The aim of this work is to study the effect of clearance, on the metallurgical aspects of diffusion rate and mechanical properties of the brazing joint using two types of Silicon-Aluminum filler metal alloys on the commercially pure aluminum base metal. The brazing process experiments done by joining Al-alloys (1100) type by a brazing process using (4043, 4047) filler metals at 600-650oC. Two types of joint accomplished, inclined and curvature design. To indicate the brazing joint performance the specimens tested for single shear tensile test and metallurgical testing using optical and scanning electron microscope assisted with energy dispersive detector. Diffusion rate results according to joint clearance and brazing time accomplished using optical microscope images for joints cross sections and data gained with assisting of ImageJ® software. The joint sections analyzed using EDS detector and X-Ray analysis to observe the produced phases. The major phases of brazed joints using 4047 filler alloy gives (Al, Fe3Si, Al 0.3Fe3Si0.7) and (Al 0.3Fe3Si0.7) for the 4043 filler alloy. The two filler alloys (5 and 12%Si) had equivalent tensile strength of 176 and 145MPa respectively, therefore the maximum joint efficiencies are 172% for AL5%Si filler alloy and 142% for AL12%Si filler alloy which mean that the tensile strength of the brazed joint had values greater than 100%.