For a while now, folks have been asking me to finish the page I did on this topic, on my website, but I figured a thread here would be easier to find, and seen more often. As a disclaimer.. This is not meant to be the end all and be all of block/prep and mods.. just what is done here at TSP. Others may have some other ideas. I will say, that I have never broken a block, from overstressing it, in a customer's engine. I broke one years ago, in my own race car, at the 540HP level, after many, many passes on the dragstrip... split it from the number 3 cam bearing, to the number 3 main. Part 1 Block ID and basic prep. Block casting number 67-76 All the BBB's have the casting number here. Here are the 455 numbers, since those are the most desired.. 1970/early 71 - 1231738 Late 71-Mid year 72- 1238861 Late 72-76 - 1241735 The blocks are typically reffered to with the last three digits of the casting number. "Blue Blocks"- Often on the board here, you will hear that term thrown around. In 1975 GM mandated that all engines were painted the same color, which was a medium blue. When someone says a "Blue block, they typically mean that they have one the later blocks, which were somewhat thicker in the cylinder walls and deck surfaces, due to a new mold being made around that time by the factory. It's thought that they added the material because the later low compression smog motors ran hotter, due to the tune up, but I beleive it was simply just the way they made the new mold. All of these blocks were 735 blocks, and they have 455 cast in them here.. It should be noted here that all blocks are subject the the issue of core shift, read the sticky on sonic checking blocks in this forum. Don't assume because you have a late block, that it's suitable for your build. Block VIN number The second digit of the VIN number tells you what year car the engine was installed in. There are several locations for the VIN number 738 casting, 1970.. 738 casting, early 1971 close up of a 70 VIN number It's overall location- Driver side, on the deck surface, between number 1 and 3 spark plugs 861 casting, late 71-mid 72 Under the Driver side cylinder head 735 casting mid 72-76 Stamped vertically on a machined surface of the block, just to the left of the timing cover, (while looking at the front of the block). Just above the oil pressure sender, on the front of the block. The first digit will always be a 4 as it was GM's code for the Buick Motor Division, the second digit is the last number of the year of the car it was installed it.. example "0" for 1970, 1 for 1971 ect.. Stamp codes Used to ID the particular model of the engine, within a given year. All BBB's have this stamped near the dipstick hole, on the Driver side deck surface. There are mulitple sources on the net to find these codes, but suffice it to say, anything that the second letter is "S" means it was originally a Stage 1 equipped engine. This particular example is the common 1970 Big car and Riv motor. The stamp can be anywhere in this area of the deck that was exposed by the heads, and is often corroded really badly, mis stamped, double stamped, or missing all together. Although a critical factor in determining an original STG 1 engine, for general hot rod engine building, I like to use the second digit of the VIN to ID the year of the block, because what cam the factory used in the early 70's means nothing if your building a hot rod motor. And this stamping just indicates the particulars of that engine model. Some will tell you that all "SS" 1970 motors had a 5/8 pickup tube and 5/8 oil passage to the pump in the block, but I have seen several that do not. Once again, be careful of assuming anything, when it comes to factory built stuff. Date Code A letter, indicating the month of the year, and one or two numbers, indicating the day of the month that this block was cast. Starts with an A for January, and goes thru M for December- in order.. but there was no "I", as it could be confused with the number 1. Located in two different spots- on 738 455's, and the early 400/430 it was here, on the passenger side of the front of the engine, next to the timing cover. On 861 71's and later blocks, it's in the lifter valley. That's all for block ID.. the next post in this thread will cover basic block inspection and prep for the machine shop.