the_journeyman

Just checking to see if anyone has some Mikuni carb jets laying around. I'm looking for mains around the 130-140 size, pilots in the mid-50s. Obviously, I'll need a set of six per size ~ Thanks! JM

Thanks for the input! I do have threaded ports in the manifold, but when I remove the hex nuts that are there, it's just metal underneath. It's like it's possible, but I'd have to drill underneath the nuts. Not something I'd want to do unless I had the manifold off the car so I could get all the shavings out. I'll just go with one of the other methods or the ear method. I got them close just going by RPM changes & smoothness. I'm not too impressed with whoever did the initial setup on these carbs. Each carb is running a 95 & 105 main rather than something matched & closer to 130. JM

I've searched three different forums and can't find an answer. I'm working on sync'ing or balance my triple Mikuni carbs. I've done this several times on motorcycles with just a vacuum gauge with great success. I know it's not a Unisyn or similar, but patience yields just as good results. The vacuum advance for the dizzy is connected to #1 carb. The middle carb doesn't have anything, and I can't get a vacuum reading on the port. Third carb, can't get a reading. I'm trying to connect to the same place the advance tube is connected to on the #1 carb, but I don't have the tall nipple like on the #1 carb. What am I doing wrong? Thanks! JM

Update after some fuel pressure changes: So, after dropping the fuel pressure to 2.5-3.0psi and driving the Z to work for ONE day (7.5 miles round trip) and keeping the RPMs up to help pull more fuel & cleaner through, my plugs are a brown-gray color. I had made a 35 mile trip with the fuel pressure running a 5.0-5.5psi to bring it home. The plugs were black, even after that trip. I'm sure the fuel system & carb cleaner could contribute to a lean mix, BUT this is a pretty drastic change considering 35 miles at freeway speeds didn't make ANY change in the appearance of the plugs, but a 7.5 mile trip of mixed driving post-FP adjustment made the plugs go from black to brown-gray. This tells me I am pretty lean, which is expected if I am running 95 & 105 mains. Another day or two of driving is in order to see what happens. I'll keep watch on the plugs & listen for ping/knock from the lean mixture. I think I am starting to have a good idea of why this car didn't run quite right. This possibly confims my theory that someone didn't understand the carbs were getting too much fuel pressure. They likely kept going leaner and leaner on the mains thinking that was the problem. Can any carb pros/specialists make any sense of my posting? Thanks! JM

Thanks! I'll check both out if/when I need some experience on my side! JM

I live in Waynesville, NC. Are there any good, reliable mechanics or shops that specialize in the 280Z? The nearest large city is Asheville, NC. I may find need for a thing or two I'm unable to undertake myself due to lack of space & tools. Thanks! JM

Oops. Duplicate.

Pics of things: Fuel pressure gauge & what was ID'd as the fuel filter. Lines go from the gauge through the banjos on the carbs and back to the valve with the red knob. The position of the red knob gives me about 2.5-3.0psi. I got an improvement on my plug readings after a short putter through the neighborhood. Vacuum gauge, line runs from 3rd carb to back of brake MC on fender side Overall shot of bay, seems really empty, pass. side Another overall shot, FI stuff is circled in red. Stuff goes in, nothing comes out, so that must be only FI stuff, and the chassis wiring moved Found this under the rear carpet, bet that bottle of inflator is past its expiry date Hope that helps! The vacuum advance is still hooked up, pulls of the 1st carb. If it is hooked up with the electronic ignition, is that good or bad? Can I just unhook and see what happens or will I damage something? JM

I'll get on that when I get home this afternoon. Since I'm running carbs, not FI, I'm assuming I would need a FPR for a model that was originally equipped with carbs? Possibly something like this: Holley FPR JM

Ok, I didn't realize the filter would be that large, but at least I know what it is and can check it's condition. So, I'm guessing that I should keep the return valve set where I'm getting the 3psi the Mikuni carbs want. I should probably check into a pressure regulator and do the fuel delivery right. I'll look at the wad of wires. Whoever changed the FI to carbs rolled the wires up and stuffed them in a heavy plastic bag. I can trace it ALL to one thick wire bundle coming from the driver's side of the firewall, near the bottom. I'll see what all of that stuff is. There are no wires running to the motor itself aside from the spark. Thanks for the input! Every little step helps! JM

