Broken Valve Spring

[LAA66]

 Went for a drive yesterday with the family so kept things pretty mellow in the Challenger. About 10 miles from home a cylinder dropped off. At first I thought it was a plug or something as there was not a clacking noise. Limped it home, checked the plugs, and #4 was discolored compared to the others. Long story short, another broken spring. It's not the first time either so I have decided to replace all of them.

 Can someone please recommend a spring set they have use long term, compatible with a Chrysler purple shaft cam (.484 lift 284 duration) I don't want something to heavy just enough to spin about 6500 RPM.

 Thanks

 Jon

[moparniac]

Turning that kind of rpm I would reccomend comp cams 929-16 I believe they are...

[LAA66]

 Thanks for the reply moparniac. I looked up that number in Summit. 1.535/.755 Is that the correct O.D./I.D. for a 340 with stock heads? Also these appear to have the highest spring rate and seat pressure. Would that be necessary given my criteria. My concern is pulling the valve throught the aluminum retainers.

  Do valve springs simply wear out and break? Had these in the motor for 50k+ miles, they are Sig Erson dual springs I believe.

[matt63]

You need to get the right spring for your cam.  You might be able to get away with stock 340 springs but I would check the Mopar Performance catalog or website for the matching springs for your cam.  I can help with this if you can't find it.  If you want you can cross these over to a similar Comp Cams spring but they must have the same dimensions, spring rates and open/closed seat pressure.

[LAA66]

  Thought to compare comp cams kit in a simulator lift then use the spring recommended. At summit the MP information was a bit vague for above and below .500 lift.

 What about the aluminum retainers, are they old school as chromoly and titanium seem to be the only materials listed. The retainer taper and dimensions must match the spring ID and valve locks also,,, correct?

 This is confusing!

[matt63]

Springs are selected both on lift and rate of lift.  I don't much about the retainers and keepers.  I thought the stock retainers were steel or hardened steel.  They should be fine for street/strip.

[moper]

Most springs are larger than stock diameters, and stock retainers will work, but are not exactly waht it should have. You can vastly improve the retainers and locks when you replace springs,  even when you run stock valves. MP springs have had a tendency within the past few years of having issues. Especially with higher spring rates. I dont use them any more. Comp or Cranes for my stuff. Comp is recommending double srings.. pn 995-16 for thier Nostalgia 284/484. If you have single wound springs for taht cam, that may be part of the problem. A single spring design will work with the installed height, but the tension isnt high enough for that cam's duration. The end result is fatigued springs faster than they should have been. Your heads need work to run dual springs if they dont now. The guides need cutting down, and the spring seats need machining to accept the larger springs..and you'll need retainers and locks for them. Factory stuff wont work with duals.

[LAA66]

 I sure am glad you posted when you did. Just getting ready to place an order for the Comp Cams 995-16 springs along with retainers and locks.

 The O.D of the outer spring is the same as I'm currently using. The I.D of the inner spring will clear the valve guide and seal but would have to sit on the step at the base. The heads have been worked on w/bronze guides but don't know if they are set up for dual springs.

 In my earlier post I had mistook the damper for the second spring so these are singles I'm having problems with here.

[moper]

I dont know why they'd cut the guides but not seats, but that's waht they did. Comp's 284 style cam needs duals. I can see if the MP one needs for spring. Anyone have a catalog handy?