what will break valve springs?

Old 06-26-2008, 03:30 PM
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altune
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Default what will break valve springs?

I installed aset of Manley nex tec springs on a set of high flowing 867 heads. Ran the car for two days, ( it's a drag only car )
found we had some rubbing on the springs and surrounding area of the head ,( 1.645 diamiter springs on sbc head ) so when I removed the head and took off the springs / valves I discovered one inner spring had broken pretty much in half. The cam in the thing is total lift with rocker ratio of .726 and I checked for spring bind before I initially assembled the heads. no problems there. Just wondering if I just ran into a badly manufactured spring? Anybody?
Al
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Old 06-26-2008, 07:17 PM
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topcat572
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What was the installed height?
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Old 06-26-2008, 09:34 PM
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altune
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height was 1.95 " and no coil bind I could measure.
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Old 06-26-2008, 10:00 PM
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jmarksdragster
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What RPM? How big are the pushrods? Springs that big need larger diameter PR's to cut down on flex.
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Old 06-26-2008, 10:18 PM
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altune
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car is rev limited at 8000
pushrods are the manton salt trated, thickest sidewall I could buy.
$250.00 push rods
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Old 06-27-2008, 05:28 AM
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gimmemud
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How far were they from coilbind, just because they werent coilbinding dont mean they are setup correct. Your springs should have a tolerance as how far from coilbind they should be @ full lift, mine are around 80 thousandths from coil bind and they took several shims to get there, I run the PAC springs and over .950 lift and 9000+ rpm, if they arent setup right you could be having spring surge.
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Old 06-27-2008, 06:36 AM
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jmarksdragster
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What is the Spring part# and how big is the cam?
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Old 06-27-2008, 03:42 PM
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altune
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221424- 16 manley 2.0 inch installed ht. 250 seat , 800 open coil binds at 1.070 total lift on cam is .720 so it should not be a problem. as for coil surge, not sure if that would be an issue?
I will do some more research and let you know what I come up with.
thanks
Al
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Old 06-27-2008, 07:22 PM
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jmarksdragster
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Just a rough guess here, 1.95 assembled, .700 lift minus .020 guessed valve lash, puts the springs at .180 to coil bind. Not too good. You can try PAC or PSI springs that will tighten it up a little, give you a little more seat pressure, maybe change the harmonics and help with coil surge. My SB2's came with Comp 947's, a comparable spring but not the quality they used to be when PAC was the supplier. Mine sit about the same height as yours and run right at 305 seat pressure. I had to tighten them up on the exhaustfrom how they were set up when I got them. 7 races and a dyno session and still look good. As far as surge, here is some good reading.
http://speedtalk.com/forum/viewtopic.php?t=8019
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Old 06-27-2008, 07:35 PM
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sg1586
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Did you see this on the Box???? Very important!!!
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