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When purchasing a collectible muscle car or any collectable vehicle one of the very first things that should be examined of course is the engine. The engine block should have a casting number and casting date codes that align or match the build date of the car. Casting dates should always precede the build date of the car. If the casting date is after the build date of the car which is found on the trim tag or cowl tag of the car it is incorrect and consequently devalues the vehicle.


When purchasing an engine block seperate from a vehicle always look to see if any of the cylinder walls have been sleeved. Look for obvious signs the block has been decked or line bored.

In high performance applications look to see if the block has been converted from a 2 bolt to a 4 bolt main. Optional oil cooler tapped hole in side of block. There is no way to tell without removing the oil pan, something most people would not do if the engine is in the car. However on a Chevrolet factory 4 bolt main big block ( 396, 427, 454 )  there is an additional drilled and tapped oil cooler passage in front of the oil sending unit on the driver side rear of the block. The 3855962 blocks were only produced as 4 bolt mains all other high performance Chevrolet blocks were produced as both 2 and 4 bolt main applications. The Chevrolet engine blocks 1965 through 1971 that are most frequently converted are 3855961, 3869942, 3902406, 3904351, 3916321, 3916323, 3935439, 3935440, 3955270, 3955272, 3963512, and 3969854.

On small block Chevyís it is a little more difficult to tell if the conversion has been made by a skilled machinist. In fact it may be undetectable.
The only sure fire way to tell if the block is an original high performance block is if it has never been line bored. Be careful now, we are not saying if the block has been line bored it is a conversion. There are numerous reasons a block may have been line bored. If it hasnít been and it is a 4 bolt main it is for sure an authentic four bolt main.
Chevrolet small blocks 1969 through 1973 4 bolt mains that are most frequently converted are. 3932386, 3932388, 3956618, and 3970010

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