Fisch's '71 510 LZ22 - "Chapman" Fogs and Bre Spook+art

[MicroMachinery]

When it happened to me, my float had sunk. Each carb has one; mine sunk because the linkage/hinge inside the float bowl was bound.

[fisch]

When it happened to me, my float had sunk. Each carb has one; mine sunk because the linkage/hinge inside the float bowl was bound.

That makes sense. I was thinking since the 240 carbs have solid rubber floats it wouldn't fill and sink, but I wasn't thinking about the hinge! I will cross my fingers it is that easy a fix.

[MicroMachinery]

I hope so, too. Good luck!

[fisch]

Cracked open the overflowing fuel bowl on my front SU carb.

 

Interesting... My understanding is that this float should not rest all the way down on the lid when the lid is upside down. I am suppose to bend a tab on the float hinge that will engage the needle valve long before it gets this high. Plus if it travels this high, the float is probably getting caught on the side of the bowl. Possibly sticking, or at the very least, stopping before it can fully close the valve.

 

I am a little confused about what level it should be at. Watching the 'Just SU' video says to set it to level that will engage a Grose jet, but this doesn't have the Grose Jet. I understand Z-Therapy doesn't use them any more, so we are back to the old fashion needle jet that came with the carbs. But I read on a site the needle jet needs a different height than the Grose Jet. I am trying to figure it out.

 

But it would seem this float level was never set? Which is kinda surprising with all the work the PO did on this car, even replacing all the screws will allen heads. The other thing that has me worried is that the two carbs need to have the same float setting to really run best. SO now I am wondering about the other carb, even though it seems to be working fine.

 

Any thoughts are appreciated. i will try to set it as is, but I've read that putting a plastic tube on the drain hole as a gas sight might help dial the level in. I am finding this site very useful and hopefully it will get me there. http://www.zcarz.us/TechnicalInformationPageCarburation.htm

 

[fisch]

OK so from what I am reading the way to set the float level with a needle valve is to make the gap between the float and the bottom of lid 14-15mm when it shuts off the valve. You check this by holding the lid, float down and blowing through the gas inlet and raising the float till is shuts off your airflow. That should be 14-15mm and you bend then tab accordingly.

 

So I guess that is next.

[MicroMachinery]

Yeah.. that pic of the float bowl cover upside down looks like it would easily lead to a flooding situation. Looks like you're on the right track.

[mklotz70]

You might want to pull the needle out of there and look at it.  There's typically a rubber cone....or at least a cone on the brass piece.  If the rubber is deteriorated, that's how it was set correctly by the PO, but is no longer correct.  The float should not be hitting the top like that.....the needle has to seat and seal before it gets to the top or it will never shut off the fuel.

 

From what I understand on the SU's, float level is important, so you will definitely want to do the other carb too!!  Even if you fix this one and think it runs good, you'll always wonder if it could be better by doing the other carb.....just just do it now while you have the tools out and it's fresh in your mind. :)

 

If you think it runs strong now....wait 'til the carbs are dialed in.....you might pee yourself :)

[fisch]

You might want to pull the needle out of there and look at it.  There's typically a rubber cone....or at least a cone on the brass piece.  If the rubber is deteriorated, that's how it was set correctly by the PO, but is no longer correct.  The float should not be hitting the top like that.....the needle has to seat and seal before it gets to the top or it will never shut off the fuel.

 

From what I understand on the SU's, float level is important, so you will definitely want to do the other carb too!!  Even if you fix this one and think it runs good, you'll always wonder if it could be better by doing the other carb.....just just do it now while you have the tools out and it's fresh in your mind. :)

 

If you think it runs strong now....wait 'til the carbs are dialed in.....you might pee yourself :)

Interesting theory about the rubber bit missing, so now it is a different height Mike. So where was this rubber? Inside the valve? I did do the test where I blew into the gas inlet and raised the valve with my finger till it shut off the air. It worked in that test. But that doesn't mean it wouldn't engage sooner if there were a missing bit of rubber in there.

[Jester]

This is what a fuel needle valve (left) and seat (right) are suppose to look like. Keep in mind this is just a random image off google. Your SU needle may vary slightly. 

 

 

The needle valve sits in the seat. (the part that screws into the carb between the float pin towers) There is a tab on the back of the float that is attached to the needle. As the float is raised because of incoming fuel, it shuts the fuel off by raising the needle into the seat.

After you are finished blowing everything out really good, pull the needle assembly out of the carb and inspect the end of the needle. The black portion should be nice and flat along the run of the tip. Make sure when you re assemble it, that the needle is able to make a nice seal. If you simply hold the carb body just as you did in the picture, and set your float level LEVEL with the mounting surface of the float bowl, you my find yourself pretty close to where you need to be. 

[fisch]

Thank you Jes! So here is what we got. That is a bit of a ridge along the bottom of the cone. I got it to seal when I blew into it, but if there was rubber, it is long gone. Anyone ever have one of these open to compare? I am thinking it should be replaced.

 

[mklotz70]

The polished tip should seal okay......so it just looks like it's not adjusted correctly.  I agree with Jester about the adjustment unless there's better info in the SU video.  Check the same stuff on the other carb and if that float is not touching when held upside down, adjust this one to match it.

 

The rubber piece is more or less the 'new' type.  Many years ago, it was just the brass point.

[dgi]

Todays ethanol blended gas tends to create problems with the rubber tips on float valves.

 

Yours is the original brass type and much preferred then and now.   If it seals it is OK.  Just adjust the float properly and continue.

[fisch]

Awesome, because I was having trouble finding a source for just the needle/seat.

