Locate the engine block code. This series of seven to eight digits begins with a letter and is stamped directly on the engine. Look behind the distributor on the passenger side of the block if it is a six- cylinder GM motor. On a small block GM V8, it is stamped in front of the cylinder head on the passenger side. The good news about 348 and 409 blocks is there were more than 18 different Chevrolet W-engine factory blocks built from 1958 to 1965. The bad news is that most were built more than 50 years ago and are showing their age, and many original blocks have been rebuilt several times. On top of that, rebuildable 409 blocks are hard to find and getting more expensive all the time. Swimways pro chip island golf. Original 409s are highly coveted and a decent block often sells for about $5,000 while the 348s are much more abundant and often go for about $1,500 in rebuildable condition. If you’re restoring an Impala or another Chevy car or truck with a rebuildable block, you already have the foundation for your engine build. But if you’re looking for an engine to build, old iron blocks are not the only option. Companies, such as World Products and Bob Walla Racing, offer new aluminum blocks based on the original W. Certainly, if you’re considering a high-performance build of 550 hp or more, an aftermarket aluminum block provides far more strength and has many enhanced features that are covered in this chapter. Therefore, these blocks are a far more reliable and cost-effective alternative for a high-performance build. This Tech Tip is From the Full Book ““. For a comprehensive guide on this entire subject you can visit this link: SHARE THIS ARTICLE: Please feel free to share this post on Facebook / Twitter / Google+ or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://www.chevydiy.com/chevy-348-409-engine-block-guide/. If you opt for an original block, most dedicated W enthusiasts can find a useable one for building a 348 or 409, but it may take some time and patience. The trick is to know what you’re looking at when you do find one. And if you cannot find a sound OEM 348 or 409 block for your engine build, aluminum aftermarket blocks are available, and these blocks are ideal for a max-performance build. The first question W hunters typically ask is, “Just how many did they make?” As with block casting numbers (or any casting numbers for that matter), the information on just how many blocks were made by Chevrolet is incomplete. We do know, however, that production of the 348 was not shut down when the 409 began. Chevrolet continued making the 348 to use in trucks, going into 1965. In fact, because the 409 was introduced in early 1961, the 348 was offered to car and truck buyers for more model years than the 409. The 348 ran from 1958 through 1965 and the 409 was produced from 1961 through 1965, or seven years to four. Block Identification One of the quickest ways to spot a 348 or 409 block is by its front. W engines have the two water pump inlets to the block spread out across the front. The holes are located very close to the outside of the block and their inlets (with one side flattened) are closer in shape to a diamond than a circle or oval. They are located just above a freeze plug and use two bolts to mount the water pump on each hole. If the block being inspected still has the water pump attached, it’s easy to see that the centers of the two bolts holding the water pump to the block are on an angle, as opposed to being vertical. Chevrolet placed an “X” on the front of the block for the passenger 409 engines and the truck 348 engines, so if your engine has X in this location, it’s a 1962-or-newer model. The external physical differences between a 348 and 409 block are virtually nonexistent. Although some folks use the location of the dipstick to determine the engine size, the oil pans determine where the dipstick is located, not the blocks. Therefore, since the 348 and 409 oil pans are somewhat interchangeable, identifying a block using dipstick placement is not 100-percent foolproof. If the block has had one or both of the heads removed, checking the bore can provide solid clues. But as some blocks may have had work done to them in the past, bore size IDs are not always proof, either. Casting numbers are still the fastest and most accurate way to identify a block. Design Features The cast-iron W blocks distinctly differ from small- and big-block Chevys in a few areas. The first and most obvious is the water pump inlet hole locations in the block, which are spaced farther apart than on small- or big-blocks, and the openings are diamond shaped rather than round. The cylinder reliefs are the next identifying feature, which are cut into the piston bores as detailed earlier. Both the 348 and 409 were used in truck applications, and these engines had two relief cuts in the bore to reduce compression. As a general rule, those two cuts equal the 7.5:1 compression typically seen in a W engine for trucks.
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