Everything you've ever wanted to know about blocks and more...
Written by Brandon Nicholas in 2003.
Copyright
www.440source.com
If you haven't read our page on
An explanation of Chrysler's part and casting number system, be sure to check it out also.
Blocks are one of the most misunderstood aspects of building a big block Mopar engine. Never has there been more misinformation, propaganda and rumors floating around. In the many years we have been involved with the big block Mopar engine, we have seen and owned many many hundreds of used core engines. We have used this opportunity to try and keep records as much as possible as to different advantages and disadvantages that various blocks offer. All the facts listed below are the result of our
In the many years we have been involved with the big block Mopar engine, we have seen and owned many many hundreds of used core engines. We have used this opportunity to try and keep records as much as possible as to different advantages and disadvantages that various blocks offer. All the facts listed below are the result of our independently testing, measuring, sonic checking or otherwise gathering information directly from original sources: either the blocks themselves or the original factory drawings (blueprints) that Chrysler used to manufacture the blocks. This eliminates all chance of secondhand information, rumors, marketing or sales talk, etc. Hopefully this page will help hobbyists, restoration experts, and racers decide which choice of block is best for them.
First, let us address the biggest myth of all:
For many years it was thought that late model blocks were thin wall and should not be bored more than .030 over.
On page 198 of the Mopar engines manual, (the 8th edition) in the "B-RB Engines (block) section, it states: "The 1976-1977-1978 blocks for the 400 and 440 are a thin wall casting design. As such they shouldn't be overbored more then .020." This quote can now be found on page 58 of the new "Big Block B/RB Engines book from Mopar Perfomance, part # P4876825
Two pages later, (pg. 200) under "Boring and milling specifications," the manual states: "...The newer blocks (1975-1978) should only be bored .030" max., because they are thin wall castings. This quote can now be found on page 64 of the new "Big Block B/RB Engines book from Mopar Perfomance, part # P4876825
Then, in the May '98 issue of Mopar Performance
Are the thinwall blocks from 76-78, or are they from 73-78? Can you bore them .030, or is .020 the maximum? We will answer all these questions once and for all based on scientific fact. The purpose of citing these books and articles is not to make Chrysler/Mopar Performance look bad. As racers and hobbyists, we are grateful for the resources and aftermarket parts that Chrysler makes available. However, it does demonstrate how even someone who does their research could be easily confused. So, it is to the benefit of everyone involved to help spread information which is known to be true, even if goes against popular thinking.
So what is the truth? Get ready for this.
There is no such thing as thinwall blocks. They DO NOT exist.
We have sonic checked over 50 blocks, and have found absolutely no evidence that later model blocks have cylinder walls that are any thinner.
You need to go to 440 source and read up on what they have found with the blocks and what Andy found with the blocks.
There are no thin wall blocks.
