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1966 - 1968 Corvette: Service Bulletin: Valve Hitting Top of Piston

Subject:   Valve Hitting Top of Piston
Model and Year:   1966 - 1968 Corvette with 427 CU. IN. 430 H.P. Engine
Source:  Chevrolet Dealer Service Technical Bulletin
Bulletin No:  68-T-17
Section:   VI
Date:    Jan. 11, 1968


Reports have been received of valve "float" at extreme high engine speeds, causing the exhaust valve to hit the top of the piston on 1966-68 Corvettes equipped with the special 427 cu. in. 430 h.p. engine (RPO L-88).  This condition was corrected in production, effective August 23, 1967, by reducing the installed valve spring height with a new valve spring assembly and two additional spring shims.

In service, the installed valve spring height can be reduced sufficiently to eliminate valve float by adding two (2) shims #3875916 under the existing production valve spring shim on all intake and exhaust valves.

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