what will break valve springs?

[altune]

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

[topcat572]

What was the installed height?

[altune]

height was 1.95 " and no coil bind I could measure.

[jmarksdragster]

What RPM? How big are the pushrods? Springs that big need larger diameter PR's to cut down on flex.

[altune]

car is rev limited at 8000
pushrods are the manton salt trated, thickest sidewall I could buy.
$250.00 push rods

[gimmemud]

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.

[jmarksdragster]

What is the Spring part# and how big is the cam?

[altune]

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

[jmarksdragster]

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

[sg1586]

Did you see this on the Box???? Very important!!!http://i126.photobucket.com/albums/p93/sgmotor/2008_0209Image0021.jpg

[altune]

.026 on valve lash.
So you think the springs are too loose?
the coil bind should be .060-.080?
kinda new to this part.
thanks
Al

[topcat572]

Yes, and make sure its warmed up to 160-180 degrees before You rev it. :wink:

[jmarksdragster]

Running the springs you have that tight may not be feasible, in addition to the fact you broke one they already may be hurt. I would look at the PAC or PSI, they coil bind a little higher. You can get away with as much as .120 to coil bind, but the idea is to use a valve lift that matches the spring when you start running more than about 7500 RPM. That way the seat height and open height are optimum for spring, putting coil bind height where it need to be without excessive seat pressure. Mine ended up with .075 intake and .095 exhaust distance to coil bind.

[altune]

Ok,
I have now been ingulfed by this coil bind, / spring height setup.
when the springs are installed at the height that is advertised say 2.0 inches and coil bind is at say 1.15 and my cam total lift is say .700
I should set up with .070 shim to get somewhere in the .080 range before coil bind ??
Now on the other hand, if my cam total lift was , .770 then would I be in the ball park? And if so how would that "Tighten the springs as you say?
kinda curious?
It is very interesting what happens at high speeds in the v. train.
Thanks
Alan

[topcat572]

I just went thru this with the same springs. I used a shim, standard height retainers than the normal +.100 that are usually used, and a .060 spring cup on the ex instead of the .030 that came standard. This got me in the ball park with my .800 + cam. As with most cams Ive seen, You will need more shim on the EX as it has even less lift. As I was advised, stacking a lot of shims is not good. You can also get -.050 keepers. I had 2 pages of responses when I did It, I will try to find it, Good Luck. :wink: Found it, search Speedtalk, Broke Valve Springs, by travlinman572, check it out.

[jmarksdragster]

When a spring is run closer to coil bind, it dampens the bouncing/surging when it is around peak lift because there is little room to move. If too much distance is available at peak, it can't dampen the surge. On an engine under 7500 RPM this is not as much an issue. It is even possible to have the spring set up correctly, but the harmonics of the spring is wrong for the RPM you are running. This is why I suggested a different brand. Edvanced engines Ed Wilson here is a dealer for PAC and can probably get you a fair price on them. Spend the money for an on the head spring tester to keep tabs on your springs, LSM or Pro Comp will do the job.

[Tod74]

these type of threads always seem to be centered around that same part number manley nextek spring....