Just about everyone that wants or needs a small block Chevy engine built is aware of the 3.75" stroke upgrade to make their 350 CID engine into a 383. It is a great way to add some torque for very little additional money. For years, before the appearance of the affordable racing connecting rods, the factory rods were used and there was very little problem. The blocks required some very minor clearancing and everything fit very nicely. Jump ahead several years and now $750 - $1000 American made connecting rods are being produced in China (and other cheap labor countries) and being sold here for $150 - $450. Just about everyone can afford them when doing an engine build and it is a wise choice. However, all of these rods are bulkier than their OEM counterparts and require a lot more block clearancing. Some rods are bigger than others and it seems that the H-Beam rods are the ones that require the most amount of material to be removed from the block. The area at the bottom of the cylinder closest to the cam is not a real problem as it is fairly far away from the water jacket but the area near the pan rail is another story. Depending on the year of block and the amount of core shift, there is a real danger of breaking through to the water jacket when doing the clearancing work. There is just not much material there. We have had to discard many blocks and it gets costly doing so. Our engine shop technicians are suggesting that we no longer use H-Beam rods in OEM blocks with 3.75" stroke or more. It is getting costly for us to keep finding good blocks. Sonic testing is not a good test here as the area in question does not provide a good parallel test area that is needed for an accurate thickness test. Most of the I-Beam rods are requiring about .050" less material to be removed and that seems to give us the amount of material thickness to maintain a good solid block that will not break through during machining and it most likely will not spring a leak in service. For those that are going to be making the horsepower that will require the larger H-Beam rod or the even bulkier aluminum rods, we are recommending that we use an aftermarket block such as the Dart Little M or the Motown block from World Products. Everything on those blocks are thicker and heavier and it is a much better base for a high horsepower engine. Remember, ALL OEM parts are designed for passenger car and truck use and were NEVER intended to be used in the applications that race engine builders use them for. Engineers at the factory get bonuses for cutting weight out of a part that will save the company money over a large production run so keep that in mind when making a decision on which parts to use.
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