumpers like the 75 280. The interiors for both were the new 280 style dash and console. Real Heinz 57.... No wonder folks restoring 260's have a devil of time finding parts for them!

    Nice Z BTW. I like the red wire that comes through the firewall at the choke cable grommet and goes to the coil best. I'm pretty that's not stock... and worth understanding what it bypasses (like the ignition switch....).
    Last edited by zKars; 10-10-2012 at 07:51 AM.
    -----------------------------------------
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    We sell a dvd that will help shorten your learning curve on the Hitachis (SUs made under license for the Japanese makes). You could for very little money go through them, clean 'em up and get them running in some known state to see what you really have.
    JUST SUs ZTV09 for twenty five of your hard earned dollars.

    Whatever you do don't plug the hoses that come off the top of the float bowl lid. Those need to be open to the atmosphere. Is there anything hooked to the vacuum advance canister on the distributor? Are you running a points distributor of and electronic distributor. If you are running an electronic distributor and there is no vacuum advance hooked up at the canister it may be because the EI Dist was over advancing with vacuum hooked up..
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    Quote Originally Posted by zKars View Post
    There were two different 260's in North Am. Early one with flat top carbs like 73 240 (though not identical), skinny bumpers with hydraulic shocks, and then a later one with FI like 280 and bumpers like the 75 280. The interiors for both were the new 280 style dash and console. Real Heinz 57.... No wonder folks restoring 260's have a devil of time finding parts for them!
    Late 260Z in the US still had flat tops. Not FI. That was actually the probable reason for the late 260Z - the fuel injected L28 wasn't ready yet, so the late 260Z was the rest of the 280Z package but still using the carbed L26.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
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    Download the FSM from the "Reference" section of xenons30.com, everything you need is in there. The Haynes book is woefully underwhelming.
    2/74 260Z

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    I prefer the FSM over the Haynes manual.
    Europe, Aus, NZ and South Africa never saw the 280Z. They just went further with the 260z and FI until the 280ZX. The 280z came out to try to combat the extra weight due to the heavy bumpers and the tougher emision regulations in CA.

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    Quote Originally Posted by Zedyone_kenobi View Post
    The 260 was fuel injected? I thought it had flattops?
    Oops, late night brain fade. I was thinking of the Fairlady 2000 JDM private imports we got down here. I have seen flat top carbs and fuel injection on them.
    Depending on the year I suppose.

    I actually got up at 1am to try to edit that, but was unable to connect. More brain fade perhaps.
    Last edited by olzed; 10-10-2012 at 11:54 AM.

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    Arne, thanks for the clarification. All 260's were flat top carbed. No FI. thanks!
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

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    Hi Albert:
    First - as others have mentioned - a 240Z Factory Service Manual is the best thing to have.

    Second.
    See this picture - you can see where the vacuum hose hooks up for the distributor vacuum advance.
    http://becksystems.com/KellyW/162KellyW.jpg The vacuum advance on the distributor uses Ported Vacuum just behind the Carb - ahead of the intake manifold.

    Third - the hose off the top of the Carb Float Bowls is a vent - it would normally hook to the stock Air Cleaner - but as I recall the aftermarket round cleaners have a hole in the back of them for a connector. I wouldn't suggest venting the float bowls toward the exhaust manifold.

    Fourth - the last picture shows a line from the Gasoline Vapor Emission Flow Control Guide Valve - that used to run to the Stock Air Cleaner - that line lets fresh air into the system, to allow heavy gasloine vapors to get out of the cannister in the rear of the car - - - Unplug that and leave it open. No need for the hose if it isn't connected to an air cleaner

    Fifth - the vacuum ports on the Balance Tube - between the Carb's - should be properly sealed off if not used.

    Post some pictures of the rest of the Z - and tell us why you bought it to begin with.

    FWIW,
    Carl B.
    Last edited by Carl Beck; 10-10-2012 at 12:58 PM.

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    Quote Originally Posted by Koalia View Post
    First of all, welcome to the club! Secondly, check out the SU-carbs section in this forum and use the search function, there is tons of info here for you to find. It seems you are missing the tube from front carb to distributor, it suppose to be attached on the manifold side of the carb. Other 2 tubes from the carbs supposed to be attached to original style airbox.

    Btw. you have exactly the same coil as i do
    Thank you, and will do. I hooked up the distributor vacuum to the carb manifold but I didn’t notice any change in anything.

