240ZMan

If you mean the one between the manifolds and the carbs, then yes. Of course, it's for a 73 and I have 72 carbs, but I didn't think that would matter.

Frank13, thanks for the suggestions. You made an interesting point regarding the cause and effect of the rich mixture at idle vs. engine speed. Not sure if this matters, but when the engine compartment doesn't have the extra heat in it, the idle speed is rock solid at around 700 rpm and very smooth. As the heat builds up it starts to stumble intermittently, and gradually slows to 500 rpm or less. FWIW, before I put the rebuilt carb bodies on, my throttle shafts were leaking and under these conditions the idle would slow so much that it would eventually stall. I have confirmed that the pvc valve is loose and appears to flow well. I have a new hose on it as well. The spark plugs look just fine. They have that nice tan color and are even across all 6. Like I said, it's only at idle, and only when the heat builds up in the engine compartment. I have a feeling I've overlooked something, or made a bad assumption somewhere, but as I've been chasing this since last summer, I'm having a hard time bringing a fresh perspective to it. Any other thoughts? Thanks in advance!

I've tried running both the mechanical and electric together, separately, and even bypassed the mechanical just to run the electric alone. There was no difference I could notice. I did mount a fuel pressure gauge in the engine compartment for a week or so and found that fuel pressure wasn't any differenct when the stumbling occured. I also tried running the engine with the return fuel line into a cup and the flow seemed reasonable. Also, when the tank is full, at idle I can hear the fuel returning into the tank. At this point I've concluded that my fuel delivery system is ok, given I'm out of ideas of what to check next. You mentioned a "blower" from a 280zx. I'm not familiar with that. Can you describe it? Not sure from the sound of it that it would solve the underlying issue, but it might give me another clue.

I have an ongoing issue that I have run out of ideas trying to fix. I have a 73 240 with 72 carbs. The symptom is the following: when the engine compartment heats up enough, the engine begins to stumble at idle and sometimes eventually stalls. The rest of the time all is fine. For example, if I drive around the block a few times and then park in the garage and let it idle, and the air temp is above 60 degrees or so, after several minutes the idle will begin to slow down below 500 rpm and inconsistently change speed up and down. The exhaust will begin to smoke a bit as well. If I open the hood and let it idle within a few minutes all is well as things cool. Today I tried an experiment when it began to stumble. I gradually turned the mixture screws in until they were all the way closed. Most (not all) of the stumble went away and the smoking was reduced. My conclusion is that something is causing my idle mixture to go too rich when the heat under the hood rises. Of course, with the mixture screws all the way in it didn't want to drive worth a darn. Here are some of the things I've tried with no change: - new ZTherapy carb bodies, nozzles, hoses, float chamber needle and seats. - rebuilt the rest of the carbs per their tape. - bought another set of used carbs, rebuilt them, same issue. - checked fuel pressure when problem occurs. With mechanical only, pressure is 3-4 psi. With the electric only (I bypassed the mechanical), pressure is ~2.5 psi. - replaced fuel filter. - electronic iginition timing is solid at 12 btdc at idle. - bypassed hot water to intake manifold. - I can blow back through the fuel line from the gas tank without too much effort. - I removed the return fuel line and ran into a cup to make sure there was good flow and the fuel in the rail wasn't getting too hot. - The PO looks to have had all the fuel lines around the gas tank replaced as the cloth around them looks brand new and they are supple. - checked to make sure the nozzles are all the way up when the choke is off. What really confuses me is that both sets of carbs exhibit the problem. The only common element is that the 2nd set of carbs didn't have floats so I swapped them over. Today I tried raising and then lowering the levels almost 1/4" but it made no difference. Given that it's winter and we don't have too many warm days this is more of an iconvenience (and annoying!). But when the spring comes I know this is going to become a major issue when driving in stop and start traffic. Any suggestions?

Actually, it was MSA's catalog I was ordering from. I was looking for 16-8015 as I have a 73. The part number you mentioned says it's for a 74 in the catalog I have so I didn't ask about that part. I have some 5/16" fuel line and the bend doesn't look too bad, so I'm not going to look further. After all, that portion of the coolant circuit is only for the intake manifold.

