ill try and make this short i have a 95 z28 lt1 with auto and the engine was a rebuilt a couple thausand miles ago and in the very begining of the build we were rotating everything around for what i dont remember anymore probally just to check things and the next thing we knew a a pushrod had pushed a hole up through the stock rocker so we then assumed the lifter was bad so we got a whole new set of lifters and installed them and then a few months later with new roller rockers they snap the valve off in the same spot the pushrod went through. so then we thought maybe it was just a bad valve cause of how it oddly snapped off the top tiny part of it. so we got that all fixed and taken care of and then it broke the valve off in the exact same spot and same way again . now were thinking the roller rockers were bad so we got rid of those and put the stock rockers all back on. drive the car put several thausand miles on it and i start to notice a clunk noise when the idle is really low with the a/c on dropping it lower around 500 rpm ish and so i took apart one day not knowing what to expect and what would you know but the back part of the rocker broke off and was laying in the head somewhere and now the car is all take apart on the passenger side and i have not a clue what is wrong with it.
any help or suggestions would be amazing . thanks sorry for the length
some side notes
1 new lt4 cam
2 heads are stock with 2.0 and 1.6 valves installed
3 new lifters
4 stock pushrods
5 stock springs
6 block is bored .030 over
7 stock intake
8 pacesetter mid tube hedders
9 h/v oil pump

hopefully someone can help me out with this also it has been happening on the number 6 piston inatke valve everytime

 

you need to make sure you don't have odd sized or wrong sized push rods - did you size them when you were building it?

 

maverick made a great suggestion. give us some more info on your build. if you have lt4 cam and 1.6 rockers you should be fine with stock legnth pushrods though.

 

Stock springs is a BAD thing. Maybe not the cause opf this problem but certainly a problem.

I think you are leaving damaged parts in after each failure and that causes another failure some time later. Best explaination I have for repeated failures in one location.

 

so you think my best bet would be to just get a new set of stock pushrods? i dont know if that really exlpains it all that well put i will be keeping that in mind but also about the springs we had them machine shop that installed the valves check all of the springs and they said that they would work fine for the size of cam we were putting in the engine. still looking for a solid answer though

 

A solid answer is you used a BAD machineshop if they told you stock springs were OK on even the stock cam.

Don't trust me look around and see how many posts there are about gaining power with stiffer valvesprings on a STOCK cam with STOCK smaller valves.

You are giving conflicting onfo on valve size too. Were the valve seats in the heads replaced? That size wont fit stock seats and leave enough material to last.

 

sounds like there is a big screw up in valvetrain geometry.
stock springs are a bad idea, especially if they are used.
a roller cam needs decent amount of seat pressure, nothing rediculous. people are not even recommending the lt4 springs with that cam. you need at a min a comp 987 springs. 135# at 1.75" i believe they are. which is more than stock, and will help control things.

i wonder what the install height of the springs is. what type of valves, and locks, and retainers were used.

aaron

 

if it was the springs that were the problem though dont you think it would happen to more than 1 valve....

 

you could have bind on one valve, and not the others.
weak springs, broken inner springs. incorrect install height.
a guide issues. many many issues. there is a lot to valvetrain geometry.

aaron

 

The valve spring pocket height DO vary. Could be a seat is making one spring setup short.