The 400 block is considerably stronger vs a 440 block in the main web. I am a 400 block fan. IF, and that is a big IF, you can find a good one. Check for core shift and sonic check is a must. I had 4 blocks and only one I used for this build.

At 2860 lbs I have ran 5.44 in the 1/8. I have not scaled my car in years but I might be close to 2900 now. What is that, 8.60's in the 1/4? That is up in the 800's pretty good. Block filled. Steel caps and no girdle. I did have to sleeve #8 due to a crack 3 years ago but this block has been run every summer hundreds of passes since 2019....

In general, cylinder pressure drops with rpm so the same boost at 6500 is harder on the bottom end than at 8500 rpm. From what I’ve seen of the LS guys the boost targets are pretty flat, so if it drops a couple thousand rpm on a shift you get increased cylinder pressure and the stress of the rod being slowed down too. For oem stuff we have to be very aware of timing and boost at the various engine speeds to keep the engine safe, and it isn’t realistic to map a drag engine like that- they can’t be held at full load that long.

I thought force/stress on the block itself is primarily a function of weight and rpm though.

I went aftermarket block with mine just because I don’t like to gamble and I hate worrying, lol

Well bearings are here, boosted cam is ordered, and its like 15* in my garage, so gonna hide in the house for a day or two, but it looks like we are going to find out if a 400 will be ok making really good HP with a little boost.

Anyone know the weights of the various blocks? I had heard the after market Callies Hemi blocks I have are over 300lbs...What is a 400 block weight?

A Callies block is around 295 lbs and a 400 is bit over 215 lbs

Isn’t your duster for sale?