Stock valve springs with this cam?

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1975dartswinger

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I have a 318 in my 75 Dart that I put a Comp HE268 into. Head wise its bone stock. I just want to know if my valve springs will take it. I know I will be losing some RPM, I just dont want them to bind or anything. The motor is awaiting cam bearings which I am putting in shortly and I dont have a dial indicator to check this.
 
just let me tell you this afreind of mine had that cam which is amild cam in his 360 stocksprings no problems for a couple months,it broke a spring vavle droped locked the motor up ruint the block untill that happen i've runed a 484 lunati cam with stocksrings now i run matching springs, just my twocents worth
 
Well there are certainly two schools of though here. The first and most conservative is to run EXACTLY the spring the cam grinder specifies, at exactly their pressures. If you expect some sort of waranty do this. On the street, do this.

The other school is to run absolutely no more spring than you have to to prevent valve float through the traps. If you are spending the bucks for lightweight retainers, rockers, lifters, and thin stem valves then by all means experiment with this, it WILL make you faster.

Now, if you think you can install a cam with substantially higher lift, rev it higher and not break those 100,000 mile old springs, good luck.
 
I believe springs take a set and changing the working of the spring,more lift , cant be good on the springs harmonics.JMO You can change the springs with the heads installed without tearing it down using air in the cylinders. New springs is money well spent due to a failure being potentially catastrophic.
 
Stock springs cannot handle the XE268. It's not power alone, it's coil bind and lobe life. Run what Comp says to.
 
That's what I thought. Also I can get a set of magnum heads cheap from a friend. I believe they have stock valve springs and they have been rebuilt. Will those work with that cam? And what does it take to convert to Magnum heads? I know I need pushrods, and aftermarket lifters (which I have), but what else?
 
Yes you will need new springs with the magnum heads too, even more so with the additional lift from the magnum 1.6 ratio rockers. You are some what limited in spring choices for the magnum head too. Mopar Performance has two and comp has a new drop in behive spring for the magnum head now too. Also, there was a thread on another board where some one had used 3.8l GM v6 springs. In all cases you will need new retainers to because none of the springs are compatible with the stock magnum beehive size retainer.

You either need to have the heads drilled to accept an LA intake or get a magnum specific intake. And of course you need the magnum rocker gear.
 
Ok, that sounds fine. I was gonna use a Summit Stage 3 intake (Summit brand performer rpm). Does anybody know if that will clear in a late A body?
 
That intake is the Professional Products CrossWind. I have one on the 360 in my 68 Barracuda. It clears the hood with a 2" tall air cleaner with no issues.
 
Do not use stock springs! Especialy on an Extreme energy cam. It would be suicide for the engine. The agressive lobe ramps of these cams will potentially make the valve train pathetically noisy.Always replace and check seated pressures regardless if you have stock or modified heads.
Regards.
Billy D...
 
I know I need new springs. But this not an Extreme Energy cam, it is a High Energy cam. .454" lift and 268 degrees advertised duration is not a big cam but I'm guessing big enough to warrant new springs.
 
dgc333 said:
That intake is the Professional Products CrossWind. I have one on the 360 in my 68 Barracuda. It clears the hood with a 2" tall air cleaner with no issues.
Click to expand...

I was going to suggest one of those also...408 Dartman and I compared one of those to an Edelbrock side by side. The casting were cleaner, and matched better than the Edelbrock. A real nice piece for the money, and can't beat the fact they will go on either a Magnum or an LA.
 
1975dartswinger said:
I know I need new springs. But this not an Extreme Energy cam, it is a High Energy cam. .454" lift and 268 degrees advertised duration is not a big cam but I'm guessing big enough to warrant new springs.
Click to expand...

You are correct. I ran that cam for 3 years a whiel ago... passed emmisions for 2 years and still ran 13.40s NA in an E body stick car w/3.23s. It has a nice note to it too.
 
I always thought it was as quick and easy as install the cam check for clearance measure with a feeler gauge in between springs must have at least .001
 
Matt, between coils it should be .100".(i'm assuming a typo...lol) But, on a hydraulic cam, the lifter compresses during "0" oil pressure. SO you cant mearsure that effectively.
 
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