Ok folks, hoping to not be a complete pest here, but as I look over this 1978 280Z I've got, I keep finding more and more questions. Bad part is it isn't things that would be covered in the FMS (I have a PDF of it) since it's non-original parts & prior modifications. Ignition stuff: Timing light is simple enough to use, never done it, but after reading the process on here, I won't have any trouble. However, does having the Crane XR700 electronic ignition change that any? I don't *think* I have a vacuum advance attached, but not 100% sure. I'll have to check. If not, is it needed with the electronic ignition? Fuel System Fuel pump clicks loudly, but seems to make good pressure (5psi according to gauge) and seems to supply plenty of fuel. Fuel tank is much newer than the car, so I'm assuming the pump was added with the tank. Fuel Pressure Gauge, I'm assuming has been added. It is mounted a line leaving a cylindrical thing about 3"-4" in diameter that tapers round on the bottom. It's near the passenger side fender, fuel line enters bottom, comes out top. What is that thing? Fuel return line has a valve (quarter-turn on/off kind like a petcock). Completely closed, fuel pressure is 5-5.5psi, completely open, gauge reads 0psi, but car still runs. Pressure comes up as you turn the valve. I have it set where the gauge reads 3psi (about half-way open) since the Mikunis want that pressure AFAIK. Brakes Vacuum line (assuming, coming off top of carb) coming from the 3rd mikuni connected to brake MC. It has a twist-type valve that you can vary from open to closed. Haven't messed with it, but what would its purpose be? Other Air horn & fog lights added, relays added for them too. That's probably a good thing since the horn has a compressor & lights are really bright. Bumper delete has been done, nothing really added except a little thin metal flange added to the rear for appearance purposes. Will it pass like that in NC or am I going to have to find a bumper? Old FI equipment still in engine bay, just wrapped up and zip tied to driver's side fender. Is this hurting anything? That's all for now. Thanks!

That's what I thought too, I just needed someone more knowledgeable to verify that was unusual. I'm going to try to locate an assortment of jets around the suggested factory settings and see what happens. Mikuni recommends just one turn out on the idle/pilot screw, but the car won't idle. That may be a result of the small mains, IIRC they have a trickle-down effect even if you're not on the main circuit. That may explain why the pilot jet is also so big (57.5 instead of 50) Too bad my jets from the bike carbs won't fit! Neither do I, but it is definitely blowing out, you feel it blast outward past your hand when you open the filler cap. It's opposite anything I've ever experienced. It does it both with the return line valve open or closed, a bit less when closed.

Ok, as I research more and more, I a link to Mikuni's site AND found a recommendation for stock settings with the chart. Chart So, it looks I've got to figure out if I've got 40s or 44s. My question NOW since Mikuni recommends a 140 main for a stock L28, what would lead someone to: 1) Run a much smaller jet (95 or 105) and 2) Mis-match jets in each carb with a 95 in side and a 105 in the other. I'm totally new to Zs, so I need a little help understanding them. Thanks for any help folks! JM

Yes, each carb has a 95 main on one side and a 105 on the other. From the front of the motor, the odd numbered cylinders are fed with 95s and the even numbered ones are fed with a 105. Plugs are black, pilot screws were mis-matched as well with no pattern do the number of turns. There were as few as 2 turns out, and as many as 4. All are currently at 2.75 turns out. When I open the gas cap it blows out pressurized air. The fuel pump clicks rather loudly too, don't know if that is normal, but it makes plenty of pressure. JM

Picked this car up, no knowledge of any motor mods other than Crane XR700 ignition module & Taylor plug wires. Plugs are black and a bit wet, which indicates running pretty rich. Heavy throttle application results in a really bad bog before it starts to accelerate. Of note - fuel tank is really pressurized after running for a bit, it goes PSHSHSHHH when you crack the cap open, and it's pressure coming out. According to the gauge mounted under the hood, it shows about 5lbs of pressure at idle. There is a on/off valve in the return line. In off position, it reads 5-5.5psi, as you open the valve in the return line, the pressure drops. Researching on here, I found that 3psi was preferred for the Mikuni setup. I partially opened the valve, and got the gauge to read about 3psi. It ran a little better, and didn't pressurize the tank as bad. Didn't solve the problem though I've got a couple carbed bikes, and I KNOW carbs can run better than what these are. I've even tuned Mikunis on bikes before, but this is new territory. Now, the current carb settings: Carb 1 Main Air1 - 200, Main Air2 - 200 Main1 - 95, Main2 - 105 Pilot1 - 57.5, Pilot2 - 57.5 Carb 2 Main Air1 - 200, Main Air2 - 200 Main1 - 95, Main2 - 105 Pilot1 - 57.5, Pilot2 - 57.5 Carb 3 Main Air1 - 200, Main Air2 - 200 Main1 - 95, Main2 - 105 Pilot1 - 57.5, Pilot2 - 57.5 I have located something that says 'factory' settings for the PHH carbs. Main Air - 175 Main - 150 Idle (pilot) 50 Accel Pump - 45 Where to start? Thanks for any help! JM