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I posted the other day about sputtering at high speeds (100mph) and received some great suggestions. Thanks There seems to be an issue I just discovered, bubbling in the fuel line, I guess it is air. I orginally thought this to be vapor lock as I am in AZ and it is very hot. However the other day I took the car out and it began running poorly in seconds, well before vapor lock should have occured. I have included a photo it seems there may be air in the line and it is causing bubbles and I guess that is causing an inconsistant fuel flow. I am guessing I have a hole in a line or some loose connection that is causing air to be sucked into the fuel lines. Has anyone had an issue like this, or any suggestions. I do not see fuel line for sale for me to replace the current lines. In any case any insight would be appreciated. I guess this could be why the car begins to sputter as the fuel demand increases at the upper mph level. Thanks Glenn

New SU carburetors made in the U.K. specifically for Z's! The set comes with street-able needles installed. Easy to set up and tune! Check out our store! www.roundtopsfuelsystems.com

Hi everyone Here is my situation i bought a 72 240z That was sitting for many years i dropped and cleaned the fuel tank cleaned out the fuel lines put a new electric fuel pump new filters put 5 gals of 92 octan its now getting clean fuel to the carbs i purchased and installed carb rebuild kit i put new plugs and wires and it is getting spark i fired it up after a oil change and prepped the motor i had to play with the carbs for like a hour to start it had to use quick start to prim it and she ran great for 45 mins or so shut it off now she will not start anymore any ideas or things i should check P.s the carb next to the firewall sucks in a lot of air the the front not so much?

Here is the issue. I have a 260z that has headers and many of the original pollution control items have been removed. The carbs have been rebuilt by Z therapy - I have tuned them according to the video. The car is not running rich to the best of my knowledge. There is no air pump, with headers there is no exhaust gas tube, therefore no exhaust gases through the balance tube, the control valve is not hooked up. No water through the balance tube. The carbon canister purge valve has a crack in the lid, but otherwise seems to be intact. The car runs fine but after a strong acceleration the car wreaks of gas. Sometimes in the past to the point of eye stinging. What do I need to do to fix this. I have attached some photos to show areas missing their potential pollution control attachments. Thanks Z dude67

Hi guys. Wondering if there's any way someone here could help me out with finding a part I'm looking for. I'm currently converting my '73 240z to early SU carbs, and I need to find the long J hook linkage that comes off of the firewall bracket to the rest of the carb assembly. Linkage piece I need is shown in the photos I attached below. Does anyone have one of these or know where I can find one? ZTherapy told me to check around on the forums, and I'm not sure where to find one locally. Thanks in advance for your help! Courtney

Fully disassembled, inspected, and rebuilt to factory specifications set of early Datsun 240z 4-screw Hitachi SU Carburetors, E88 intake manifold, balance tube, heat shield, springs, linkage, linkage to the firewall and air filter housing with OEM Nissan air cleaner/filter. As an option, you may choose the customer K&N filter setup instead of the OEM orange filter setup, or have both for an additional $50. Domes and pistons are polished and bodies have been painted with high-temp Eastwood fuel-resistant paint and baked to cure. Also included is a Vacuum gauge installed on the balance tube to help diagnose engine problems and tune the carburetors This is a perfect kit for the 260z and 280z owners who want to upgrade to the reliable and high performance round-top carbs. Ready to bolt on and begin using! Professional installation is recommended as fine tuning may be required depending on the condition of your engine, gasoline used, and other variables not related to the carburetors. As with anything that is 43+ years old, these are not perfect but are great performers. This set is being sold as-is for $750, shipped anywhere in the USA. PayPal friendly and ready to ship within 1 business day of payment. More Pictures @ http://jarvas240z.blogspot.com/2015/10/240z-round-top-carburetor-kit-for-sale.html .

Hey y'all. Sorry, I don't know much about forum ettiquette as this is the first one I've joined.The guy said that everything under the hood was perfect, but after driving it for a week, I'm seeing that the carb intakes are leaking gas and the gaskets leading into the engine are wet with gas as well. I'm kind of a novice (at the Forum thing as well as owning a datsun/working on my car) so any pointers would be appreciated! I really want to do the car justice! - Josh Info: Original Engine - 90k miles Idle - 1500, sometimes dips down to lower 1000s Anything else that's relevant?

I pulled these off my 240z parts car and I am looking to rebuild them and put them on my 280z with a stroker motor. Any tips or concerns I should have and where to find a rebuild kit in general.I know they are in pretty rough shape but they are definitely rebuildable.

