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I bought a brand new Chevy Crate motor from a Dealership in Illinois in May of 2011. The project took a great deal longer than I anticipated - it was over two years before it got installed and ran. Two years ago when the engine still had under 3,500 miles, the #5 exhaust push rod came out while the engine was coasting in second gear, going downhill at around 35mph. I heard a bang and it started running like crap. I was about a 1/2 mile from home and was able limp home. When I pulled the valve cover the #5 rocker arm was sideways. I then checked the lash on all of the lifters and found that many had more than zero lash. Nobody could ever give me a plausible explanation as to how this could happen. All Chevrolet would say was that "It was out of warranty" and they wouldn't say anything more. I posted that question here and never really got a definitive answer. The most popular response was that it hadn't been broken in correctly and that the cam had gone flat. The engine has roller lifters and there really isn't an incorrect way to break it in - it doesn't need the initial 30 minutes of running at different speeds the way an old flat tappet lifter motor does.
I ended up replacing all the roller lifters and all the pushrods and it ran ok, til earlier this year. The #6 intake started ticking and when I pulled the valve covers I found it had excessive lash. I did some research on the internet and got the usually answers - the cam was worn, the rocker studs had pulled (they screw in and the alignment marks were still lined up), the lifters were worn. I read some posts that talked about the rocker nuts only being good for one set - after that they could loosen on their own. I decided to put locking rocker nuts on and eliminate that possibility. I replaced all the rocker nuts with ARP locking rocker nuts, reset the lash and it ran the best it had ever ran. Right up til it broke again. I was Idling at a traffic light when it made a big bang and started running VERY rough. I was a couple of blocks from home and again was able to limp home. When I pulled the valve cover, the #5 exhaust rocker stud had sheared off.
This was a brand new crate motor from Chevrolet. Does anyone have any thoughts? thanks.
Don't buy the parts until you're ready to use them?
I'm guilty of the same thing. I bought an LL engine harness over a year ago. Want to take a guess where it is? Actually I don't know where it is, but it's still in its shipping box. Hopefully it works when I install, or back to the vendor to buy another one.
At this point, not sure it would be out of the question, if I was on your shoes, to cut the loss and sell the engine as is and buy another brand new one and install shortly thereafter and you'll have the warranty.
I'm guessing there is/was an issue with #6 rocker arm. It must be binding..not enough travel to open all the way. First it bent the push rod then the weak link was the stud. I guess you could look at the locking nuts to make sure they didn't interfere but it would be odd that it was #6 again...
I bought a brand new Chevy Crate motor from a Dealership in Illinois in May of 2011. The project took a great deal longer than I anticipated - it was over two years before it got installed and ran. Two years ago when the engine still had under 3,500 miles, the #5 exhaust push rod came out while the engine was coasting in second gear, going downhill at around 35mph. I heard a bang and it started running like crap. I was about a 1/2 mile from home and was able limp home. When I pulled the valve cover the #5 rocker arm was sideways. I then checked the lash on all of the lifters and found that many had more than zero lash. Nobody could ever give me a plausible explanation as to how this could happen. All Chevrolet would say was that "It was out of warranty" and they wouldn't say anything more. I posted that question here and never really got a definitive answer. The most popular response was that it hadn't been broken in correctly and that the cam had gone flat. The engine has roller lifters and there really isn't an incorrect way to break it in - it doesn't need the initial 30 minutes of running at different speeds the way an old flat tappet lifter motor does.
I ended up replacing all the roller lifters and all the pushrods and it ran ok, til earlier this year. The #6 intake started ticking and when I pulled the valve covers I found it had excessive lash. I did some research on the internet and got the usually answers - the cam was worn, the rocker studs had pulled (they screw in and the alignment marks were still lined up), the lifters were worn. I read some posts that talked about the rocker nuts only being good for one set - after that they could loosen on their own. I decided to put locking rocker nuts on and eliminate that possibility. I replaced all the rocker nuts with ARP locking rocker nuts, reset the lash and it ran the best it had ever ran. Right up til it broke again. I was Idling at a traffic light when it made a big bang and started running VERY rough. I was a couple of blocks from home and again was able to limp home. When I pulled the valve cover, the #5 exhaust rocker stud had sheared off.
