What makes a engine a magnum?

[JR_Charger]

Now that would be disappointing!

 

[dspur]

Now that would be disappointing!

Never mind! Just looked it up. Torque is the exact same at 425. See pic from old Motor repair manual I have.

 

[JR_Charger]

Put me in the "those numbers aren't real" camp.

Surely someone has dynoed a 383 Magnum and gotten the real numbers though?

 

[Ray70Chrg]

What makes a 1971 383 magnum different from any other 383

I think the biggest performance gain between magnum and non-magnum 383 occurred in the addition of the 10 3/4 torque converter in the a727. Only the hp 383 got this converter.

 

[MoparLeo]

Looks like torque is the same but at a different RPM.

 

[dspur]

I think the biggest performance gain between magnum and non-magnum 383 occurred in the addition of the 10 3/4 torque converter in the a727. Only the hp 383 got this converter.

View attachment 1529303

Mine is the 330 hp version; 69 Bee, factory Air, but with 4 speed and not the 727. I presume had something to do with having factory air etc. (If I did know I have forgotten). It is painted the aqua color and not orange, which I thought was a mistake but evidently came from the factory that way on the 330 hp version.

 

[eldubb440]

I was taught that the term “Magnum” is unique to Dodge high performance engines. Plymouth calls it a “Commando”.

are you implying all Plymouth guys go commando?


maybe it's just the pie tin

 

[Curiousyellow71]

When the hp engines came from the factory it has been said they were put together with more clearance by choice of parts selected on the assembly line. Being a tiny bit "looser" helped with longevity on the wot abuse of a performance car... vs grandma's Newport.
Of course when everything is remachined on a rebuild..none of that matters. Hp is then just a stamp on the block and their is no way to tell the difference on the heads other then looking at valve springs (if they are original).
I don't believe they had a high compression 383 by 71. I have taken apart a late 71 383hp and it even had a cast crank. It could've been swapped in possibly, but no sign of it. I was expecting forged. It did have a windage tray and double roller timing chain. Also 71 came w 346 heads, not 906s.

 

[dadsbee]

Nobody was hand selecting parts for thousands of HP engines

 

[Curiousyellow71]

Nobody was hand selecting parts for thousands of HP engines

That is correct...Not exactly hand picked. There are often Letters stamped on parts. Install piston stamped "A" in cylinder stamped "C". It was the best they could do with the quality they had. Everything was off a bit but measurable and it was easy to select looser fitting parts by selection or one that fit the best. I wouldnt exactly call it hand fitted. It was quick and simple. I had seen it, especially on some gm engines. Challenger340 got into what mopar did on a thread. Reality is they did the best they could and sent it out the door. Read post 96
440 Rebuild

 

[PlymCrazy]

are you implying all Plymouth guys go commando?

That’s about as “naturally aspirated” as you can get lol

 

[eldubb440]

That’s about as “naturally aspirated” as you can get lol

lmao...... I told the wife "I have a snorkel in my pants"


her >>>>>

 

[RemCharger]

What makes a 1971 383 magnum different from any other 383

To the original question; they dropped the compression ratio and ran 346 heads.