240260280z

Put the low pressure fuel pump near the tank so that it primes by gravity and so that it pushes the fuel. You can put a filter between the tank and pump to protect the pump and carbs. The carbs have built-in filters that should catch bits if your pump starts shedding impeller metal/coatings. A regulator near the carbs and feeding them ~3.5 to 4 psi (measured at the carb) is required. Cap off and seal the head where the mechanical pump was removed. Do not use a high pressure fuel injection pump unless you have a good fuel pressure regulator with a bypass outlet for feeding the return line. An unused power lead in the harness runs from the fuse box area to the fuel sender area. You can use a 78 280z oil pressure switch and a relay to control the pump operation safely.

efi overview: http://atlanticz.ca/zclub/techtips/efisystem/overview.html

I am exploring Weber carbs and decided to try to simplify and present their functioning so that others can quickly grasp the basic concepts. To do this, I decided to make a fictional path of design that Mr.Weber, may or may not have traveled. I will provide further details for operation and maintenance in future posts, however this first post is a very simplified introduction. Blue The Ideal The simplest carburetor design that comes to mind would be a tube to flow air with a source of gasoline spraying in the middle of the tube. This would provide even distribution and symmetrical mixing at the highest velocity point of the tube. Approaching the Ideal: The Main Circuit The Weber carb commonly used on Datsuns is basically just a tube with a fuel nozzle in the mid-stream of the air path. Unfortunately another part was required.... the Throttle Valve. To control the amount of fuel and air drawn into the engine a throttle valve was added. Its location was chosen to be downstream from the fuel nozzle as the manifold vacuum on the motor side of this valve would otherwise suck the fuel from the fuel nozzle when the throttle valve was closed. The main drawback of the throttle valve location being down stream is that it still blocks the air flow when open and, fuel sprays over it and can also be deposited on it. In addition to a simple tube with a fuel nozzle design, Weber shaped the tube so that it was narrowest where the fuel was drawn into the air stream by using the Venturi principal. This promoted fuel draw and fuel distribution. It is interesting to note this simple tube and nozzle design is nearly identical to a modern high performance fuel injected individual throttle body (ITB) manifold architecture. Reality and The First Corrective Actions: Adding the Idle Circuit and the Emulsion Tube Unfortunately for Mr. Weber, the above design was only marginally optimal for middle to wide open throttle and it failed completely at idle. Here are the main problems that he faced: At lowest rpms (Idling) when the throttle valve was nearly closed, there is not enough air flow over the main nozzle to draw fuel. (Lean) At higher rpms when the throttle valve was moderately to fully opened, the air fuel mixture became too rich as too much fuel was drawn from the main nozzle. (Rich) Weber was not beaten as the fundamental design worked in principal and could be modified to work. In fact the above design is actually the so-called “main circuit” of a Weber carb. Onward: The way Weber addressed these two problems of fuel flow at both ends of the RPM spectrum was: To address idling lean, Weber knew that the main nozzle was no where near the high velocity air flow so he added a new and totally separate second so-called “circuit”: the idle circuit. Basically he added a needle valve on the high vacuum downstream side of the throttle valve. This needle valve independently controls the amount of pre-mixed fuel and air (mixed upstream and not shown for simplicity) to flow past the throttle valve and feed the engine when the throttle valve is nearly closed (and the main circuit was not functioning due to low air flow). The simple one circuit carburetor now becomes a two circuit (Main and Idle) To address the need to lean the mixture in the main circuit as the throttle valve approached "Wide Open Throttle valve" (WOT), he added a “fuel/air mixing tower” with holes in it called an “emulsion tube”. Air and Fuel mixing took place in and around this tower before the fuel was drawn out of the main nozzle. Fuel entered the tower at the bottom of a well and air entered from the top. As the fuel demand increased approaching WOT, the fuel level in the tower& well lowered and in turn exposed more air holes thus mixing more air with the fuel. This ultimately leaned the mixture (as required) in the main circuit as more airflow through the carb occurred. Emulsion Tube Weber now had a 2 circuit carb design: One being the idle circuit and the second being the main circuit…. But how to switch from one to the other slowly and quickly? Dealing with the Transitions: Adding the Progression Circuit and the Acceleration Circuit. The Progression Circuit (for slow transitions from Idle to Main): Weber found that, as the throttle valve slowly opened, when transitioning from the idle circuit to the main circuit, the air flow required to activate the main circuit did not occur quick enough. This delay in the main circuit starting caused a lean spot between idle and main. The solution used by Weber was to simply add more fuel holes near the throttle valve. These holes were drilled upstream of the idle needle valve port. As the throttle valve opened, it exposed each successive hole to the manifold vacuum. In turn, (due to high velocity air and manifold vacuum) it would draw more mixed air/fuel from each progression hole. For economy, the source for air fuel Weber used was the idle circuit. The Accelerator Pump Circuit (for fast transitions from Idle to Main): Weber found that if the throttle valve opened quickly (when transitioning from the idle circuit to the main circuit) the progression circuit above did not have enough time to operate as the airflow suddenly was across the whole carb throat rather than up near the roof and progression holes. This sudden bust of air and delay in the main circuit starting caused a lean spot between idle and main. The solution used by Weber was to add more fuel by using a one-shot-squirt-gun-like pump that was activated on a quick throttle opening (hammering the gas pedal). The design also had a clever feature where slow throttle valve openings did not squirt additional fuel (to be shown in more detail in subsequent posts). Summary: - A Weber side draft carb used on many Datsuns has two independent "circuits": The Idle Circuit and Main Circuit). - A so-called Progression circuit is used to aid in slow rpm transitions from Idle Circuit to Main Circuit. - A so-called Acceleration circuit is used to aid in fast rpm transitions from Idle Circuit to Main Circuit.