 

Also I've noticed the rebuild kits out there don't have a gasket for the float bowl? I see ZTherapy lists them. And they are cheap, but I am impatient, lol. I have gasketmaterial so I may just cut one. But the chamber is pretty thin lipped. I remember hearing folks cut gaskets out of brown paper bags too. Anyone else familiar with that? Would be easier to cut!

[MicroMachinery]

I've never heard of that, but it may just be crazy enough to work!

[fisch]

So this was unexpected. THis is the rear float. The front was overflowing. This one was not. I measured the gap when right side up by blowing through inlet and raising the float till it sealed and taking the measurement. Not really scientific, but the results were interesting.

 

It appears the rear float shuts off the gas when it is 5mm from touching the lid. The front was even lower at like 2mm before it would shut off. My understanding is that they should shut off the gas at 14-15mm from the lid when held right side up. (If I have this wrong please correct me!) Remember 240Z carbs, not 510.

 

So if the minimum this is off is 10MM from stock. Would that not mean the gas is 10mm higher in the float bowl than it should be. Therefore inside the carb body, the gas is 10MM higher than it should be? Which would naturally make things rich. And in the case of the front, where I don't think it would ever seal because the float would hit the inside of the bowl before it could reach 2mm from the lid, we'd have overflow?

 

Wondering if there is a reason to set the floats this high? Or if the pressure inside the fuel bowl, with gas sitting for a year or more, could bend the float tab this much?

 

Rear Float

[dgi]

I have gasketmaterial so I may just cut one. But the chamber is pretty thin lipped. I remember hearing folks cut gaskets out of brown paper bags too. Anyone else familiar with that? Would be easier to cut!

  You are an artist!  You can probably do this perfectly.

 

If I did that the results would look like my stick figures, not very realistic.   :rofl:

[goes2fast]

Awesome, because I was having trouble finding a source for just the needle/seat.

 

Also I've noticed the rebuild kits out there don't have a gasket for the float bowl? I see ZTherapy lists them. And they are cheap, but I am impatient, lol. I have gasketmaterial so I may just cut one. But the chamber is pretty thin lipped. I remember hearing folks cut gaskets out of brown paper bags too. Anyone else familiar with that? Would be easier to cut!

I don't think that is a good idea for a carb, would absorb too much gas, and leak. Stick with gasket paper.

[Jester]

I used an old Pepsi case for transmission gaskets when I pulled my old 5 speed apart. Never did leak. 

 

Seriously, call Steve at Z Therapy. He is usually at the shop around noon, our time. He loves to help people. Especially those that have his carbs and video. His shop is about 10 minutes from my house. 

 

Z Therapy

503-365-8583

[goes2fast]

I used an old Pepsi case for transmission gaskets when I pulled my old 5 speed apart. Never did leak. 

 

Seriously, call Steve at Z Therapy. He is usually at the shop around noon, our time. He loves to help people. Especially those that have his carbs and video. His shop is about 10 minutes from my house. 

 

Z Therapy

503-365-8583

Gear lube is a lot thicker than gas.

[fisch]

Gear lube is a lot thicker than gas.

Yes infact I looked up where I heard that and it was the well respected MG guru from Uniersity Motors who did the paper bag gasket, BUT, as y'all have suspected, it wasn't for the carbs, it was specifically for the gearbox.

[mklotz70]

You can get thin gasket material at the local parts store.

[qwik510]

Have you tried to get in touch with Chris, the PO and ask him? He knew those carbs pretty well. He might have some insight.

[fisch]

Have you tried to get in touch with Chris, the PO and ask him? He knew those carbs pretty well. He might have some insight.

Actually, yes, I wrote Chris out of the blue this week to get some insight, and as you'd expect, he has been awesome! He really helped me understand the SU system, and confirmed that indeed, Chapman's raked stance actually does cause a syphoning effect when you change the fuel filter cause the gas tank is higher. Maybe all 510s are this way? He also mentioned that he tried the ball valves/Grous jets the use to come with the z therapy carbs but could never get them to seal. And after talking with ZT they thought maybe the vibrations, which are a lot in Chapman's case, simply kept opening it. So the needle valves solved it.

 

About the carb floats, he is pretty sure he set them, but can't remember how or what he did. The only way he says we will know for sure if their height was on purpose, is to check the gas level with a site. But the more I think about it the more odd it seems to set the one so high it won't seal. All I can imagine is that in the sitting and shaking this car does, I mean that cam really rattles the whole car, Something changed.

 

As you know he is out of Datsuns, but is living the dream being a part of a drag race crew!

[fisch]

The latest discovery. I don't think I have a fast idle screw. It appears my intake does not use the stock K14 linkage at all! Just a cable stop attached to it. So it must be using a modified 240Z shaft linkage, and nothing else.

 

Watching the 'Just SU' video, I believe he mentioned the only time he really uses the fast idle is to tune the carbs at hi rpm, then he backs it off. But I guess if I had it is is an easy way to bump the idle up.

 

Another interesting thing I am seeing is that there is no PVC hooked up at all and I don't see how the crank case is breathing. THe hole for the breather tube is plugged with a bolt. What issues might this be causing?

 

I actually see exhaust coming out of the rear carb upon shutdown. Is this normal?

 

 

In this shot if you look under the cable pulley you can see the manifold cross tube, and the spot for what I think should be the PVC valve is just blocked off. There is another bolt in the block where I think the breather tube might go. The thing is, with these headers on the z22 block It barely looks like there is room to get a breather tube on there. My oil pressure gauge seems to be operating in an acceptable range. But there is oil seeping from the valve cover. I'd assumed it was from an old gasket.

[goes2fast]

Crank case definitely needs to be vented, filter on the valve cover, and PVC hooked to intake manifold. Good air in, bad out! :thumbup: