MOONSHINE HARLEY DAVIDSON X131

 

DESIGN CRITERIA

JAY ROBERTSON WENT TO DARIN MORGAN AND ASKED FOR A HEAD TO BE BUILT THAT WOULD OPERATE IN A RANGE UP TO 5500 RPM OR PRODUCE MAX POWER BY 5500 RPM. RUN ON PUMP GAS. BE ABLE TO BE DRIVEN ACROSS COUNTRY. AND OF COURSE, BE FAST.

IN THE END DARIN'S HEADS MADE PEAK POWER BY 5500 RPM BUT CONTINUED TO HOLD THAT POWER PAST 6200RPM. PEAK TORQUE CAME IN AT 3700 RPM. KEEPING THE DRIVABILITY OF THE BIKE. 

The First design heads had 1mm over intake valves with stock exhaust valves. Peak power was 144 hp and 150tq. Two cams were used. Star racing .585 and S&S .550. The dyno graphs were similar  with the different cam profiles.  Jamie at Moonshine Harley developed a  head and intake manifold with Frankenstein Engine Dynamics. This increases the intake port size  at the head from 1.9 inches diameter, 2.83 CA to 3.3 inch CA. Moving the intake air velocity of the 131 capping at 5800 rpm to well north of 7000 rpm. A game changer. The heads have the raw airflow cfm for 7000 rpm but the head port diameter at the intake is too small causing air to shear and cut off 1 valve at 5800 rpm. Choking the intake port.  The next step is to send the heads to be port matched to the new intake. The combustion chamber will not be modified.

Moonshine Harley Intake

Moonshine Harley Frankenstein Intake 3.3 CA vs Harley 2.83 CA

Darin Morgan intake port M8

Darin Morgan M8 Intake Port


Darin Morgan exhaust port M8

 Darin Morgan M8 Exhaust port

 

X131 Dyno graph Spec 1

PR4 COMBUSTION CHAMBER

THE PR4 COMBUSTION CHAMBER WAS THE IDEA  OF  CYLINDER HEAD EXPERT DARIN MORGAN.  PR4 STANDS FOR PRESSURE RECOVERY 4 VALVE

Darin Morgan building the first M8 PR4 combustion chambers.

DARIN MORGAN PR4 CHAMBER
ARIN MORGAN PR4 CHAMBER
ARIN MORGAN PR4 CHAMBER
ARIN MORGAN PR4 CHAMBER
ARIN MORGAN PR4 CHAMBER
STOCK M8 HEAD CHAMBER
Darin Morgan PR4 combustion chamber M8
Darin Morgan PR4 Combustion chamber M8
S &S camshaft sheet
Jordan riding x131
x131 after second rebuild
x131 timeslip 1st motor setup

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