Found this here...
Aerodynamics and flight dynamics of turbojet aircraft
BY T. I. LIGUM
Transport Press, Moscow, 1967
Engine installation in wings. When the engines are installed in the wing (between the upper and lower plankings), the total drag is reduced. In practice, however, the engine is fastened to the fiiselage (in double engine aircraft), while the air duct extends along the chord in the wing. This leads to a decrease in thrust as a result of a pressure loss in the duct, but in contrast an advantage is the almost "clear" wing (without secondary structures) which results. Engines arranged in this manner (close to the aircraft axis), if one of them fails this creates only a slight turning moment.
Of the disadvantages which result from this arrangement, let us point out the fact that it becomes impossible to make use of the thrust reversal due to the heat effects of the gas jet on the fuselage (for a double-engine aircraft) and the partial use of thrust reversal (for a four-engine arrangement) (see Chapter IX). The stream of exhaust gases creates substantial noise in the tail section of the fuselage and causes discomfort to the passengers seated in the rear. On the Tu-104 and the Tu-124 (Figure 57), the engines are located in the base of the wing, so that the greater part of the engine pod is hidden behind the wing. In the De Havilland Comet, however, the engines are fully-hidden in the wing (Figure 58). The engine's small size makes it possible to design its pods with quite small maximum cross-sections.
Engines located at the base of the wing create positive interference at the most complex aerodynamic point the joint between the low-hung wing and the fuselage. The effect of the Jetstream causes the formation of an "active fairing" here, i.e., an increase in the "regeneration" of the surrounding flow. This leads to a decrease in drag for the aircraft as a whole.
However, this engine arrangement requires an increase in the relative thickness of the airfoil profile, which causes a decrease in the aircraft's high-speed characteristics. The angle at which the engines are installed relative to the longitudinal axis is 3-5° in this arrangement. This inclination is necessary to guarantee that the engine exhaust flow does not hit the elevator unit.
It may help.