Broken Dual Valve Spring
05-25-2011, 10:40 PM
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Broken Dual Valve Spring I broke a #7 intake valve spring a couple of months ago and I have been preparing to change the springs. I bought a complete Lunati Gold set with valve seats, locks and seals. I am going to replace everything since I just found out that both of the springs in the dual setup are broken. I pulled the pushrod (Texas Speed 7.400) out and it's completely straight. The rocker arm looks like it was seated perfectly and the top of the valve seat looks like the rest of them. I'm think that Ill be ok just changing the springs. I'm pretty sure the spring broke because my tune unlocked about 100 horses that were stifled from a bad tune by the previous owner. The outer spring probably went first and then the inner spring went and that's when I started to misfire. Does anyone have any input? I want to make sure I have everything ready before I spend a good amount of time on my car. Thanks in advance. BTW...I have a Comp Cams #54-000-11 cam with .651 intake lift and .608 exhaust lift and 243 heads.
05-26-2011, 04:55 AM
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Think I would do a leak down on that cylinder just to be sure the valve is not bent. Issue with the bent valve would be the valve head could fatigue and drop into the cylinder with really bad consequences. Shouldn't take long to check and at least then there would be no question.
05-26-2011, 11:31 AM
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I don't know what caused the spring to break. I'm guessing insufficient spring tension for the amount of lift I have. I looked at my piston with a video scope and I am certain the valve did not kiss the piston. I made sure the pushrod was straight to make sure my lifter was good. I don't think it was a geometry problem since I drove the car for two years without issue (other than a bad tune). I'm going to change the springs, locks and seals and see how the car runs. If I have any more issues, I will compression test the cylinder. I have seen tons of spring threads so I know this problem is fairly common, especially with high lift cams. I appreciate all the feedback. I guess I have one last question before I get started. How much pressure should I put in my cylinder while I change my springs? I don't want to drop a valve, but I don't want too much pressure, either. Thanks.
