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Bob
Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4087
Experience:  Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
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Rebuilt Chevy 1500 305 engine with 350 heads, running hot with

Resolved Question:

Rebuilt Chevy 1500 305 engine with 350 heads, running hot with new 160 degree thermostat and running cold with no thermostat. Replaced water pump and fan clutch and 3 thermostats.
Submitted: 9 years ago.
Category: Chevy
Expert:  Bob replied 9 years ago.

Any chance you put the intake gaskets in backwards? They sure look the same, but if the ports for circulation are not open, that is exactly what they will do. I know how easy it is to do, because I have been there and done that. GM issued a bulletin on it years ago. Will send you a copy of part of it below. Thanks


 


#90-T-02: CORRECT INTAKE MANIFOLD GASKET INSTALLATION - (May 16, 1989)



MODELS: 1987-90 LIGHT DUTY TRUCKS WITH 4.3L, 5.0L, 5.7L TBI FUEL INJECTED EN- GINES (VIN CODES Z, H, AND K)


 


This bulletin is for informational purposes only, and should be used as a guideline if it becomes necessary to replace the intake manifold gaskets on 4.3L, 5.0L and 5.7L TBI engines. With the introduction of TBI engines, a change was made to the intake manifold gasket by adding a restrictor plate to the rear coolant passage of the gasket in order to direct coolant to flow from the front of the intake manifold, under the TBI section of the manifold (heats TBI to prevent throttle plate icing) and exit out of the heater hose pipe at the rear of the manifold (See Figure 1). Anytime it becomes necessary to replace the intake manifold gasket, it is essential that the gaskets be properly installed. If the gasket is installed backwards i.e., with the restrictor plate at the front of the engine, the engine will overheat. When diagnosing overheat conditions, the proper installation of the gasket can be checked without removing the manifold. Both the 4.3L, 5.0L, and 5.7L gaskets have metal locator tabs that can be seen sticking out from between the manifold and the cylinder head. When installed correctly, the tab on the 4.3L will be to the rear of the engine and the tab for the 5.0L and 5.7L engine will be to the front of the engine (sorry the pciture has been deleted long ago.)

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