Valvesprings for the Magnum

Valve springs concerning a Magnum are very limited. Currently the best drop in available is the Mopar Performance p4976062 spring and p4452032 retainer (2.2 Chrysler retainer lol). Magnums are limited due to the shorter 4.91" length valve. That ends up with installed heights around 1.650" to 1.640". Subtract 0.600 lift from that and you are already at 1.040" The valve stem seal and seat to retainer clearance is usually 0.465 to 0.470 max. So cutting down the seat and stem guide boss are required on Magnum heads. By far the most used spring combo is the Mopar Performance spring that was specifically designed for the smaller 1.420" valve spring seat machined into the heads. If you are not looking to open the heads up to 1.500" and cut the seat and guides down, then this drop in is a true bolt on for your aftermarket cams. You can simply order those from Summit or Jegs at the lowest price they both offer. Now I am designing new roller cam profiles that will work with your stock springs. Stock springs when not worn out, are lighter in mass than the heavy springs offered by Mopar. Do not get me wrong, I am not saying they are better. I am saying, if your cam profile is small enough to work with that spring, then there is no need to shift past 5000 rpm. Number one as you can see, it is only 220lbs at 0.485" lift. Number two, your long runner intake manifold is done at 4800 rpm.  Now if you are running a Mopar single plane intake manifold, then you need spring pressures that are over 300 to pull 5500+. The kits from Hughes, Performance Injection Equipment and Mopar will get you those pressures. If you think for a moment that you can rev 6500 with any of those springs and make power, forget it. Those springs will not make any power past 6000 rpm, especially with the steel retainer being 27 grams. Lighten to a titanium retainer and you will gain 100-200 rpm. The only way to make true power past that is to machine the heads for double springs or a beehive spring. The later being the best choice. A standard steel beehive retainer is 10 grams, a Titanium version is 6 grams. Plus the harmonics of a Beehive ovate spring outperform any standard in minimizing oscillation. Another option is to run 0.100" longer valves, but you will need to change pushrod lengths. Rocker geometry will still be safe if you stay below that 0.100 length. If you stay with your stock springs due to wanting low end torque for your Moab or Bear Trail machine, then for a safe setup when choosing a camshaft, keep the lift around 0.450". That gives you 0.060" or more safe bind clearance as the stock spring will bind at 0.520". That is why 1.7 roller rockers work well on stock cams and springs.

• Stock coil bind 1.125" @ 0 .525"
• 1.650" @ 85lbs stock
• 0.480"/1.170"  @ 218lbs

So as you can see a 0.480 lift cam list only gives you 0.045" safe clearance from bind on the stock spring. Better to stay safe, use a cam with a mild ramp lobe profile so the stock springs follow it closely and keep the lift around 0.450". Here is the Mopar spring info:

• 1.425" od 1.055" id
• 26 grams Mopar retainer
• 1.640" Installed Height @136lbs
• 1.150"  (0.500" valve lift) @329lbs
• .990 bind

I literally sold thousands upon thousands of this spring and retainer, yet only recorded three broken in 10 years. Interestingly enough, I have never seen or broken a stock spring in that same time. Stock springs may not be the route you are after, or maybe they are? Stock Magnum head flow is no slouch when compared to standard LA heads. Superflow test show that at 0.450" these heads consistently put out 213-215cfm with the exhaust sitting close to 73% of that flow. Mild porting will net 260 to 280s. Do not fall prey to Dodge advertising that the 360 only makes 250hp/345tq. When you run a stock cam that is 200/200 114lsa with low 400 lifts, and timing curves that barely give 20 degrees of spark advance cold, that is all you will see.  Compare that to the standard 360 build everyone ran in the past at 9.5 to 1, ported 260 cfm heads, headers, single plane intake and the old Mopar Purpleshaft P4120231 ( 0.484 241/241 108lsa cam) That combo hits 450-460 at 6000 rpm everytime and 480lb tq @ 4200 rpm. That is all bolt on parts. Change that camshaft to a 252/262 108 lsa and bump the compression to 10 to 1 and you will hit 500hp/500tq (6000rpm and 4500rpm). But you will need a better spring than the 062 to follow that cam rpm profile. So stay tuned, watch for my dyno tests upcoming using the stock springs and new cam profile that will truly be a bolt on...