i've been breaking in my 283, got about 400 miles on it and at 45 miles an hour clack, clack, clack. i cut it off quick and rolled to the side of the road. WTF? i gave it another try to figure out where the sound was coming from, sure enough, pulled the valve cover off and the valve was sheared in half up by the keeper which i found both halves. the valve didn't have enough room to hit the cylinder walls but hacked up the piston pretty good. i pulled the head this morning. should be warrantied by the engine builder, but what would cause this? i'll drop the oil pan to make sure there isn't any bits of stuff down there and make sure the oil passages are clear, i guess i'll bring the motor guy a head and a piston to be fixed. i don't want to send the whole motor it took him a year and a half to build it the first time.
The keepers may not have been seated properly in their grooves on the valve stem, would be my best guess. ---John
Could the valve tip/rocker arm angle been off enough to put lateral force on the valve stem? Maybe the guide wasn't installed properly? Just guessing here. What kind of valve was it? Roller tip rockers or stock stamped? Posted using the Full Custom H.A.M.B. App!
Were the keepers sheared (the ridge that is supposed to ride in the groove)? If it is sheared, the valve had high seating velocity, likely from lash in the system. High lash can be caused by improper assembly, stuck hydraulic plunger on the lifter itself, or low oil level in the pan (aeration). If aeration, the other keepers will show shearing also.
I must get a different version of postings than many of you get. My version has the original poster saying that the valve stem broke. If the keepers fall off and the valve hits the piston and the piston breaks it, it will break inside the combustion chamber. This one broke near the keeper end so I would suspect the problem is the valve. Possibly the heat treating process went wrong.
Seen both. If the keepers are hardened they likely won't shear with high seating velocity but the valve will break at the sharp corner in the keeper groove root. I worked at an engine oem for many many years and saw lots of these when we had an oil consumption problem (vendor made a tiny change to the ring manufacturing process). The oil level would run low, lifters collapse, and the keepers would shear, allowing the valve to drop, usually punching a hole in the cylinder wall. Tried hardened keepers and the stem would snap at the keeper groove root, once again letting the valve drop into the cylinder. Problem could be readily duplicated on the dyno or on the road. Scattered a dozen engines verifying it. Fixing oil control (top ring actually) made the warranty problem with valve drops go away.
yes sheared at keeper groove root. the rockers are pressed steel. cheap shit was my first guess, but wanna cover my bases when i put this thing back together. agreed not much of a builder, perhaps losing a step or two with age.
Unless you have a ton of $$$ in parts and machine work in that 283,I would scrap that engine and start from scratch,yes I know its money down the drain but I sure would not trust whatever type of assembly the so called "engine builder " did for a second go around. Just my 2 cents.
I had damn near the same thing happen.... A buddy bought a bread truck, off a company to scrap after he parted it out..... We couldn't figure out why they where scrapping it..... I got the new GM crate engine. ( 1986 350 block) This was my pet peev..... The New engine wasn't runnin right, the garage gave up on it.... I did a compression check and found the bad cylinders.... I pulled the heads off, My valves where mushroomed bad but didn't break off.... Unless you buy good valves, GM supplied cheap Japanese steel valves. They are very suseptable to failure..... This engine failure was caused by a plugged EGR system, or a lean fuel mixture..... It over heated the cylinder head, warping the valve..... If they would have kept going with it, it would have snapped.... SO I did a valve job, used stock older chevy valves, and no problems since.... Low fuel psi or a lean condition will cause valve failure in any engine from excessive heat.....
I'd guess it was excessive lash. Was this a stock or perf cam? what happens with excessive lash is that the valve hits the seat while the lifter is on the high velocity portion of the cam flank rather than at the ramp. The lash could be because of a bad lifter plunger (debris) or insufficient preload. I wouldn't totally rule out bad valve machining, but there should be signs of a really sharp corner in the root of other valves, as they were all likely machined at about the same time with the same tool and the same setup from the manufacturer. If I recall, many TRW valves would have a hardened tip welded to the stem prior to finishing but it is above the keeper groove and causes no problem as long as they didn't miss the hardening process, which was known to happen. Eaton sourced valves were stem welded near the head and would corrode in the weld and drop the head into the chamber. That's not your problem though. Most aftermarket valves like Manley are probably still just relabled or made to order by one of the big valve companies. They are basically marketers, not manufacturers. I've been retired for several years so I don't know who the players are anymore after the supplier mergers/ bankruptcies/ acquisitions. Lots of valves come from Brazil now, but are good quality.
gonna pull the motor and start over, i'm having a problem trusting anything done to this thing at this point.
i'd like to know the brand of valves if you can find out. i just redid a 283 with all new valves and hope they are not the same brand
What do you have for valve springs ? Are the retainers bottoming out on the valve guide ? Coil spring binding?
