Waking the sleeping beast?

[mikemeade]

Allright, so back to the matter at hand... Does anyone know the sizes of the fuel hoses in the engine compartment? I would like to replace them before I go about turning this engine over this weekend. The hoses I have seem to be two different sizes. They are pretty old and cracked though, so I would be nervous about finding an exact match.

Also, do all the fuel lines need to have the insulation all over them like mine seem to have?

[nealkeith]

Mike, with the special hood vents, and all that insulation on the fuel lines. I would venture to say that your car experienced some severe vaporlock problems at some point in time.

[Carl Beck]

Hi Mike:

Get on the phone and call some local Auto Parts Stores.. and ask them if they carry metric fuel line sizes. When you find one that does - simply cut a 6 inch piece off the different size hoses that are on the car and take them to the store with you.

As the car seems to have the earlier SU's now - no you shouldn't need to retain the fuel line insulation.

FWIW,

Carl B.

[mikemeade]

I searched around last night on this board and others and settled for 1/4" and 5/16" lines. The 5/16 is also labeled as 8mm. The 1/4" is 6.35 mm. I figure that the 6.35 mm lines are return lines, so it shouldn't matter if they are oversized right?

Also, the first picture above shows an orange line leading from both of the float bowls, crossing the engine, and then terminating at the bottom of the engine compartment. As far as I can tell, this is the overflow for the float bowl. (that is how it works on the British SUs anyways). So my question is, is this where the return line to the tank is supposed to fit in? Is there a return line somewhere in the fuel rail that is covered by insulation? I replaced all the lines I could see last night, and everything seems to fit properly.

[=Enigma=]

The orange lines are definitely connected to the float bowl overflows, however these normally terminate at nipples on the rear of the stock air cleaner housing. Since this car no longer has the stock air cleaner, the PO extended them and ran them out the bottom of the engine compartment. If I were you, I would figure out a way to do this with your existing air cleaners, find a stock housing, or at least put a filter if some sort on the end and make sure it's not routed to close to the exhaust. Someone who has had to deal with this might have some other ideas.

[Carl Beck]

I searched around last night on this board and others and settled for 1/4" and 5/16" lines. The 5/16 is also labeled as 8mm. The 1/4" is 6.35 mm. I figure that the 6.35 mm lines are return lines, so it shouldn't matter if they are oversized right?

Hi Mike:

The US sizes will work - the only problem is that they are in fact slightly larger or smaller and thus you have to either tighten to hose clamps down more than you would have with the proper metric sizes, or streeetch them more than you should have... that in turn cuts into the exterior rubber on the larger hose and weakens them right from the beginning.. in the long run they will crack/leak at the clamps sooner, than if the clamps didn't have to be tightened so tightly to begin with, or the opening stretched so much on the smaller hose. It's no biggie... but I just happen to have kept my Z for a very long time... long enough to see what the difference is between using US and metric sizes, after replacing them several times.

Also, the first picture above shows an orange line leading from both of the float bowls, crossing the engine, and then terminating at the bottom of the engine compartment. As far as I can tell, this is the overflow for the float bowl. (that is how it works on the British SUs anyways). So my question is, is this where the return line to the tank is supposed to fit in? Is there a return line somewhere in the fuel rail that is covered by insulation? I replaced all the lines I could see last night, and everything seems to fit properly.

The fuel return runs though the metal fuel rail... On the engine you will see that the Fuel Rail has two lines at the front - one connects to the fuel pump and the other connects to the metal return line on the front frame rail.

As mentioned - yes -the orange lines are breathers for the float bowl. If you look closely at the air cleaner bases you have - you might see that they have a die-cut stamped in them - where you can punch them out and put a fitting in to connect the breather lines. (depend on what Brand Name they actually are). If you don't see a die-cut stamped in them, you can just drill a hole and put a fitting in them...

Good luck,

Carl B.

[mikemeade]

It sounds like what the previous owner did is fairly appropriate then. The overflow line ends at the fram rail underneath the battery and is nicely tied back to the car. I may eventually plumb this a little better, but I don't see a problem with the general idea. Why would I need a filter at the end of the hose? I can't imagine any significant dirt making it's way through the six feet of hose uphill and into the float bowls.... Or is there some other reason?

[mikemeade]

Hi Mike:

As mentioned - yes -the orange lines are breathers for the float bowl. If you look closely at the air cleaner bases you have - you might see that they have a die-cut stamped in them - where you can punch them out and put a fitting in to connect the breather lines. (depend on what Brand Name they actually are). If you don't see a die-cut stamped in them, you can just drill a hole and put a fitting in them...

Good luck,

Carl B.

Thanks for the help. Why would the overflow hose go to the air cleaner? If the carb overflows, the filter would get soaked with fuel, and probably draw less air, providing a very rich running situation... Wouldn't it just be better to get rid of the fuel like the previous owner did?

[Carl Beck]

It sounds like what the previous owner did is fairly appropriate then. The overflow line ends at the fram rail underneath the battery and is nicely tied back to the car. I may eventually plumb this a little better, but I don't see a problem with the general idea. Why would I need a filter at the end of the hose? I can't imagine any significant dirt making it's way through the six feet of hose uphill and into the float bowls.... Or is there some other reason?

Routing the breather to air cleaner - allow the gas vapors to be sucked into the intake - rather than released into the air. The 240-Z's were originally equipped with a Gasoline Vapor Recovery System... to meet EPA requirements.

Carl B.

[Carl Beck]

Thanks for the help. Why would the overflow hose go to the air cleaner? If the carb overflows, the filter would get soaked with fuel, and probably draw less air, providing a very rich running situation... Wouldn't it just be better to get rid of the fuel like the previous owner did?

I don't believe it is actually an "overflow"... it's a vent or breather.. to prevent gas vapor from building up in the float bowls and effecting the float level.

If the float sticks open for some reason, the fuel level in the bowl will raise above it's prescribed level... and it will run into the carb flooding the engine first... The level of fuel in the float bowl is set to hold the fuel level at the top of the nozzle in the carb... that's why float level is so important to tuning the SU's.

Liquid reaches it's own level - and that small formed vinyl hose that connects the float bowl to the bottom of the carb is very specifically designed to allow the fuel level in the float bowls to maintain an equal level of fuel at the carb nozzle. That is why it is not recommended to replace that formed vinyl line with a piece of rubber fuel line.

FWIW

Carl B.

[mikemeade]

Thanks Carl,

That makes a lot of sense. I suppose it would clean up the engine bay a bit if I rerouted those vents to the air cleaner. Once I get the car running, I will have to add that to my to do list.

Mike

[ChrisA]

Hi Mike,

Some of the guru's here can tune their carbs with only the service manual for help. They are far better than I. I got the tune up video from www.ztherapy.com to help me and watched 10 times!

ztherapy can help you a ton if you need them. They can rebuild your carbs or swap yours for a rebuilt set they have on hand.

I believe they might be able to get you a factory air cleaner assembly also.

FWIW,

Chris A.