Whenever it comes to upgrading or replacing engines for those who want maximum power it seems it is always the bigger the more powerful, the better. So it goes with Chrysler motors especially when it comes to the vintage retro "Muscle Cars" of the 1960's and 1970's.
The "B" and "RB" series can be said to be the "Big Boys" or the "Big Blocks".
The basic designs of the "B" as well as the "RB" series of power plants are essentially the similar if not the same.
This means to a reasonably experienced automotive person with automotive repair skills, that a "RB" series engine can be installed in place of an "R" and vice verso. Take note that if an RB block is wider and taller than its cousin or sister.
If an RB block replaces a previous B block under the hood the mechanic in charge may well find that he or she will have to proceed with additional modifications to accommodate the increased size and girth of the newer replacement engine block. In addition for clearance needs special or different exhaust manifolds or headers may be required.
The question becomes if all B engine blocks - that is the Chrysler 350. 361, 383 and 400 - are of a similar design? It seems that this group and family are all pretty much laid out the same of the same designs. Two bolt main bearing caps are the distinguishing feature in this series. You can count on the essential designs and layout being very strong and durable. So durable in fact that Chrysler never entertained the need to enhance the product line, and upscale it with four-bolt blocks, even in their very high and highest performance versions. Basically you can be reassured that virtually all the parts and components, that is except the pistons themselves, among all the different displacement versions, are interchangeable with no modifications required. Well that is the theory at least. Welcome to the real world of cars, autos and automotive and classic 60's "Muscle Cars" enthusiasts. They are a strange and unique breed indeed.
What of the "RB" blocks? "RB" engine blocks share many similarities with the "R" series but they are not exactly identical, although more than similar. The main bearing journal diameters are the same as the "R"s. However you can count on this grouping of motors being overall larger than those of the "B" set. It is often noted that the cylinder bore diameters themselves are different among the different displacement engine varieties (413,426 and that of the massive 440) and that generally the smaller displacement in real life motoring on American roads and highways do not have a thick enough bore sleeve to accommodate the strain and work to be over-bored to accept pistons from the next larger displacement version. It can be said, for good effort and results, that you can count on the majority, if not the entire groupings, of the "RB" engines to have the same reliable, durable and racetrack proven two-bolt main bearings caps setup.
With your new and larger engine especially with the 1960's Chrysler and Mopar "Muscle Cars" of legend - be they 60's Plymouth "Road Runners" or Dodge "Super Bees" or all the way to the 1970 Mopar Challengers, Barracudas all the way to the 426 Hemi Cuda the thrill of speed on the highways and roadways of America as well is Canada is always there. On top of that you cannot have too big or too powerful motor and engine block.