This was a brand new crate motor from Chevrolet. Does anyone have any thoughts? thanks.
I know from experience that the ZZ4 non reusable rocker nuts story is true. I learned the hard way after replacing a leaking head gasket (very slight external seepage only, thankfully!). Two rockers and pushrods came loose almost immediately, made lots of noise. After replacement with new nuts the engine has been trouble free ever since.
Last edited by tuxnharley; 09-07-2016 at 12:31 PM.
Reason: clarification
Looking back over your posts I couldn't see who or when the lifters where first tried to be adjusted/ re-adjusted. But it reads like lifter problems have continued for at least 2 years. I expect your cam lobes have become damagedd if not fully wiped. Regardless of cause or blame if think an inspection of main and rod bearings needed then if no serious damage cam replaced with new lifters and rockers w/ good lock nuts of course.
If you do find bearing damage the the block needs dissasembly and the block boiled/hot tanked.
Reading your previous posts gives me the impression you still don't fully understand what "base circle" is and how to correctly set preload. On a stock hyd lifter you want 1 full turn preload unless mfr specs something different (some news hyd lifters use less - read the instructions).
After 2 years of continuous recurring problems/ failures there won't be any quick fix here.
Looking back over your posts I couldn't see who or when the lifters where first tried to be adjusted/ re-adjusted. But it reads like lifter problems have continued for at least 2 years. I expect your cam lobes have become damagedd if not fully wiped. Regardless of cause or blame if think an inspection of main and rod bearings needed then if no serious damage cam replaced with new lifters and rockers w/ good lock nuts of course.
If you do find bearing damage the the block needs dissasembly and the block boiled/hot tanked.
Reading your previous posts gives me the impression you still don't fully understand what "base circle" is and how to correctly set preload. On a stock hyd lifter you want 1 full turn preload unless mfr specs something different (some news hyd lifters use less - read the instructions).
After 2 years of continuous recurring problems/ failures there won't be any quick fix here.
wiping out a hydraulic roller cam is kinda tough unless the lifter itself mechanically fails. if so, the result would most likely be immediate and catastrophic.
Bill
It might be a good idea to inspect the cam. Even though it is a roller camshaft, cam and lifter failure is possible. These next few photos are from my stock 1998 454 Vortec engine that was in a dually I had.
It might be a good idea to inspect the cam. Even though it is a roller camshaft, cam and lifter failure is possible. These next few photos are from my stock 1998 454 Vortec engine that was in a dually I had.
Maybe I misread the OP, How does a wiped cam translate into a broken rocker arm stud?
Very simple. If the cam is worn down the preload in the lifter goes away. With enough movement the self aligning rocker arms no longer can self align themselves on the valve tip and turn sideways and wedge themselves between the rocker stud and the spring. Something has to give and break.
Very simple. If the cam is worn down the preload in the lifter goes away. With enough movement the self aligning rocker arms no longer can self align themselves on the valve tip and turn sideways and wedge themselves between the rocker stud and the spring. Something has to give and break.
Well seen one ton of similar situations [rocker arm come off the valve] but I've never seen one get wedged and break a stud. I guess I have learned something today.
I accept the possibility of my culpability AFTER the #5 Exhaust valve tossed its pushrod the first time - 2 years ago. Prior to that I had a brand new crate motor that had not been touched - other than to replace the steel valve covers with some that mimicked the old CORVETTE script style of the 60"s.
