Just wanted to know the pros and cons of building a similar size stroker (512ci), but using 440 as opposed to a 400 or vice versa.

Not having any parts on the shelf to influence the build and cost is equal for either.

If both engines had the same stroke and same rod length the 400 would be better even if the bore was the same. The lower deck height means the pistons are shorter and lighter. The 400 also has a smaller main journal diameter so the bearing surface speed is lower for the same given rpm compared to a 440. A 400 based stroker would also be a bit narrower and easier to fit in an engine bay but that probably only matters for A-bodies.

I've head on a 400 based motor when you get to the 500" mark the pistons have very short compression height which can sacrifice durability.

The rb platform with the 10.72 deck hight is perfect for a 500" motor. And can't be much heavier

Don't forget the 400 is also 60+ lbs lighter than the RB, I have a 440 crank in my numbers matching '72 road runner and a 451" 12;1 compression 451 as a back up motor for my '70 Challenger that has been 9.60. That being said a business associate of mine needed a 400 short block gone (as in "FREE") after sitting around a few years since it was replaced with a 440 in his sons Charger, just pulled this thing down and it has never been apart, bearing match the date code of the block and being a '73 block should be a good candidate for a 512" stroker motor on pump gas for a street /strip car or back up to the back up for the race car..

Not true.
You can get into a rather short piston height (1.12 offered as a shelf stock piston)if you want to, but 1.32 used in a 512 build is not short by any means, just in comparison to boat anchor stock type 440 pistons. Look at the deck height and compression height on a lot of BBC stroker combos for a comparison of what works. The other thing, and most important when building a lot of power, is the strength of the 400 block. Much better than a 440.

^^^^^^yep,^^^^

Better main bearing choices for the RB block and a lot more intake manifold choices for the RB block. The 400 block is a bit smaller package and the 400 block might be stronger. Either one works just fine. There are usually better header choices for the RB block so you might want to look into that but it will depend on which head you use and which chassis.

Everything being the same which would make the most hp being a max effort motor...I'm stuck at the same cross road for my next motor ..well 2 cross roads lol ...but thinking b or rb block

It is easier to make more power with the RB block since you have more intake manifold choices.

I have a 499,512,540 low decks,wouldnt run anything else

It depends on what horsepower level you are building. What Intake manifolds and what headers will fit your car, as what heads you are going to put on it.

First the 400 is a little stronger, and the rotating weight will be slightly lower, so for a all out engine it is the best choice.

If you want to run a crossram for example, you might find intakes are hard to come up with.

If it has a head with a raised exhaust port, 440 and 400 blocks have a little difference height, couple that with aftermarket cylinder head heights and you may need custom headers.

Also any HP level over 650 HP stock blocks can be a little weak, aftermarket blocks are hard to get right now, but a 440 style aftermarket will be easier to come up with.

Well thanks for clearing that up for me lol

I've seen and heard of a lot more RB blocks, 413, 426W and 440 breaking the main webbing than the 400 blocks when you push them on the tune ups and HP On a half way serious build on either one I would (and do )replace the main caps with a good set of after market caps and studs, eaither Ductile iron or aluminum Always sonic test every block before starting any work on them How much power are you wanting to make? If above 700 HP go with a good 400 block

The one other thing that isn't mentioned enough is running a center weighted crank. When I went to one in my Megablock, the cap walk issues went away. I spin it 7500 plus rpm, and the bob weight is heavy at 2432.
Do that in a 400 block, and I wonder just how much power could be put to the block and have it live a good life. Maybe as much as you could make with B1 heads?

Greg - whats the cost difference for the centerweighted crank vs commonly available cranks?

Glad I posted that, so helpful
[crickets]

Plenty of builds with both blocks. So being that the low deck block is lighter, more compact and stronger is a no brainer. Still plenty of decent intakes out there. I'd worry about a stock block before a high dollar crank, I'm sure the crank may help but by then I'd be running a aftermarket block.
Doug

Has anyone ever considered the number of b to rb blocks actually being raced? Could potentially skew the numbers as far as failed blocks?

I paid $2305 for mine from Crower, but it is made of the best material used in any forged crank. Other companies may make them, (Ohio? Callies?) and at a lower price. If the difference is $700 to $1,000, one busted block with a non counter weighted crank and you would have been even money and a lot of saved time going with the good crank $$ wise.
Edit; Scat and Ohio are worth a call to see if they will build a crank with center weights. Scat does Billet cranks, so does Ohio. Ohio lists $1645 for a Hemi race crank for fuelers. They might build one for a standard app on request.

I'd agree an extra $1K for much longer service life is a good value over prepping another block - assuming you catch the first one in the "cracked but working" stage.