    Quote Originally Posted by olzed View Post
    Hi Albert.
    Koalia is correct. There should be a vacuum hose from the inlet manifold to the distributor.
    Where does the hose in the last picture come from? If it comes from the inlet manifold, then remove the bolt, and determine if there is suction there with the engine running.
    If it doesn't, then attach a hose from the unused fitting near the centre of the manifold to the dizzy.
    Idle should be 7-800 RPM or thereabouts.
    Haynes put out a good book---DATSUN 240z & 260Z OWNERS WORKSHOP MANUAL. Lots of good reading there.
    Your engine has carbs from a 240Z, which will run well. Someone has swapped in a 260 and put 240 carbs on there. Originally 260 was fuel injected.
    Hoses from the carbs are merely breathing tubes, and as Koalia said were plumbed into the air cleaner box.
    Tie them away from the exhaust, and shorten them a bit if you want.

    Brian.
    Hello, I unplugged it but there is no vacuum or air coming out. It seems to be coming from this blue tube that’s connected to the block. I’ll be getting a haynes book then, thanks. I got the idle down to 950rpm but any lower and the car shuts off.




    Quote Originally Posted by zKars View Post
    There were two different 260's in North Am. Early one with flat top carbs like 73 240 (though not identical), skinny bumpers with hydraulic shocks, and then a later one with FI like 280 and bumpers like the 75 280. The interiors for both were the new 280 style dash and console. Real Heinz 57.... No wonder folks restoring 260's have a devil of time finding parts for them!

    Nice Z BTW. I like the red wire that comes through the firewall at the choke cable grommet and goes to the coil best. I'm pretty that's not stock... and worth understanding what it bypasses (like the ignition switch....).
    Thanks for the heads up, I’ll look into it. This car came with a push start button, but I want to uninstall that.
    Quote Originally Posted by LeonV View Post
    Download the FSM from the "Reference" section of xenons30.com, everything you need is in there. The Haynes book is woefully underwhelming.
    I’ll go ahead and do that, thanks.

    Quote Originally Posted by Bruce Palmer View Post
    We sell a dvd that will help shorten your learning curve on the Hitachis (SUs made under license for the Japanese makes). You could for very little money go through them, clean 'em up and get them running in some known state to see what you really have.
    JUST SUs ZTV09 for twenty five of your hard earned dollars.

    Whatever you do don't plug the hoses that come off the top of the float bowl lid. Those need to be open to the atmosphere. Is there anything hooked to the vacuum advance canister on the distributor? Are you running a points distributor of and electronic distributor. If you are running an electronic distributor and there is no vacuum advance hooked up at the canister it may be because the EI Dist was over advancing with vacuum hooked up..
    I’ll go ahead and order one today, thanks. There wasn’t anything hooked up to the vacuum advance canister but I hooked it up to the carb manifold but didn’t notice any change. I’m not sure if this picture will help with your question but here it is.

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    Second Picture from the last at Post #15 - the Top hose on that Flow Control Valve should go to the Air Cleaner or be left open - it draws in fresh air. The Bottom hose goes to the Crankcase Vent... the flow control valve directs gasoline vapors to the crank case - where they are sucked back into the intake manifold by the PCV valve.

    FWIW,
    Carl B.

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    Quote Originally Posted by Carl Beck View Post
    Hi Albert:
    First - as others have mentioned - a 240Z Factory Service Manual is the best thing to have.

    Second.
    See this picture - you can see where the vacuum hose hooks up for the distributor vacuum advance.
    http://becksystems.com/KellyW/162KellyW.jpg The vacuum advance on the distributor uses Ported Vacuum just behind the Carb - ahead of the intake manifold.

    Third - the hose off the top of the Carb Float Bowls is a vent - it would normally hook to the stock Air Cleaner - but as I recall the aftermarket round cleaners have a hole in the back of them for a connector. I wouldn't suggest venting the float bowls toward the exhaust manifold.

    Fourth - the last picture shows a line from the Gasoline Vapor Emission Flow Control Guide Valve - that used to run to the Stock Air Cleaner - that line lets fresh air into the system, to allow heavy gasloine vapors to get out of the cannister in the rear of the car - - - Unplug that and leave it open. No need for the hose if it isn't connected to an air cleaner

    Fifth - the vacuum ports on the Balance Tube - between the Carb's - should be properly sealed off if not used.

    Post some pictures of the rest of the Z - and tell us why you bought it to begin with.

    FWIW,
    Carl B.
    Thank you, that picture was very helpful. ill check later for the hole in the carb filters. As far as the line from the Gasoline Vapor Emission Flow Control Guide Valve, would it be ok if i found a way to hook that up to the carb filter, or should i just leave it alone and unplug it.

    Ill take a picture of it later and post it but i have to warn you, it needs a lot of work, but at least it runs. Im 26yrs old now and i first saw one of these cars when i was about 8yrs old, i remember it looked so cool, after that i never saw another one again. I sold my 03 Z06 a couple of days ago so i can use that money for a down payment on a C6 Z06 but i couldnt resist, so i picked up this little thing as a project so i can restore it to its former glory.

