Big Block Powa!! ??

“What I’ve heard” thru folklore is that a 375hp 440 would make about 315hp tested on a more modern dyno....... so the 320 he got seemed to agree with that.
Especially if you had the crank turning the water pump instead of it being electric.

(FWIW, My experience with the shims in the oil pump spring is that it absolutely works....... just like the HP spring MP sold also works(more pressure), as does the Milodon adjustable regulator)

The 426w was sort of a cobbled together mess...... but still...... under 300 is kinda weak........ but seemed plausible considering the power of the 440-4.

“What I’d like” to see them do is....... take a build like the 440-4...... after the rebuild...... where they had it in the 400hp range....... and then see what it takes to step it up another 100hp.
More cam, headers, intake, carb, etc.

It’s a business....... so it’s not like that would likely be a paying job for him...... just like I’ve never had the opportunity to do it here.
If I’m looking to end up at 500hp..... you build it to make 500hp..... and iiwii.

But going through the transformation would be fun.

From what I can think of, looking at 30 years worth of memories is...... the weakest BBM I’ve tested was a 400, that I got as a rusted seized motor, that I had to beat the crap out of to get it apart.
I cleaned it all up, hammer & chiseled the rings out of the pistons, and put it back together with new rings and bearings.
A set of very very used up 346 heads that I did yet another valve job on, along with a quick bowl blend. A used Crower 280H cam, swap meet DP4B, and a Holley 780vs carb I bought for $4....... I also went through an old 383 single point distributor.
With 1-3/4 headers on it, it made 400tq/350hp.

All the others I can think of made over 400hp, although they were all run with headers.

The “after” numbers on the rebuilt 440-4 are pretty respectable imo, especially using the stock intake/carb/exhaust manifolds.