030" (a very common over-bore size for almost any engine) to get to "fresh metal" and remove any wear patterns from the cylinder walls in the process. 030 oversize, which means the engine has been rebuilt at some point in time. there should be some stamping on the tops of the pistons, hopefully, which might be ".030" (or similar). ONE thing to be aware of, when buying ANY used short block/engine. The smaller stamp is which particular vehicle it resided in. Remember, it's the "machining code" which defines what the engine was built to go in and what other items were attached to it to make the completed engine assembly "hanging on the hook at the assembly plant". I also believe it could be either a 2-bolt or 4-bolt main block, depending upon how the main cap machining and such were done? Different strokes would mean different piston "compression height" for a constant "deck height" or compression ratio in the engine. Or if the main journals were the same size, a 327. It could make a 302 or 350 depending upon which crankshaft/piston combination was inside the block, of a 350 2bbl or a Corvette L82 for that matter, too. The -010 small block casting was pretty much common in the 1970s. This same configuration piston was also used in the 1986 Corvettes with aluminum cylinder heads (smaller combustion chambers and 9.5 to 1 compression ratio). with the rated 8.5 to 1 compression ratio and 76cc combustion chamber volume cylinder heads. Historically, "valve reliefs" might have started in the earlier 1960s, when camshaft lifts increased during the "high compression" era, BUT the piston in the 1971 Chevy 350 was what I term "4 valve cut-out, dished and beveled" piston in them. I have no doubt it would be a 1977 model year motor, given the three letters at the end of the "machining code". NTX5467 Edited Februby NTX5467 (see edit history) This will also have the 8 digit casting number nearby. In later years, the size of the engine was cast into the driver's side block skirt. for which there is no known decode for, that I'm aware of. If the stamp numbers on the pad do not match the indicated format, then the engine/block was a "replacement" item. The referrenced website has them in alphabetic order. In the GM parts books, you had to look through each model year's codes (cars and trucks had different books!) to find what you might be looking for. There are some others, too, which I believe have links on that website, which have the various numbers and codes for inline Chevy motors. Has "build codes" and casting numbers on their website.
#SMALL BLOCK CHEVY STAMPED NUMBERS ON FRONT OF ENGINE CODE#
I'm more familiar with small blocks than big blocks, but I suspect they are similar in where the date code casting is on the block. If you know the progression of what changes were made to the block castings and when, then you can tell a 1967 small block from a 1977 small block.
On small blocks, this is a casting section, about the size of my little finger nail, with the format "MDY". The DATE CODE for the block is on the block's rear extension, on the flat part, about 1/2 way between the rear intake manifold's seal and where the transmission mounting is. This would include, but not limited to, power rating, transmission choice, emissions specs, and which models of vehicles it could be in for a particular model year. The reason I'm terming the code "machining/build spec code" is that this defines when the engine was "machined", or built, at what plant, which day, and for what vehicle's specifications. The other numbers, smaller and possibly "deeper" stamps, would be very near the front edge of the pad itself, were the last segment of the VIN of the vehicle the engine was installed in at the assembly plant. The machining/build spec code would be in the larger numbers more toward the front of the cylinder head. it's what's IN the block which defines it rather than the block casting itself. "Generic" as it could just as easily have been built as a normal 350 V-8 or a 350 LT-1 engine. I believe the casting number would be a "generic" 4" bore block. Prior to 1970, the machining codes were "two place" for the V-8s. That lasted for several years afterward but was finally totally "away from that" by the earlier 1980s. The "three place" machining codes started in 1970, cars were "C" and trucks (including pickups) were "T".
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