Stock magnum max lift

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71scamp78

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Curious what's max lift for stock spring. Also what is a good cam choice for stock weight 70 dart. Will be running a 3.55 gear 255/60/15 tire . Custom stall to match cam. Will be a street car primarily but will definitely see the track. Found low mileage magnum only 33k miles and I just want to swap cam, put RPM intake and carb on it and have some fun.
 
71scamp78 said:
Curious what's max lift for stock spring. Also what is a good cam choice for stock weight 70 dart. Will be running a 3.55 gear 255/60/15 tire . Custom stall to match cam. Will be a street car primarily but will definitely see the track. Found low mileage magnum only 33k miles and I just want to swap cam, put RPM intake and carb on it and have some fun.
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The stock valve springs on every Magnum engine were not adequate for the stock cam, which was a ridiculously small cam to start with. If you're changing the cam you MUST put in a new set of springs.

I'm not a cam expert so I'll let others make recommendations, but I can tell you Hughes makes some good Magnum cams (bring your wallet). They also have some great reading material on their website about the Magnums: Hughes Engines

I bought one from Hughes because they were the only company I could find that was producing an upgraded cam for the stock Magnum EFI, but you might find other manufacturers that make a good cam for your application. Good luck!
 
autopar3000 said:
The stock valve springs on every Magnum engine were not adequate for the stock cam, which was a ridiculously small cam to start with. If you're changing the cam you MUST put in a new set of springs.

I'm not a cam expert so I'll let others make recommendations, but I can tell you Hughes makes some good Magnum cams (bring your wallet). They also have some great reading material on their website about the Magnums: Hughes Engines

I bought one from Hughes because they were the only company I could find that was producing an upgraded cam for the stock Magnum EFI, but you might find other manufacturers that make a good cam for your application. Good luck!
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Yeah I figured they were pretty weak. I like Hughes have purchased lots of parts there. Always treated me well.
 
I have researched this here quite a bit. I am currently building a 5.9 Magnum similar to yours only EQ heads. Hughes 1199 valve spring kit and regrind cam (oregon, etc). Ask cam grinder for grind recommendations. Inspect and re-use factory lifters.
 
71scamp78 said:
Curious what's max lift for stock spring. Also what is a good cam choice for stock weight 70 dart. Will be running a 3.55 gear 255/60/15 tire . Custom stall to match cam. Will be a street car primarily but will definitely see the track. Found low mileage magnum only 33k miles and I just want to swap cam, put RPM intake and carb on it and have some fun.
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.525 seems to be the number but you should always check.
 
i ran a hughes cam with their spring, 223/544,and a airgap ,loved that cam in a otherwise stock motor,really woke it up.no issues for 10 years
 
Valvesprings for the Magnum
Nice blog post with lots of relevant info. I’ve only tested one stock spring on a 5.9 of unknown mileage. The engine was pretty clean inside and if I had to guess lived a easy life and I would estimate less than 100k miles. The stock spring was 95 at 1.650 on the seat and 190 open at .485. Pretty weak stock spring and barely adequate for a 4500rpm truck engine with a very mild stock cam profile. As said above ANY cam change needs to be combined with an upgrade in the spring department.
 
TT5.9mag said:
Valvesprings for the Magnum
Nice blog post with lots of relevant info. I’ve only tested one stock spring on a 5.9 of unknown mileage. The engine was pretty clean inside and if I had to guess lived a easy life and I would estimate less than 100k miles. The stock spring was 95 at 1.650 on the seat and 190 open at .485. Pretty weak stock spring and barely adequate for a 4500rpm truck engine with a very mild stock cam profile. As said above ANY cam change needs to be combined with an upgrade in the spring department.
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Ok sounds good..springs away lol
 
From what I understand and may or may not be true. The hughes engines upgrade from the r/t cam is around .533 lift maybe closer to .540 the problem is the retainer to guide clearance but the hughes locks and retainers provide the clearance. Probably the entire spring, retainer and lock kit from hughes would work. The 380hp crate motor ran .513 lift with nothing but a spring change on stock magnum heads
 
Around .470 iirr *with stock type seals.
Positive seals will allow more, probably the .500 you see with the crate mag.

As far as I know the stock springs are 80lbs seat and near 200lbs open@.400
Weak, but you have to remember the engines intended rpm range is idle to 4000 rpm. The intake is focused on ram effect,long ram.. so again the 'sonic pulses/signal' if you will..have to go the length and back ..so the longer it takes, again..low rpm.
The 413 long rams were the same idea, and that motor was not a 6500 rpm power house. They typically petered around 5000rpm.

The seal clearance is the issue with more lift beyond .470 , then the increased rpm makes the springs an issue from there out.
 
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