B Block or RB Block for 500 ci build

[Bruce J]

I just started a stroker project on a 1975 400 block using a 440 source 470 stroker kit. After chatting with a few engine builders here are my 2 cents. The 400 block is stronger and will allow for slightly easier header clearance but if you go with TTI that doesn't really matter because they all fit fine. My 470 combo will allow for lots of street use without overheating issues, piston slap, etc., which is something to consider. The main problem with a low deck would be the intake options. If you just want a single 4bbl there are lots of options, but if you want to get into some "cooler" stuff like 2-4bbl, cross ram, or whatever the choices are limited. The engine builder im using has done quite a few low decks and actually competed in the engine masters competition around 10 times so I trust him when he says dont go over the 470ci kit on the low deck for regular street use. my original plan was a 500 or 512 because i simply liked the sound of over 500ci! but in reality, he said to save those ci for the RB blocks.

I agree. I was thinking about building a 500+ motor but came to the same conclusion just doing a lot of reading and from my past experience.

 

[BSB67]

Yes in a street engine either will be fine, In more of a race orientated does it really matter? I think if you have a combo that’ll blow out a RB block, a B block doesn’t stand much of a chance either. Looking for input from everyone on that.

Everything else being equal, the shorter cylinder walls in a 400 will be more rigid, holding shape better and less likely to fail. The lighter pistons and rods will be a bit easier on the bottom end. But every casting is different and its singular weak link is what will fail first. You simply cannot say with certainty which block will fail first or why. You're just stacking the deck in your favor with a 400 block