440 block horsepower limits

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A buddy just sent his 440 to be refreshed and a piston change and should be grateful he did. Builder found severe cap walk and two of the main cap bolts were stripped 1/2 way down. 4.25 stroke that made 605 and was routinely hit with 250-290 shot of N20. Several hundred passes at least.
 
A buddy just sent his 440 to be refreshed and a piston change and should be grateful he did. Builder found severe cap walk and two of the main cap bolts were stripped 1/2 way down. 4.25 stroke that made 605 and was routinely hit with 250-290 shot of N20. Several hundred passes at least.
That is exactly what I'd expect to see on a 440 block that was making that amount of power for that number of hits. The production blocks just aren't designed to handle that much power for that long. The RB was designed in the late 50's to make around 300 hp at a fairly low RPM.
 
Main cap BOLTS on a squeeze motor? At that HP level?
I have been following this thread closely as I am building a limited use street brawler.
I have one of the bigger boss main blocks and am deciding what caps to use. I have billet 3 center cap set, a 5 cap billet set, and a hemi cross bolt steel cap set, and a main girdle too. ARP studs everywhere, and I will do a half fill for better strength and ring seal. I have the Speedmaster raised runner heads that I will fully port (I have an HP machineshop and flowbench) and will run around 270 @ .050 solid roller, around 11 to 1 comp, 1.6 rockers, and have a Victor and Super Victor along with HP 950, 1050 and 1150 carbs. Headers are TTI 2 1/8" step, 4.10 gears, 8" and 9" convertors and billet internals for the 727 along with a trans brake. Other engine internals are 7.1" rods, and a billet half inch aero winged crank. Overbore will be .040 or .055" and I will bore notch the block to match the valve pockets once I unshroud them.
Also on the fence about raising the ports to Max Wedge height and or widening them some too.
The 72 Challenger it's going into has Super Stock springs, two poly buckets, and the interior is in the process of being tinned too.
Already did a bar and subframe connectors, and I have the torque box and spring hanger reinforcements to install.
I am hoping for 9 anything on the motor and whatever it will run on a 250 plate.
I intend to tune it and get kicked out on the motor, then go to the other track, get kicked out on the plate, and just drive it on the street.
Main question is what caps to use? Are the hemi billet caps worth the trouble for what I am doing? Or will it kill the block anyway?
Anyone done a similar combo?
I know it's an E body, but there isn't many go fast folks on that board!
I have 275-50 R code drag radials and frontrunners too. I really don't know what the weight or performance will be. Any thoughts on the build or expected performance?
THANKS! TIMINATOR
@Jeremiah(jd)
 
Word is 440 Source will be offering a new siamese 440 iron block late 2025 early 26
Check out joe mopars youtube channel for the details he got from Brandon.
 
650 is a fairly safe number, The longer the stroke and the heaver the BOB weight the harder it is on the Mains.
 

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