Also a moral application of "Give Caesar what is Caesar's" falls into this situation.

Today: Drove by a cellphone in the middle of a T-Junction in our subdivison. Stopped, on the way back to have a closer look. It was not in bad shape and has been run over but just scratches on the outside of the clam shell. Put the run-over battery (that was on the road 3' away) in the phone, made a few calls to the last dialed numbers with no answer...and later when the owner called back, hand delivered to a neighbour ~ 400m away... even went back and found the battery cover. The guy's wife had entered the house, looked on their home phone and asked why her husband had dialed the house 3 times from his cell when she knew he was working in the garage. FYI:It was a Samsung

I saw that on craigslist or ebay last week... beauty. Congrats!

Yeah it seems like if you wait for a year to cycle, and watch the weely sales flyer, you can get most important tools at canadian tire for 45% to 65% off (ratchet sets, wrench sets, screwdriver sets, bit sets, power tools, torque wrenches, etc. but only princess auto has the roll-up-the-rim tool

Interesting. We have a few z's for sale here in Halifax, Nova Scotia, Canada....very close to Europe by sea (in fact there is a large autoport here). If any Europeans want nice z's pm me or my buddy Ross. Some examples of cars we have now: http://zsportcanada.com/listings/view/Datsun/240Z/81/ http://zsportcanada.com/listings/view/Datsun/280Z/77/ http://zsportcanada.com/listings/view/Datsun/280z/70/ Here is a Z we sold at the Autoport:

they all seem low... here are a few "gottchas" that get most first timers (including me): did you remove all 6 plugs before starting did you open throttle valve for each test did you crank engine over a few times for each test is your battery strong enough to crank the same is the test gauge calibrated or cross-calibrated are the valves seating well (check valve lash)

www.canadiantire.ca www.princessauto.ca

Late to the thread but rather than post a vid here to degrade the site, look up "ladysitter" on you tube.

Where are you in NJ? I am in Bridgewater at 287/22 if you ever need a hand.

I read it messes the threads if you don't un-stake them. If you have a dremel with a cutting disk it is not so bad. Use the 280zx nuts to replace them. No staking required. btw to respond to a query above. I have a hammer drill. I used it to drill pilot holes prior to fastening spikes in concrete. I may have used it on a vehicle once as an experiment.

Dealing with the public is always the same for any business....and the public is the public.Having a knowledgeable person, a "filler" person,or an automated system is the point raised in this thread. To me it seems that having no-expert-guidance at front end of the business is not in the spirit of business nor in the best interests of the customer. It is clear from this thread alone that MSA will trump VB/BD by anyone who reads it. I guess if the VB guy wanted to go the next step he could go offshore and have some poor underpaid, language-challenged, night shift worker try to do the job .... but other businesses have tried that and backed away following the problems with this cost-saving risk. After a while people start to open their eyes and see the crap....but sadly not enough.... they took the blue pill. However, the VB/BD owner could also assume that his customers are experts and therefore no guidance is required. If it was my business, I would make each employee buy an old Z, MG , etc. and restore it with parts at cost.

My understanding is that one should run the hose from the back of the head to the thermostat housing for best circulation when the head is getting hot but the thermostat has not opened.

MacDonald's staff? I wonder where the guy studied business? I can think of a few places with such business practices.

I agree with ignition module. Heat kills them over time. You can verify by watching the tach the next time it fails. If the needle falls faster than the engine revs die when coasting then it is an ignition problem. For a fix, I recommend this rather than buying a new module: http://atlanticz.ca/zclub/techtips/distributor/index.html

In the front is best and having the control near the ebrake makes for an ergonomic racing set up. Have fun!

[h=2]Brake Line Drawings 1972 to 1978 from FSM's[/h]

It is in the photo I posted (blury) but it is the right most block that the lines go through before they hit the "T".

Phred, Before laying down $300 do more research. I recently was web researching a mix-up in a part in a Precision kit and I do recall a post about Precision supplying MSA, VB and Nissan. I thought it strange but it may be worth checking out...especially these days with monopolies, buy-outs, closings and diminishing competition. Could have been on Hybrid or Zcar or Classic or another Z forum.

Excellent question. Unfortunately I do not have the associated data for the configuration of the test bed... 6,4,2,1 paired webers? 2or 3SU's? I don't know. However the data was compiled from a renowned performance investigator named David Vizard so it was proven somewhere. Given this,the only safe assumptions that we can make is that there are differential differences between geometries and the absolute performance gains (according to Norm's drag strip HP improvements) can be extrapolated to be in the order of magnitude of the drawing above.