has anyone ever experianced this problem? i got a large cam and springs to match.after market keepers and locks.same stock valves but new,the engine is tuff as hell, totaly rebuilt 355tpi.it runs great until it pops the top off a valve (on the lower of the two grooves on the stem)were the seal goes below the locks.its happened 6 times on random valves.ive been told that the stock valves cant handle the spring rate.and they are snaping off because the presure of the spring when the valve close's is to much because the lift is so much .512/.520 i had the guides machined down so the keepers wont smash the seals.its breaking when the valve closes. do they make after market valves without that lower groove for the seal ? any input would be apreciated.thanx

 

Virtually ALL aftermarket valves lack that groove, because that seal is so worthless.

For a cam as mild as you describe, you don't need anything really spendy; just something hard enough that you can't scratch it with your thumbnail like the stock crap. I'd suggest the Manley "Street Flo" valves... they're about the cheeeeeeeeeeeepest "good" valves out there, at around $90 a set. http://www.summitracing.com/parts/MAN-10722-8/ and http://www.summitracing.com/parts/MAN-10765-8/

 

if your busting valves or any valve train component,you have a valve train clearance or geometry issue your ignoring
its just that simple, yes I'm sure you think everything's great, but if you take the effort to carefully verify ALL VALVE TRAIN clearances and geometry , youll locate the reason why your having durability issues, take the time to find,isolate and fix it, its NOT LIKELY TO BE a valve spring load rate issue, theres no evil sorcerers curse its just a fact that if parts break theres a CAUSE and in most cases its the wrong clearance or a geometry issue or lack off lubrication



read thru this link and sub links

http://forum.grumpysperformance.com/...php?f=52&t=181

http://forum.grumpysperformance.com/...php?f=52&t=399

http://forum.grumpysperformance.com/...php?f=52&t=401

http://forum.grumpysperformance.com/...ushrods#p18267

 

I don't know - just surmising - but would a spring or retainer bind cause the valve tip to break? In these conditions the valve stem would be free floating or in compression, wheres I would assume a tension condition would be needed to pop the valve tip off below the locks. Like say in float when the valve suddenly slams closed.

Doesn't this also mean a bunch of valves have disappeared into the cylinders, with resulting carnage?