I will offer no defense if accused of not knowing what I am doing - history has shown that claim to have some validity. I read a lot of articles about setting the initial lash on a hydraulic roller lifter valve train. They disagree on the number (or fraction thereof) of turns after getting to zero lash - but they all start with zero lash. I understand zero lash to be the point where the push rod is still able to be rotated between your fingers while the lifter is on the base circle. I reviewed a number of methods. They all talked about rotating the engine and watching the rockers opening and closing. Some spoke of being about to adjust certain intake and certain exhaust valves from the same setting. Some talked of a 1/2 turn after zero lash, some 3/4 and others a full turn.
The method I settled on was to start with #1 and work my way down #3, #5 and #7. as soon as saw the #1 rocker move I would place my hand on the rocker and have my friend tick the starter. I could feel the rocker move with each tick of the starter. I could feel it go up and I could feel it go down. When I felt no movement from the tick of the starter, I assumed I was on the base circle. It was my thought that as long as there was no visible movement and I could not "feel" any movement, I was on the base circle. In looking at pictures of a cam, I could discern no distinction between any part of the base circle - as long as I hadn't started up or down the ramp. After setting all the valve on one side of the engine I went back and rotated the engine a number of times - making sure the lifters were pumped up. I then ticked the engine over for each cylinder , watching the rockers open and close - the same method I used to set them initially. When I felt they were on the base circle I jiggled the rocker arm and tried rotating the push rod.
As you can see, the pivot ball on the #5 exhaust valve has some major wear issues. I am starting to think I have an issue with a collapsing lifter. If the cam were worn to the point where there was enough lash to allow the pushrod to exit, I wouldn't think there would be enough lobe left to make the pushrod move enough to make the rocker work. After I replaced all the lifters and all the push rods the first time, all the rockers seemed to pivot fairly well. The last time I adjusted the lash I replaced the rocker nuts with APR locking rocker nuts and again the all rockers seem to have a full range of motion.
I am starting to wonder about the oil supply to the #5 lifter. Two major issues with the same rocker/lifter/pushrod seems too much to just be coincidence
Very simple. If the cam is worn down the preload in the lifter goes away. With enough movement the self aligning rocker arms no longer can self align themselves on the valve tip and turn sideways and wedge themselves between the rocker stud and the spring. Something has to give and break.
Wouldnt the same effect be possible from reused rocker nuts coming loose and allowing the rockers to move around?
I have pulled all 8 rocker on the 1,3,5,7 side of the engine and all show what looks like very bad wear patterns. I did not inspect the rocker ***** or the rocker arms when I replaced the rocker nuts with ARP locking rocker nuts less than 100 miles ago. It is possible that all this wear occurred because I improperly set the lash. That doesn't explain how the #5 pushrod came out 2 years ago. I had the oil tested after all of the pushrods and lifters were replaced and no metal was detected. From the looks of the #5 exhaust rocker ball wear, I think there would be metal in the oil now
Are those roller rockers the same ratio as the originals? You might have given yourself a case of valve spring coil bind or value to piston interference if the rockers are a higher ratio than the originals.
I don't know yet. I am still gathering information. Even if the cam is trashed, that alone doesn't solve the mystery. I still don't have a clue how a brand new zz4 engine from the factory kicked a pushrod out with less than 3,500 miles on it. I am going to take the broken parts and examples of the worn pivot ***** and rockers to some engine builders and get their interpretation of the situation. As stated, I could easily be responsible for the broken rocker stud and the abnormal wear pattern when I installed the locking rocker nuts. However, my lack of ability or knowledge played no part in the initial pushrod issue. The fact that both issues happened to the same rocker makes me think the problem is deeper than just me. The pivot ball looks like it never seated correctly and the wear patterns resulted from that improper seating. When I installed the locking rocker nuts I tightened the nuts down on the pivot ***** by hand, jiggling the rockers to insure the pivot ***** seated. I still think all of this relates to an oil pressure problem. I intend to remove the oil filter and take a sample of the oil in to be tested. As always, opinions welcomed. thanks
09-07-2016, 11:40 AM
ZZ4 crate engine issues