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    Quote Originally Posted by 03redzo6 View Post
    Thank you, and will do. I hooked up the distributor vacuum to the carb manifold but I didnít notice any change in anything.
    You shouldn't. At idle there is no need for vacuum advance in the distributor. You should feel vacuum on that line if you open the throttle and run the engine at higher RPM's. Vacuum Advance should advance the timing under load and back off at cruise or steady RPM's.

    [QUOTE=03redzo6;412327]Hello, I unplugged it but there is no vacuum or air coming out. It seems to be coming from this blue tube thatís connected to the block. [QUOTE=03redzo6;412327]

    That Blue Tube is the Crankcase Vent - the small tube on it - should be hooked to the bottom line on the Flow Control Valve. It is there to suck gasloine vapors into the crankcase.

    FWIW,
    Carl B.

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    Quote Originally Posted by Bruce Palmer View Post
    We sell a dvd that will help shorten your learning curve on the Hitachis (SUs made under license for the Japanese makes). You could for very little money go through them, clean 'em up and get them running in some known state to see what you really have.
    JUST SUs ZTV09 for twenty five of your hard earned dollars.

    Whatever you do don't plug the hoses that come off the top of the float bowl lid. Those need to be open to the atmosphere. Is there anything hooked to the vacuum advance canister on the distributor? Are you running a points distributor of and electronic distributor. If you are running an electronic distributor and there is no vacuum advance hooked up at the canister it may be because the EI Dist was over advancing with vacuum hooked up..
    I second everything that Bruce said. Maybe I am dense, but I couldn't get my head around the SU until I saw the video.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Quote Originally Posted by 03redzo6 View Post
    Thank you, that picture was very helpful. ill check later for the hole in the carb filters. As far as the line from the Gasoline Vapor Emission Flow Control Guide Valve, would it be ok if i found a way to hook that up to the carb filter, or should i just leave it alone and unplug it.
    Yes - it would actually be best if hooked to the carb air cleaner. If not - it at least has to be open to draw in fresh air.

    I'm sure that you will enjoy the Z - they are fun to drive and very easy to work on. Once they are in proper condition - they are very reliable as well. Not to mention that they are always beautiful to look at.

    FWIW,
    Carl B.

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    [QUOTE=Carl Beck;412338]You shouldn't. At idle there is no need for vacuum advance in the distributor. You should feel vacuum on that line if you open the throttle and run the engine at higher RPM's. Vacuum Advance should advance the timing under load and back off at cruise or steady RPM's.

    [QUOTE=03redzo6;412327]Hello, I unplugged it but there is no vacuum or air coming out. It seems to be coming from this blue tube that’s connected to the block.
    Quote Originally Posted by 03redzo6 View Post

    That Blue Tube is the Crankcase Vent - the small tube on it - should be hooked to the bottom line on the Flow Control Valve. It is there to suck gasloine vapors into the crankcase.

    FWIW,
    Carl B.
    Carl, why would you want to suck gasoline vapors INTO the crankcase?
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    Personally I wouldn't want to. However as part of the Gasoline Vapor Emission Control System - gas vapors from the tank are collected in that cannister behind the Right Rear Quarter. That cannister is there to allow the vapors to condense back into liquid form when they get dense enough. The vapors that remain are sent up to the engine compartment - to that Flow Control Valve. They are sucked into the crank case when there is a negative pressure there - then redirected to the intake via the PCV system - to be sucked into the combustion chamber. So the crank case is just a place to suspend them until they can be put back into the combustion process.

    This was all originally part of the California emissions control regulations - but soon became part of the Federal Standards.

    Give a bureaucrat an inch and they will always take a mile and demand more. They can not ever let their job be DONE.

    FWIW,
    Carl B.
    Last edited by Carl Beck; 10-11-2012 at 03:04 PM.

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    Quote Originally Posted by Carl Beck View Post
    Personally I wouldn't want to. However as part of the Gasoline Vapor Emission Control System - gas vapors from the tank are collected in that cannister behind the Right Rear Quarter. That cannister is there to allow the vapors to condense back into liquid form when they get dense enough. The vapors that remain are sent up to the engine compartment - to that Flow Control Valve. They are sucked into the crank case when there is a negative pressure there - then redirected to the intake via the PCV system - to be sucked into the combustion chamber. So the crank case is just a place to suspend them until they can be put back into the combustion process.

    This was all originally part of the California emissions control regulations - but soon became part of the Federal Standards.

    Give a bureaucrat an inch and they will always take a mile and demand more. They can not ever let their job be DONE.

    FWIW,
    Carl B.
    So if you aren't worried about emissions, you could rip all that stuff out and just plug the vent tube @ the tank?
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