77 440 vs 70 440

[Cranky]

Oh it isn't a myth, go take a look through a few late 70's blocks. They are improved in a few areas like others have mentioned.

Yup....but those improved areas on the later blocks doesn't make the older blocks junk. And someone here mentioned too about sonic testing several blocks and got various results....mostly thinner. Doesn't the article at 440 source say differently. Been awhile since reading their article.

Never had any problems with the '67 - 70 blocks. My '72 451 low deck broke the #5 main cap, but I was running 7400 RPM. Not a good plan with a stock steel crank. Keep the RPM well below 7000 & parts will live. Outside block rib seems like very good idea. My early '65 426W block cracked between the freeze plugs.

I ran with a 68 440 block hitting 7300 through the traps for over 300 passes using a using a stock steel crank....shifted at 6800.

 

[Challenger340]

We sonic test LOTS !
Never seen a "thinner" Cylinder Wall later 70's Block, if anything just as thick or thicker in the Cylinder Wall areas than '68 to early 70's 440 Blocks, albeit the later Blocks seem to be 'softer"(lower Nickel) when Honing.
Main Webs and ribbing ? Yes there are differences and they are covered in the 440 Source article quite well.

All BB Mopars are "open" Chamber headed after 1967 starting in 1968,
but that wasn't the reason for power drops into the 70's....
it was the Piston "Compression Distances" being lowered(ALL are Flat Tops) that killed the CR.
440/383 HP motors used a hotter Camshaft than the std 4 BBL Motors, and even the lowdeck 383/400 2 BBL Engines used a softer Cam than their 4 BBL std duty cousins,
hence why stuffing a 4 BBL Intake and Carb on a factory 383/400 2 BBL Engine does squat for performance.... you still have the 2 BBL Cam inside ! and also why the 330 horse 383 4 BBL can't keep up with a 335 HP Hotter Cammed 383 4 BBL. YES they WERE DIFFERENT Cams !

 

[Cranky]

We sonic test LOTS !
Never seen a "thinner" Cylinder Wall later 70's Block, if anything just as thick or thicker in the Cylinder Wall areas than '68 to early 70's 440 Blocks, albeit the later Blocks seem to be 'softer"(lower Nickel) when Honing.
Main Webs and ribbing ? Yes there are differences and they are covered in the 440 Source article quite well.

All BB Mopars are "open" Chamber headed after 1967 starting in 1968,
but that wasn't the reason for power drops into the 70's....
it was the Piston "Compression Distances" being lowered(ALL are Flat Tops) that killed the CR.
440/383 HP motors used a hotter Camshaft than the std 4 BBL Motors, and even the lowdeck 383/400 2 BBL Engines used a softer Cam than their 4 BBL std duty cousins,
hence why stuffing a 4 BBL Intake and Carb on a factory 383/400 2 BBL Engine does squat for performance.... you still have the 2 BBL Cam inside ! and also why the 330 horse 383 4 BBL can't keep up with a 335 HP Hotter Cammed 383 4 BBL. YES they WERE DIFFERENT Cams !

Had a 70 Challenger with the 330 horse 383 and it was down much more than 5 hp! It still had the dampers on the springs and the hipo exhaust mans but it was still somewhat disappointing in performance vs how the 383 Magnum Challengers ran....

 

[brad 66]

looking at 73 not sure heads yet how do 73s stack up

 

[66Satellite47]

Yup....but those improved areas on the later blocks doesn't make the older blocks junk. And someone here mentioned too about sonic testing several blocks and got various results....mostly thinner. Doesn't the article at 440 source say differently. Been awhile since reading their article.

I ran with a 68 440 block hitting 7300 through the traps for over 300 passes using a using a stock steel crank....shifted at 6800.

I ran a '68 440 block with LY rods, TRW 11.5 heavy pistons, shifting at 7,000 RPM, going through traps at about 7,000 RPM. The stock steel crank went about 600 runs. Took it apart and tapped with the hammer, sounded like a Chevy crank. Nothing was broken, so OK. Built another motor. Point is with a stock 440 crank, keep the RPM's down around 6,500. Lots of parts last longer at those RPM's.

I did terribly abuse my first low deck 452 with 7,400 RPM trap RPM. That was the motor thhat had the broken main cap, but it still was running fine. Man was I lucky.