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Sorry if there's already a thread for this but I recently bought a boat and pulled the engine out. The block casting numbers 3963512 A29-71 hi perf pass stamp and the heads are 3964291 steel rectangle port. The piston number is L2349 030 Can anyone tell me some more info on this engine? Is it desirable to the car world? I just want to build a boat engine, I rather this go to a car guy if it's worth something.
Your block number ID's as a 427/454 COPO block available between 1969-1971. According to the source info, it could be either a 2-bolt or 4-bolt main. Your block's date code (A29*71) indicates that it was cast January 29, 1971.
The heads are definitely keepers and the same ones used on the legendary LS6 engine. From the source info: 2.19" intake/1.88" exhaust valves, 108 cc chamber, & 325 cc intake port volume.
The piston is a forged (L) 454 (2349) model 0.030" over (030). I couldn't find any info as to valve reliefs or dome configuration.
Judging from the degreed balancer and the valley tray, I would suspect that someone down the line tried to build their own LS6 as the heads were only available from 1969-1970. On course, the next step is identifying the cam currently installed.
Engine identification