We have been working on rebuilding a 1973 240z which we recently purchased and came across another puzzle that I was hoping someone else had experience with. We recently got the car running and took it for a test drive. After driving about five miles we stopped for anoint half an hour and then took off again. Almost immediately the car would buck and shudder any time we tried to accelerate. For a short time it would idle but then shudder and die under acceleration. We ended up towing it home. My initial thought was that the fuel filter was bad. We added some gas to the tank (just in case) and put some Heet in the tank. We then pulled the fuel filter. It did not look dirty nor could I see a water layer. I cut the old fuel filter open just to be sure and it still appeared clean. While this was off I blew air through the gas line back to the tank to make sure it was not plugged and we could hear the air blowing through easily. We then installed the new fuel filter and then disconnected the fuel line on the carburetor side of the fuel pump. The fuel pump is a mechanical kind and it appears to be a new/newer pump. We turned the car over and lots of fuel came through. I dont have a pressure tester to do a real pressure check. We then reconnected everything and fired it up. It started up and ran pretty well. We then tuned the carburetors and found that they were not balanced hardly at all. We used an air flow meter and got them balanced and the idle set and the car was now sounding and idling much better than it had. So we took another test drive. The initial drive was around the neighborhood, low speeds and gently acceleration. The engine ran smoothly so we took it out to the main road. As soon as we began heavier acceleration the engine shuddered and bucked and promptly died. We let it sit for just a moment and it fired back up but would start to die under heavier load. We were able to drive it home carefully. We then did some checking with the engine running while parked and I could not get it to stumble or load up and die. I noticed that the fuel filter barely had any fuel in it. We shut the car off and the filter slowly filled up with fuel. We restarted the car and the fuel filter again ran to where there was barely any fuel in it but I still could not get the car to die. My guess is that either the fuel pump is not pumping at a high enough pressure which starves the engine under load or that something is plugging the fuel line from the tank, again starving the engine for fuel under load. I rechecked the new fuel filter and it is still clean. There is not sludge or grit in it at all. Any ideas would be appreciated.

Hi folks, I am a new Z owner (1972), and looking forward to refreshing/restoring this beautiful car. She currently runs OK, but could be better. I am, by no means, a great mechanic, but it appears that there are plenty of helpful folks in this forum. One of the previous owners of this car installed a CR PRO/FUEL adjustable pressure regulator downstream of the fuel pump, prior to the carbs. It is set on 4.5 (I assume this means 4.5 psi). I am not sure of the need for this fuel pressure regulator. I have read many complimentary comments on Z-Therapy's work in refurbishing the dual SUs, so I am planning to take that route. If the carbs are rebuilt/balanced, have any of you had the need for such a fuel pressure regulator? Should I be concerned about the fuel pump? I suppose I could easily remove the regulator to see how she runs. Any comments on this aftermarket piece would be appreciated. Thanks, Steve

I'm a new owner of a '71 240Z; I've posted on here a couple of times. While the car was in the process of restoration by the previous owner there were periods of long sitting and I am getting everything up to snuff. To help others help me here's what I've done so far: - Rebuilt transmission with new gaskets, bearings, synchronizer rings, and oil seals. Temporarily refilled with synthetic 75W-90 GL-5 (ouch; I know now), now has Red Line MT90. - Replaced clutch friction disc, pressure plate, throwout bearing, and slave cylinder - Replaced distributor cap, rotor, O-ring, breaker points, condenser, and ignition coil with OEM-spec Beck Arnley parts - Replaced plugs and wires with NGK BPR6ES and NGK wires, gapped per FSM specs - Dropped fuel tank and had it boiled at a local radiator shop; replaced fuel filter and am currently running a can of cleaner additive through with premium-grade fuel - Disassembled, cleaned, and rebuilt carburetors with the aid of the ZTherapy rebuild kit and video - Checked dwell, measured at 37 degrees, timed at 5 degrees (second notch from bottom on crank pulley when viewed from passenger side) with electronic multi-function light I'm now driving the car daily to and from work, ~40 miles round-trip. I do my best to keep the engine in the 3000 to 3500 RPM range while driving. The car starts well with the now-functional choke, but the choke/fuel nozzle assembly sticks and I'm planning to re-adjust and calibrate this weekend. I know that I've got an exhaust leak under the hood where the twin pipes meet the manifold; it's missing the flange gasket which I've ordered and will also be installing. The rear hatch also doesn't seal quite right and the original bad gas made quite the odor in the car, so I usually drive with my window down. Although the blower motor/switch don't work the control levers are functional and I can get forced air venting through the ducts into the cabin. This week as I've been driving I've noticed faint white smoke rising from the hood vents (the car has a 280 hood on it.) This morning while making a left turn I also noticed the smoke entering the cabin through the blower vents. I have not noticed smoke from the tail pipe while driving, neither while under load or idling at lights. When I got to work I popped the hood and took a look. I know that I have coolant seepage around the thermostat housing; I'm replacing the thermostat, both its gaskets, and both radiator hoses. I also saw that the frame was wet where the radiator filler neck hose rests near the front driver's side of the engine bay. Finally, there was faint smoke/steam coming from the valve cover breather and where its hose connects to the air cleaner box. Removing the hose cause condensation and puddling of what appears to be oil. I do get some hesitation/lag when starting from standing in first gear. Once it gets past that point the car will accelerate fine up to highway speeds through the other gears. Deceleration, whether in neutral or gear, often includes one or several backfires or pops, I believe from the tail pipe. If you've made it through all of that you now know what I do. I've been doing a lot of reading and searching through the forums, but I still have a few questions: - First and foremost, what should I be looking at for the above circumstances? - What is the "best/proper" way of setting float adjustment? I do believe that I am running too rich. The video shows the float horizontal at .55 in. while I've read on here about holding the lid vertical and tilting while blowing in the fuel inlet to measure. I sent Bruce an e-mail; maybe they've been busy but I haven't heard back. - What are common locations for vacuum leaks? The car has a later N33 intake manifold on it with the corresponding emissions-control balance tube. However, no air pump is installed and there aren't any devices installed on the balance tube. Perhaps related, the vacuum tap on the front carburetor is not there. The hole is not plugged, but the residual broken tap appears to be in place in the carb. Instead, a line runs from the manifold vacuum tap to a three-way join, then a line runs to the distributor advance. Does it make a difference which location vacuum is tapped from? Are there any good images showing definitively what needs to be plugged on the balance tube? - The engine no longer has the coolant line running around the back (firewall end) from the manifold on the driver side to the three-way joint on the passenger side. Instead, the line runs through the manifold and is then capped, with a corresponding cap at the 3-way joint. I am planning to remove the residual line and plug at the thermostat housing instead to eliminate the dead zone; are there any problems with not running coolant through the manifold? The carburetor spacers don't have cut-outs for water flow. As always, all help is much appreciated.