I know it's a bda idea to use coolant/windshield washer hose for fuel, but what about the reverse? I am replacing the hoses on my 73 and the hose between the thermostat housing and the balance tube of the intake manifold is no longer available. It looks like I should be able to just use some 5/16" fuel line for the short distance.

Sahunt66, What oil to use in the carb dampers seems to get the widest range of answers possible. I'd suggest you experiment. I found this summer (when I picked up my 73 with 72 carbs) that 20W was the best. But when it got cold (below 30) that I did better with Marvel. The main thing I noticed was how smoothly the engine responded to the throttle starting up from a stop sign. A thinner oil seemed to give a quicker response, but if the carbs weren't rich enough, there was a little stumble as it temporarily leaned out too much. Using a thicker oil in the summer compensated without having to run too rich. Like I said, I'd experiment. It's no big deal to pop the domes off and pour out the old oil. Try one oil for a week and see what you learn. After all, that's supposed to be part of the fun of owning a 30 year old car:classic:

I put a new one in tonight and the needle is steady now. Definitely one of the easier (and cheaper) fixes so far... :classic:

On my 73 I've noticed that recently the ammeter bounces around a lot. Usually happens when I have the lights and/or fan running (ie. more load), but there are also times when the needle is rock solid in the center with them on, and then when I turn them off it starts bouncing. I cannot find a consistent cause and effect for this. I saw this thread: http://www.classiczcars.com/forums/showthread.php?s=&threadid=1868&highlight=ammeter and last weekend thought I would open up the voltage regulator and clean the contacts. But the PO had swapped it for a solid state unit. I opened it up and all looks well, and the connectors all look to be making a good connection. Any suggestions besides replacing the VR?

FWIW, I live in Colorado and until last week, we were having days where the high was in the 20's and the lows in single digits (which is colder than normal for us). Anyway, I had no issues with driving my 240 with 72 carbs (at least related to the cold ) After starting I let it idle around 2k for about a minute, and simply began to drive. I did make sure to keep the revs up when starting from a stop, but I had no bucking or other issues. Not sure what to recommend to you, but it is possible to get the SUs to run just fine in cold weather. I'd start with a rebuild as the ZTherapy video shows. If I had to guess, that will likely make things much better. Good luck!

Jeff, that's the exact part I ordered. The ordering process from JC Whitney isn't up to the standards of the better websites, but they were delivered as-ordered and I had no issues with them at all. I tried running them for a few minutes before I redid the wiring and didn't feel anything hot on the fuse tray, so I suppose it might be possible to avoid that if you have a clean wiring system. But as I said up top, I measured an extra 1 1/2 volts afterwards, and given that the power goes up by the square of the voltage, that worked out to be about 35% more power at the bulb, just due to the wiring! Good luck!

If you don't have an impact driver, use the "poor man's version" like I did: I put a #2 philips head in the stuck screw and tapped with a hammer. Don't go crazy as you might distort the housing. I think some of the problem comes from dissimilar metals having been together under pressure and temperature for a long time. That makes them want to stick to each other. The tapping helps break them loose. It's worked for me so far on 3 out of 4 carbs I've dissassembled. (The 4th didn't have any problems removing them.)

Last weekend I put a pair of H4 headlight conversions into my 73 240. It snowed most of the weekend and tonight was the first time I could take it out for a drive. Wow, what an improvement! I got them at JC Whitney (I had to stop snickering before I could get myself to actually place the order) and put new low and high beam relays and wiring in as well. I measured an extra 1.5 volts at the headlight contacts after rewiring which I'm sure also helps. I went with 100/55 bulbs, which are really sweet on low beam, and fantastic on high. They have a very flat and sharp cutoff on the top of the beam, a lot like modern HIDs. I live where there are very few street lights and lots of wildlife that likes to come out at night. I highly recommend this for anyone serious about driving at night outside of a major metropolitan area.

