The Dodge Challenger Message Board

Hello !

Someone now the difference between a 70 440 magnum and a 73 440 magnum ?
Thanks.

In just plain mechanical terms very little except for a big drop in compression and maybe cam profile. Heads may be closed chamber but 72 on will always be open chamber.
In terms of incar installation there's more to consider, loads more emissions equipment, electronic ignition, etc

Ades, right, the big difference was the pistons used. In 70 the deck height was more pronounced resulting in more compression. The 73's pistons sit in the cylinder a bit lower resulting in reduced compression. They make almost the same torque however at low RPM's. I'm pretty sure all 68-78 440's used Open chamber heads. The only 440 heads to my knowledge that were closed chambers were the 1967 '915' heads.

I seen on internet the 73 make 275 Hp, it make realy 100 hp less than the 70' or the test was not the same ? ( I hope this sentence is understandable ?) So if I change cylinder heads and piston I can have the same compression than a 70' ? My 73 have a Toker II intake, msd ignition,holley carburator,com camp camshaft,com camp lifters and stainless long tube exhaust.

Apewalski70 wrote:I seen on internet the 73 make 275 Hp, it make realy 100 hp less than the 70' or the test was not the same ? ( I hope this sentence is understandable ?) So if I change cylinder heads and piston I can have the same compression than a 70' ? My 73 have a Toker II intake, msd ignition,holley carburator,com camp camshaft,com camp lifters and stainless long tube exhaust.

Apewalski,,don't forget,,the power ratings of Chrysler Engines changed from 1971 on. What they did was measure engine power without any accessories like the water pump, alternator, power steering pump ectt this gave the impression that the 70-71 engines having much more power. The engines measured from 72 on had to have the accessories all figured into the power output which of course lowered this figure. Detroit had to comply with new federal regulations regarding advertised power numbers. There are a few options to increase the compression but the best way is too use new pistons. You can also use cylinder heads that have been surfaced to reduce the swept volume or chamber CC's,,this will increase the comp. ratio but it's a permanent modification and not the best technique. Remember Horsepower is a mathematical formula. The higher you can take the torque peak in the RPM range,,the more HP you can theoretically make. The ideal scenario for both compression, Quench or Squish is to have a piston that comes up to the block deck height at "Zero Deck" this means it's even with the top of the block at TDC,(Top Dead center),,then set the piston to head clearance at .040,(minimum) to .060 (Maximum),, with just the head gasket,,,,assuming a Flat Top piston with valve reliefs at 15 degrees. Hope this helps

Eddie, Its all I wanted so yes you help thanks you

You' re very welcome my friend!

Wasn't '73 also the year they went from forged to cast internals?

fal308 wrote:Wasn't '73 also the year they went from forged to cast internals?

The crank was the only change from forged to grey cast iron,,and yes around 73-74, they started to use the cast pieces. Some truck, motorhome, Marine,,still used forgings way past 73 though, and some pass cars too,,depended a lot on the parts surplus Chrysler had at the time. Ive seen a 1974 440 with a forged crank,,don't know what it came from at the time,,probably a MotorHome or Truck engine. The rods have always been drop forged steel, the pistons always have been cast aluminum/silicone. The rings plain soft cast iron.

Engine spec from year to year here;

http://www.nhra.net/tech_specs/engine/

Compression dropped from 9.7:1 to 8.62:1 both with a 21thou head gasket.

Cam spec also changed from .455/.470 lift and outer spring with internal damper to .443/.456 lift with outer valve spring only.

Mmm. I wonder if the NHRA inspectors got it wrong? Or??

Thanks Eddie. I meant to say cranks but was busy at work when I wrote that. Damn work interferred with my online web time I believe you're right about the forged cranks being used later in trucks and motorhomes. Motorhomes esp. have some really weird specs on their engines. A great example is the 413. It quit being used in cars around 62 or 63??? but was used in MDTs and motohomes until the '70s (72, 73 or thereabouts??) Sorry, got to get back to work now.