My duel SU round top 3 screw runs crappy and is backfiring through the exhaust when you pull your foot off the pedal(deceleration) what does this mean, does it mean it is running rich? Any help would be appreciated. It is also running rough and seems to want to stall. I just adjusted the carbs and float.I set the floats at 9/16 they do not suck full at that point but begin when the float starts to drop, I used the FSM for the carb sync. any ideas ZDUDE1967

I have a 260z with 3 screw dome carbs. It begins to sputter and hestate at speeds approaching 100 mph. It seems fine up until the 100 mark then it is as if it becomes fuel starved. Any idea what this could be. Thanks Glenn

I have a 260z with 3 screw carbs. It is running so rich that the fresh oil on a fresh rebuild is dirty and fuel smelling with only 2.5 hours of driveway idle time on it. Carbon fouled plugs, toxic exhaust. You get the picture. I spoke to Bruce the other day and was given some great hints. In any case I took the pistons out today to check the needle jet height and found that no matter which way you turn the mixture screw located under the carbs -all the way in either direction it seems my jet does not move. I have included some photos. I guess I am trying to understand what part of the jet is susposed to move. I assume it is the center bit, the part that is down about 3/16 below the bridge. Is this correct. Would I actually see visual movement of the jet if I crank the adjustment screw all the way in either direction. Thanks Glenn

My car smokes a blue fuel smelling exhaust. I am thinking of buying the z therapy rebuilt kit and trying my hand at doing it myself. Has anybody used this kit and what was your level of success.Is it easy to use and does it cover how to adjust the floats Thanks Glenn

Hey so I don't know that much about cars so don't kill me if this Q is dumb. I was wondering what the benefits of switching out my SUs with triple weber carbs. What are advantages and disadvantages. any help would be great thx.

After 2.5 weeks of waiting, my new carbs have arrived! I decided recently that I needed to kick start things with the Z and do something to get me excited about working on the Z again (although the sun coming out really helps lately), so I called up Ztherapy and ordered a new set of carbs and a new balance tube. Next week is dead week and finals the week after that, so it's likely that I won't be swapping anything till spring break. Until then I'll just have to enjoy looking at these beauties.

The DCOM series of weber carbs were the replacement carbs for the Weber DCOE production. The Italian Weber DCOE production lines ceased in the middle of the 1980's and these carbs were the next evolution.Weber didn't forsee though that the electronic fuel injection systems would replace carburetors. The DCOM has improved performance over the DCOE carbs and more lasting on/off use due to the perfected acceleration pump diaphragm and adjustable pump lever. DCOM carbs will bolt on any standard side draft weber 40 DCOE carburettor manifold and uses the same inner parts, namely jets,needles, seats and floats as the former DCOE carbs. I believe this information to be very accurate however I wouldn't like to be quoted on it haha. Hope this has been useful Matt

I am putting on headers and will need to remove the exhaust and carburetor manifold for the new gasket. I want to make the process as simple and successful as possible and want to be able to just bolt the carb manifold back on, start the car and go. Is there any special process for handling the carb manifold, such as storing with the carbs facing upright or any other thing I should know to make carb and manifold removal and re-install successful. Will I need to re-adjust the carbs after the go back on? G