Broken valve springs

[tonka]

So I have been reading and trying to figure out why I broke 2 valve springs at `1500 miles. Life so much easier for the ignorant, but I have either learned alot or at least became aware of how much there is that I don't know. My original set up had .504" intake/.5184" exhaust valve lift with k-motion700 springs. If my installed height is 1.700 and I use the exhaust lift of .5184
that should get me to an open height of 1.1816". If I include .06" for coil bind freeway space I show 1.1216" as what would be the the max acceptable coil bind height? K-motion shows coil bind at 1.05" so I should be .0716" to the good, above and beyond .06 freeway space. If my math etc is correct so far so good. However Kmotion shows a max lift of .500" for the k-700
spring. Apparently so far is NOT so good since the travel I am generating is over .500 for both, yet should be inside of coil bind problems. So, I look at the k750 which has similar specs as far as installed height and coil bind of 1.05" BUT it has a max lift of .61" which is within any spec I can think of at the moment. Is this a possible solution or is my math and understanding of the problem still wrong? It seems to me there is an issue of not just coil bind, but the overall travel of a spring that needs to be considered, or am I just stupid :lol:

Grumpy this might look familiar to you from another forum and I have read and read on this as you suggested and the above is what I came up with. I know this discussion doesn't consider seat pressure etc but according to cam and spring manuf I should be ok.

1.7000 installed height 1.7
- .06 freeway -0.5184
- .5184 max travel exhaust -----------
--------------------- 1.1816 open height
1.1216 max coil bind heigth available

1.05 spec'd as coil bind by k-motion- (0.0716 excess room) ??

.61 shown as max lift by kmotion leads to 1.7000
-.61
----------
1.09

1.1216
-1.09
--------
.0316 within margin ??

 

[tonka]

Bleh my math examples got spread apart on posting, but hopefully it makes some sense.

 

[grumpyvette]

ok reading thru your posted info we have an installed height of 1.700 and a max lift of 0.5184 , plus the 0.060 required as minimum clearance results in 0.5784 subtracted from 1.700=1.1216, of compressed valve spring , but coil bind is at 1.0500, giving you at least in theory about .070 thousands additional clearance
your math is fine as far as it goes but coil bind is only a single factor, theres other potential areas of clearance that can cause problems, for example retainer to valve seal clearance

http://www.fordmuscleforums.com/engine- ... tools.html

If your not sure about the proper installed spring height,spring load rates,valve shims ,valve spring seat and required clearances,why not have the machine shop suggest what would match your current needs after telling them the clearance requirements and cam lift.
remember longer valves generally require longer push rods and getting the rocker geometry correct is critical to durability, shims & spring seats can easily be used to shorten installed spring heights,they also make .050 off set valve keepers and .050 off set spring retainers so you can adjust installed height over a full .200 with the same valve length.
a .100 longer valve gives you more clearance and should be fully adequate, but remember load rates have a good deal to do with both the spring and its installed height.

READ THESE

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=1005&p=15534&hilit=spring+shims#p15534

viewtopic.php?f=52&t=697

viewtopic.php?f=52&t=4962&p=13814&hilit=spring+shims#p13814

it should be obvious that the slot clearance in some rockers , especially with poly locks significantly limits rocker movement before clearances become an issue

http://www.fordmuscle.com/forums/engine ... tools.html

http://www.lunatipower.com/Tech/Valvetr ... gTech.aspx

viewtopic.php?f=52&t=2768&p=7190#p7190

viewtopic.php?f=52&t=1716&p=4250&hilit=beehive#p4250

viewtopic.php?f=52&t=282

viewtopic.php?f=52&t=1751

viewtopic.php?f=52&t=1489


viewtopic.php?f=52&t=181

http://cranecams.com/?show=valveSpringsFAQ

http://www.compcams.com/information/Pro ... veSprings/

obviously getting the clearances wrong, or over reveing the engine can cause problems

http://www.compcams.com/Technical/FAQ/ValveSprings.asp
once youve selected the new cam and new springs and thats fine but in most cases new springs require the clearances be verified and that usually requires new valve spring shims,retainers,keepers or machine work on the heads to get the correct installed valve spring height, spring load rate and clearances, failure to do so usually results in valve train problems
Its rather common for shops to install new valve springs without doing the matching clearance checks on installed height required to prevent spring bind with a high lift cam, if the engine spins without binding they figure its fine! which may NOT be the case

http://www.cpgnation.com/forum/comp-cams-how-valve-spring-tech-2047.html

http://www.lunatipower.com/Tech/Valvetrain/ValveSpringTech.aspx

http://www.enginebuildermag.com/Article/47631/the_truth_about_valve_springs.aspx

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=181&p=749#p749

http://www.chevyhiperformance.com/t...heads_valvetrain/0612ch_head_build/index.html

 

[tonka]

So the 750 allows a bigger lift (.61) than the 700 (.50) and exerts more pressure, with the same spec'd coil bind height (1.05). Somehow that seems odd but it is what they say it is. Guessing going over the spec'd travel leads to strain hardening or some such thing. I'll get out to check the seal/retainer clearance when it warms up ... flippin COLD in Denver

Thanks for those links, still learning, still fun, and really didn't think I would be discussing coil bind heights when I decided to get the vette running again after 15 yrs in the garage

I didn't know what coil bind was hah

 

[grumpyvette]

theres hundreds of ways to destroy an engine, but a common route is trying to compress solid objects in the combustion chamber,where theres not nearly enough clearance,or having the valve train bind up due to clearance issues or reveing the engine above its valve control limitations.
failure to keep the pistons from hitting the valves, bending valves, ,over reveing the valve train and having un-controlled valve movement, or having chunks of piston,that detonation can break loose, being compressed against the heads,can result in the cracked cylinders, and bent rods like the pictures below show

heres an example of wear on a binding valve train,
thats obviously not normal wear,issue and it takes a huge amount of force to pressure shear the valve tip,in that short time,

Id bet you you find its a CLEARANCE issue, that type of damage usually indicates valve train binding, if your binding the valve train,pressure are immense, and parts fail rapidly, the most common on big blocks is the rocker slot binding on the rocker stud or spring bind or retainer to valve guide issues ESPECIALLY if the cam has more than about a .530 lift and your still using stock valve springs and rockers
but check the piston to valve clearance, verify the installed spring height,(you could have to many valve seat shims) and if you adjusted the pre-load or lash on the valves COLD ID strongly suggest AFTER VERIFYING CLEARANCES that you adjust the valves AT IDLE

read thru the links

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=282

viewtopic.php?f=52&t=1005&p=1818&hilit=+shims+spring#p1818