The piston will be OK. The valve did not hit the edge. Keepers are not stripped. Valve broken at top groove. NOW will the shop warranty the valve or blame it one you!!!!
The picture isn't really clear but I don't see any signs if inclusions in the broken tip (small part) that would be visible if this was the result of a "cheap valve". I think the surface shows "beach marks" which are consistent with a fatigue failure, ie high seating velocity, as I previously indicated. This is an assembly issue, not a parts quality issue, unless a better picture shows an inclusion. Check the lifter for function (sticking) and look at a couple of adjacent valves. Glad the short block is ok. Actually, looking at the picture closer, it is possible that only one half of the keeper assembly was seated, putting a bending moment on the tip, and the valve subsequently snapped in the root of the groove. Same cause though: assembly error.
Doesnt really matter what we all think! You want it fixed and the problem corrected. Your first stop should be back to the builder, heres where the quality comes in. A good builder will see the problem , fix the issue and return to you like right away. Buying parts is pretty tough today with all the jap stuff out there. ( off shore) I wouldnt be so quick to hang the builder........
And being a bull in a China shop instead of doing a thoughtful and detailed failure analysis isn't going to stop a recurrance of the problem. Let's learn from failures. The option is to repeat them.
I would be concerned about the rest of the valves unless only one valve was replaced. The pictures are a bit blurry but it almost looks like the groove area was soft but the tip was hard. I've seen coil bound springs cause bent push rods, broken rocker arms or push rods pushed through rocker arms but I haven't seen a valve break off like that. We built a 289 and used Chevy valve springs that, without any coil bind, were stiff enough to split the stock Ford rockers so they slammed the valves shut real hard to try to stop valve float at 8000 rpm. We never broke a valve though. I'm still of the opinion that there was something wrong with the valve. I've always liked to use old parts because they've had thousands of miles of testing.
''Most aftermarket valves like Manley are probably still just relabled or made to order by one of the big valve companies. They are basically marketers, not manufacturers. I've been retired for several years so I don't know who the players are anymore after the supplier mergers/ bankruptcies/ acquisitions. Lots of valves come from Brazil now, but are good quality. '' Right. Very few valves are produced in the US. Yhey are marketed by american companies but made elswhere. A large factory was set up by US companies in Argentina a few years ago. A very large percentage of replacement valves come from there. Or Israel, Spain, Italy, Pakistan and of course China..<!-- / message -->
Snapped them like that many times on dyno validation tests to replicate a field problem as noted in my earlier post. Hardened 2 groove keepers, low oil level / collapsed hydraulic lifter / 3300 rpm. Extremely high seating velocity (valve closed on the flank of the cam). snapped in the groove root every time. Same test but single groove soft keepers the keepers would shear and pull the retainer through, dropping the valve or breaking the head off, but it didn't snap in the groove. We could duplicate this all day long.
although i'm not gonna "hang" the builder , i'm not bringing it back. however i did send pics and he is aware of what happened. i pulled the motor yesterday and will get it over to another shop for some investigation. i don't know enough about this stuff to effectively diagnose what happened. i want to do all the valves and address the piston top. should have it over there this week for a once over. i'll post any new or interesting info.
When we built the 302 for my Son's T bucket we were rushing to get it done and we bought the wrong length pushrods. It ran for a while but then it broke the tip off of one valve. We replaced the valve, bought the right pushrods, and the car now has a bunch of miles on it with no problems. You might be ok if you just do that one valve too. Don
Can you see a gap between one or both faces of the locks/keepers on the surviving valves? In this picture there is a gap on one side the lock pair, and the face on the other side are butting. http://www.ls1howto.com/howto/fbody/camswap/pics/325springcompressor.jpg There is supposed to be some gap unless the valve is intended to rotate, but I think that style is more often multiple grooves. http://www.corvair.com/photo-index/C124RP.jpg
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