Rocket Racing block=254lbs
425 block filled w/Mondello steel girdle=236lbs

I also have a 425 block here with a Jeff Smith girdle which I'm confident is heavier than the Mondello girdled one. It's an assembled short block so I can't weigh it accurately. I did weigh it complete when I pulled it and will weigh the complete RR blocked engine that's replacing it using the same top end and accessories before it goes back in.

 

What do you think this is, ROP circa 2010???

 

I had this saved in my notes from a post from one of the Olds sites when the RR block first came out: "the RR block is almost 50 lbs heavier then a standard non-filled, non girdled BBO block". Based on that I assume a standard BBO block is around 200 lbs or in the low 200s. Seems to make sense with your filled/girdled weights or at least be in the ball park. Also I see RR still shows the weight of the block right on their site:

ROCKET RACING & PERFORMANCE BBO BLOCK

DECK HEIGHT: 10.625

BORE: STOCK BBO UP TO 4.400”

MAIN BEARING SIZE: STANDARD BBO

MAIN CAPS: ALL 5 4 BOLTS BILLET STEEL

WEIGHT: APPROX 250 LBS (DEPENDING ON BORE)

LARGEST BORE: 4.400”

BELLHOUSING: ACCEPTS OLDS, CHEVY, BUICK, PONTIAC, AND CADILLAC

CAMSHAFT DIAMETER: STANDARD BBO

CAMSHAFT POSITION: STANDARD BBO

CYL WALL THICKNESS: MIN .200 @ 4.400” BORE

DECK THICKNESS: ADEQUATE FOR ALL APPLICATIONS

TORQUE SPECS: MAIN 110FT/LBS
-Joe

 

One add to this - just found this that I had saved too: I have personally weighed a bare 455 Olds block using the finest Chinesium bathroom scale that WalMart sells, and it came in right at 200 lbs.