HELP su conversion

[justin260z]

I converted my 260z to a 4 barrel, and now I want to convert it to the older round tops. The problem is I dont have the linkage connecting them together, AND I dont know what all the stuff on the carbs go to IE vacuum lines. Please help I dont even know where the fuel lines go.... Im in over my head with this one.

[e_racer1999]

the fuel lines go to the nipples on the banjo fittings.

the only vacuum lines that i have hooked up are the ones to the float bowls, the one to the brakes, the vacuum advance line, and the block vent hose thing (not the PCV, although it will be hooked up soon)

as for the linkage you can get them from Ztherapy.

[MikeW]

The lines to the float bowls are not vacuum lines but rather fuel overflow lines in case a needle gets stuck open on the inlet side. While they dump the overflow into the air cleaner they really serve no real purpose.

[justin260z]

The lines to the float bowls are not vacuum lines but rather fuel overflow lines in case a needle gets stuck open on the inlet side. While they dump the overflow into the air cleaner they really serve no real purpose.

So should I just plug those off?

[MikeW]

So should I just plug those off?

I think it would be better to run them to the air cleaner as was originally intended. If the needle valve gets stuck open the float bowls will start overflowing and can start spilling fuel directly onto the exhaust manifold. Routing it to the air cleaner will hopefully cause some of it to be sucked into the engine although some might also drip from the air cleaner onto the manifold.

[justin260z]

This is my current setup. Can I tun the su carbs with my egr blocked off?
Basically I want to bolt them onto the car & run fuel lines and be done with it, Is that possible with what I have, or do I need to go shopping?

http://i85.photobucket.com/albums/k63/justin260z/S5030702.jpg
http://i85.photobucket.com/albums/k63/justin260z/S5030701.jpg
http://i85.photobucket.com/albums/k63/justin260z/DSC_0398.jpg
http://i85.photobucket.com/albums/k63/justin260z/DSC_0397.jpg

[Bruce Palmer]

... plug those overflow nipples. Bad things will befall you...... they must vent to the atmosphere. I hink w have some photos on the ZTherapy.com website that showswhat your final lashup should look like.

What are you doing for an aircleaner??

[justin260z]

I'll probably get either those spring loaded foam thingys, or a pair of K&N's. That would be awesome if you could get those pictures, Bruce.

[=Enigma=]

Looks to me like you're gonna need some linkage depending on what's on the SUs now, as well as a fuel rail which is missing. See pics for some clues.

[justin260z]

Well Enigma, I already have the linkage that is attached to the firewall.... I just modified that to work in the 2 barrel. And I plan on making my own custom fuel lines. Thanks for the picture, it helped me out a lot.

Will the su carbs work poorly if they have no fuel return line?

[DaveN]

Re float bowl vent lines --

Their main purpose is to keep the pressure over the gas in the float bowl exactly equal to the pressure around the carburetor inlet. Any mismatch changes fuel flow, so those tubes have to be vented to the inside of the air filter.

[=Enigma=]

Well Enigma, I already have the linkage that is attached to the firewall.... I just modified that to work in the 2 barrel. And I plan on making my own custom fuel lines. Thanks for the picture, it helped me out a lot.

I was referring to the linkage that connects the linkage you have(firewall to manifold), to the linkage between the carbs.

[beandip]

What Palmer said is true about plugging the vents to the float bowls. Clean air is important , this is another reason to vent them into the air cleaner. Now to your question of vacuum lines . The front carb. has a port that is for the vacuum advance on the Dist. , one line must go to the vacuum booster on the master cylinder. The vent line with the PVC valve comes from the block and is attached to the intake balance tube. The vent from the valve cover is supposed to also connect to the air cleaner. If you add one of the little cute filters to this vent it is likely you will have fumes in the cabin. When run into the air cleaner the engine will burn these fumes. The stock air box has tuned velocity stacks installed for performance also , another reason to use it. One more thing , there is a fresh air return line that runs form the gas tank to the front of the car. It runs to the driver side up to where the ignition coil area is. On a 240 it connects to a divert valve . One small 1/4'' hose connects to the air cleaner and supplies fresh clean air to the main fuel tank as needed , one connects to the crankcase vent . This little valve is a one way valve that allows air to the tank and will restrict flow from the tank. If this is blocked the fuel tank will starve for air as the gas is drawn to the engine. Unless the seal is bad on the gas cap. If you don't use this valve or do not run the supply line to a clean air source dirt will be drawn into the tank. Be SURE to use gas rated fuel line , not vacuum line for all gasoline use. Injection rated gas line is not necessary because you are only dealing with at most 5 psi. Gary The OEM fuel rail has a function as a metering of the return line to the tank. The return line is important so that cool gas keeps running through the supply to prevent ''vapor lock'' .

[Bruce Palmer]

Across the board, front to back, top to bottom, good information all on this topic. A lot of internet info is worth exactly what is charged, but this time y'all nailed it!!

[justin260z]

My dist. has no vacuum advance. jeez... Im going to end up spending another $300 just on crap I need to make these carbs work. Oh, and I make my custom fuel lines from bulk brake lines, will that work?

[MikeW]

My dist. has no vacuum advance. jeez... Im going to end up spending another $300 just on crap I need to make these carbs work. Oh, and I make my custom fuel lines from bulk brake lines, will that work? The vacuum advance has nothing to do with making the carbs work. It has to do with making the distributor work. The front carb is just the source of the vacuum. If your distributor does not have a vacuum advance then just plug the small hole in the carb.

[justin260z]

Well, I finally got around to putting the carbs on. All I did was bolt 'em on, and start it and it runs fine. It idles rough, but maybe thats because it has no air filter and the carbs need a good tune.
http://i85.photobucket.com/albums/k63/justin260z/DSC_0422.jpg
http://i85.photobucket.com/albums/k63/justin260z/DSC_0423.jpg
http://i85.photobucket.com/albums/k63/justin260z/DSC_0424.jpg

And I put on my other hood (it has no hole)
http://i85.photobucket.com/albums/k63/justin260z/DSC_0425.jpg

[Fuzz260z]

hey just read this thread, im doing the same kind of thing to my car. Enigma i noticed in the pic u posted, the fuel rail had no heat protection, is this a problem?cheers
Fuzz

[e_racer1999]

justin - you might want to put thicker carb spacers on...also, get the ZTherapy carb video. worth every penny.. and then some! i also noticed the lack of a fuel return line. i woule address that

fuzz - the early 240zs didn't have heat protection on the fuel rai from the factory. they seem to be ok with little to no vapour lock