Mikuni PHH 40 jetting on Datsun 1600

Hey guys just after some advice of jetting sizes. Recently my brother scored some 40mm Mikuni off a Toyota 2T-Gs engine. On initial inspection the look in good cond with centre pull linkages still attached, plan is to use these with his existing throttle cable.

 

The Datto has a freshly rebuilt fairly standard L20b engine, 1mm over bore, SSS cam, points dizzy with working vac advance, comp ratio is about 10:1.

 

The phh40 carbs have the following: They are type S4, they are not the anti pollution type YAY! Current jetting is 52.5 pilots, 200 main air, 135 main jet, #8 jet block. These look to be stock 18R-Gs jetting combo except the Toyota pilot jet is 63.8

 

Sound like a good starting point? BTW the car is driven out of melb 800m above sea level.

 

Cheers

Whack em on.

In a Datto you have room for some trumpets, fit these, about 50 mm, go for a larg filter box type thingy, not four foam socks, they muck up airflow.

The 2TG is a 1600

If so the carbs will prob need next size up main jet, if fitting to a L20B

A L18 should be fine.

Run an Oxy sniffer on wide band, well up the exhaust, do some under load pulls, the sensor readouts will be all over the place, but you are looking for averages of 14:1

 

Being 40's, you will get very good airflow speed into motor, and good consistent atomisation of fuel in the air.

Thanks Jason. We have some 50mm trumpets, phenolic spacers, a long runner intake and we're going to copy the roadster style air box but will have two oval K&N filters sandwiched together allowing enough room and flow for the trumpets.

 

Will throw the wide band on and see how it goes. It's his daily driver and has been that way for 20yrs, so just looking for something nice to drive.

 

Cheers 

Whack em on.

In a Datto you have room for some trumpets, fit these, about 50 mm, go for a larg filter box type thingy, not four foam socks, they muck up airflow.

The 2TG is a 1600

If so the carbs will prob need next size up main jet, if fitting to a L20B

A L18 should be fine.

Run an Oxy sniffer on wide band, well up the exhaust, do some under load pulls, the sensor readouts will be all over the place, but you are looking for averages of 14:1

 

Being 40's, you will get very good airflow speed into motor, and good consistent atomisation of fuel in the air.

14 .1 a/f/m wont make pwr , ping its nuts of burn out plugs, burn out exhaust valves. good luck running this afm ratio

14 .1 a/f/m wont make pwr , ping its nuts of burn out plugs, burn out exhaust valves. good luck running this afm ratio

try 12s its a datsun remember//??

try 12s its a datsun remember//??

12.5 afm full throttle conservative , 14.1 is effen lean might produce good power but not for long, perfect air flow to fuel ratio correct if im wrong is 14.7.11 in all altitudes , but are you gonna jump outa car every time the weather changes an change the jetting size? I dont think so go on the richer side of the afm ratio, or am I wrong I would an do , lean out no good .

Thanks Daniel will do.

Thanks Daniel will do.

No seriouse Gareth, lean is good makes great power, but go too lean an the heat in the combustion chamber becomes so high and the pressure that it can cause pre detionation and you most likely wont hear it before damage has occured, from my exerience watching fuel mixture ratios on dynos was full;; noise 12.7,1  12.5.1 AFM ratio which is on the slightly richer side of leaning out, hardest part is obtaining that afm cosistently

No seriouse Gareth, lean is good makes great power, but go too lean an the heat in the combustion chamber becomes so high and the pressure that it can cause pre detionation and you most likely wont hear it before damage has occured, from my exerience watching fuel mixture ratios on dynos was full;; noise 12.7,1  12.5.1 AFM ratio which is on the slightly richer side of leaning out, hardest part is obtaining that afm cosistently

we have 3 go karts 100s yamahas, have wide band 4 wire exhaust temp gas sensors measures oxygen content in exhaust through tempature levels, I know 2 strokes are different to 4 strokes but as the day cools off and the oxygen content in the atmosphere inceases so does the power output of the engine too the point that it produces so much power through the heat increase in the combustion chamber due to the high level of oxygen to fuel ratio it melts itself down, trust me stay on the richer side of making full power at a lean point

 

We have a hand held wide band air fuel logger. I used that when setting up the FCR's on my car, I ended up with ratio's in the 12.5-13.5:1 region and 11ish when the accel pumps kick in.

 

Will probably try for around low 13's to begin with, it's a neat little road car that won't go above 6,000rpm.

 

Thanks again