As i see it AGAIN the entire purpose for the 451 is ONLY a 440 in lighter block as per this thread and link.
The amount of weight savings between a 400 block and a 440 block percentage wise is in the noise by the time you get the engine together and in the car. I believe the true advantage is lower reciprocating mass and lighter rotating assembly
No one is building the 451 right
That's a pretty bold statement.
I'm working on a 451 now and I picked the stock 440 R/S ratio because I thought Chrysler knew something when they decided the rod length and stroke way back in 1958. The 451 combo has a light piston on a 440 crank and that will relieve some stress off the crank, which is nothing to sneeze at. Lighter reciprocating assy should save on some HP too.
So let’s break this down by the numbers. A 440 rod is 6.76” C-C. A 400 rod is 6.36” C-C. That’s a difference of .400”. The stroke length difference is 3.38” vs. 3.75” for the 440. That’s .375” difference in stroke. To keep all things equal at the 1.80 R/S ratio you would shorten the 400 rod ~.300” - as it is the 400 has a 1.88 R/S ratio so shortening the rod will make it like a 440. Or you can lengthen the 440 rod on the 3.75” stroke and get 1.88:1 R/S ratio like the 400. Some have argued that changing the ratio is meaningless but others try to split hairs and will do anything to get their desired number. I understand NASCAR guys go upwards 2.0. You can uncover a whole can of worms when dealing with R/S ratios, which is why I’m just sticking with the MoPar plan, but in reality is a R/S ratio difference of .1 even worth the time it took me to type this? The 451 / 440 rod combo parts were off the shelf so it’s not like hundreds of dollars were spent on custom orders.
Something else to think about. The ratio is irrelevant when manufacturers are creating bigger engines under the direction of marketing. Let’s take the 400 SBC. It probably has the worst R/S ratio ever created but they built it anyway. Bottom line: It was a 400 CI engine when people were into “bigger is better”. It had to pass the warranty period. And GM was not going to make a special tall block SBC just to satisfy the marketers.
Another observation: If you look at all the American V8 engines around the big design change in the 50’s you will note that they all were originally designed for around 1.80:1. Ford, Chevy, MoPar, AMC, Buick, Olds, Pontiac, Cadillac, etc... So, following this logic, when the cubic inch wars started to heat up, the most economical way to increase displacement was to stroke it. And again, rather than casting a special block to keep up with marketing every time someone wanted to add some inches, piston, rod and crank changes are the more economical solution (Chevy 427 to 454). Yes new blocks were cast to accommodate larger bores (i.e. 413 to 440 MoPar; 427 and 428 Ford) or very long strokes (i.e. 425 to 455 Olds) but many just went the crank rods and piston route (i.e. Ford 289 to 302; 352 to 390 - even the 428 has the same deck height as the 352).
