Hi Guys

I want to reduce my b310 Fuel consumption a little more since it is using little more fuel than i expect in short tours, Which Carburetor jets do i need to replace with smaller ones to adjust it ? I am sure it can be reduced more because it is having super lot of power on it, can go a big hill up with 3rd and forth gear unless you stop the car completely,

thanks
regards
sumith

It is the main jets, both primary and secondary.

However, usually the factory-fitted jets are just right for fuel economy. The gearing is the most important factor. A 5-speed B210 got 20% better fuel economy than a 4-speed (38 mpg vs 46 mpg).

Speed also matters: B310 test Observed fuel mileage (steady-state mpg) with A14, 5-speed, 3.7 final ratio
* 35 mph: 68 mpg
* 45 mph: 51 mpg
* 55 mph: 37 mpg

These factors will greatly decrease your fuel economy:
* Weight: Carrying unnecessary weight in the car
* Dragging brakes
* Choke not working correctly

Hi DD

Ok Right I got it,My Driving is economy as usual, i doubt i have factory sizes jets on it do you have an idea which size is for A12A engine Primary and secondary Jets for 1977 Model ?

thanks
regards
sumith

The mass of the car isn't important when cruising at constant speed but it sure is for windy roads or traffic.

http://datsun1200.com/modules/mediawi ... Carburetor_Specifications

has all the jet sizes for different engine and years

Hi Guys

Some B210 Models differ from year to year , I am using 75 main on my primary and don't know about secondary , still it will not give me more then 14KMPL on Long trips,on short trips it is very low about 10-11, i was running 80 Main Jet primary on my b210 it gave be 18 KMPL on Long and above 14 on short, what would be the possible cause do you guys thing, i am sure b310 engine is on good condition

thanks
regards
sumith

75 is way to small in my opinion try a size 96. If it using so much fuel with that jet size and it actually runs decent i would be looking at a stuck power valve. the power valve design is horrible on these carbs in my opinion they randomly get stuck in different positions.
I guess your power valve stays down which compensates for the small primary jet??

Take the carburetor top off and turn it over




This is the power valve actuator (rod), it has a spring. The hole by it is the vacuum signal, and is the only place in the top gasket which is critical.

* Check the rod to ensure it is not stuck (or sticky)

Hi Guys

OK thanks i will check that on saturday, is there any way that i can get an idea whether i am using correct size jets including main and air bleed jets ,are they labeled ? i saw a main jet labeled 5.5 does it mean it is size 55 etc ? because i don't have measuring tool,

thanks
regards
sumith

yes 5.5 means 55. You should never measure jets by sticking metal in them. They are precision and scratches can affect the flow rate.

B310 jets in most places (except USA) are
Main jet,
primary, A12: 96
primary, A14: 104
primary, A15: 100
secondary, A12: 150
secondary, A14: 150
secondary, A15: 145

Main jets are located here, by removing these screws