Brian, I have a 73 in which the PO had put a new fuse box in. Still, one of the clips was getting hot enough that I burned my finger on it. In the end, I took the box out, removed the clip (you can see the way the clip sticks out to hold itself in place, you can pretty easily pop it out) and soldered it. But even then the clip remained too warm. So I cleaned it with a pencil eraser and now it's not hot at all. Even though the box was relatively new, all that time at high temperature had oxidized the contacts a bit. Assuming that you don't have problems elsewhere you should be able to solve this. But be really patient, go slow, and make sure you disconnect the battery before you begin working on it. Good luck, Daniel

That's an interesting idea that I wasn't aware of, but I don't think I'm going to go that way. I'm on a tight budget, and if the money doesn't make the car faster/handle better, or more reliable/safer, then I'm not doing it right now.

Thanks for all the suggestions. I started last night with the Berryman's soak can along with tooth brush scrubbing and then rinsing in water followed by a final cleaning with spary carb cleaner. That seems to get almost all of it off, although the linkage isn't going to recover as well as the aluminum.

Carl, Thanks for checking the measurement on yours. Actually, the setup you described is how I received the car: 72 carbs with the adapters for the 73 aircleaner. But that was a pain to tune because the 73 aircleaner drops down lower and it's virtually impossible to get your hands on the mixture nuts. Also, the aircleaner has square air horns and the carbs have round inlets. So I bought an earlier aircleaner on eBay which is what you saw in the picture. Turns out they both take the same size airfilter which is just under 2" tall. So it may be that I just order one for the 73 - which goes against my instincts. I think I'll follow your suggestion and call MSA and see if they can check the height of the filters before I place the order. Thanks,

I just received a set of 4 screw roundtops that I bought on eBay. They had been sitting on the car unused since '82, and show it. My question is the what is the best way to clean them? The aluminum has the usual discoloration from oxidation which I assume is inside as well as outside. Also, the linkage is anything but shiny. I have a large can of Berryman's Chem-Dip for Carbs which I was thinking of letting them soak in once I break them down. Any other suggestions?

So if I am getting this correctly, the early aircleaners thru 72 used the thinner airfilter element and then switched to the thicker in '73?

I have what I think is an early 70's aircleaner assy I bought on eBay. (note the manual summer/winter valve) When I put it on, I took the air cleaner element out of the existing 73 assy and it fit perfectly. Later I ordered an new air filter for a 70-71 aircleaner from one of the many Texas online parts places. What came was about 2 3/8" tall which wouldn't fit inside either of my assy's. Turns out the one in there now is just under 2" tall. I've seen a few eBay auctions for filters for early 70's aircleaners and I've asked them to measure the height. All have come back at 2 3/8". So I'm confused about what I have. And more importantly, where do I get a new airfilter that will fit?

Interesting comment about the shifter knob. That is where the sound seems to originate, although mine is not wood but leather instead. I plan to change the bushings anyway as I'm sure after 30 years and 200k+ miles they need some help. That may result in less vibration of the shifter and hence less noise from the knob, or at least that's my thinking for the moment. I have a new rubber boot under the leather shifter boot. But you mentioned "three rubber pieces". What/where are the other 2? Thanks.

That should be long enough. By then I should (had better!) have a 5 speed in.

I see the parts in the Motorsport catalog, but it doesn't say what material they are made of. Any suggestions where to get brass?

On my 73 240 with 200k+ miles I still have the stock 4 speed. The second gear synchro is a bit worn and for the first few 1-2 shifts when cold I can feel the gears hitting a bit before they engage. I recently replaced the gear oil and things got better, but it's still noticeable. Once warm, the issue goes away. So my question is if it is better to shift slowly so that the revs can fall on their own and put less stress on the synchro, or shift faster so there is less slippage with the synchro? Hope this isn't too philosophical... :stupid:

Whenever I get over 5k revs at WOT on my 73 240 the shifter begins to vibrate enough to make a loud sort of buzzing noise. I recall someone saying that this was due to the shifter bushings being worn, but before I change them I wanted to hear what others thought. Daniel