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I’ve never seen a valve stem go up the intake. That’s a first for me personally.
Its impossible to put into words how fast everything moves around during an event like this. There will be witness marks on stuff that shouldn’t have them. Having said that, is there a mark on the bottom of the valve cover, directly above the suicidal intake valve by chance?
Definitely got off easy, I've seen the damage that it causes when they let go at 7,000+ rpm and it's not pretty.
I don't see any obvious signs of piston the valve contact prior to the valve breaking but I would double check piston to valve clearance when it gets put back together.
As far as the cause it could have be one of several, Usually it involves piston to valve contact but it can also be just plain ol fatigue. On race engines it seems to happen when you run to many rpms. Sometimes the cause is obvious like a missed shift or shifting into the wrong gear and over revving the engine.
Sure does suck but at least it's fixable and not a $60,000 engine lol
I’d be really interested to know what caused the valve to break with only 20 miles on it.
The short block had 20 miles on it, I bought the heads used, had a local machine shop clean and pressure test them, and install the valve springs on them.
I contacted the seller I bought the rocker arms from, turns out there are not stock and that they're aftermarket arms.
I've seen a thread in the past where a guy had a failure with the aftermarket ls3 intake rocker arm with low miles. I think that the rocker might have broke first, which pushed down on the retainer, which allowed the valves to drop into the cylinder
I contacted the seller I bought the rocker arms from, turns out there are not stock and that they're aftermarket arms.
I've seen a thread in the past where a guy had a failure with the aftermarket ls3 intake rocker arm with low miles. I think that the rocker might have broke first, which pushed down on the retainer, which allowed the valves to drop into the cylinder
Possible but not likely. Looks like the typical valve failure.
Possible but not likely. Looks like the typical valve failure.
Wow. Another story on broken l92 valves. I wonder how long i have until mine let go. I was going to have my heads ported by Texas speed. I guess I'll get them to install a new set of valves while they're at it
Wow. Another story on broken l92 valves. I wonder how long i have until mine let go. I was going to have my heads ported by Texas speed. I guess I'll get them to install a new set of valves while they're at it
I got a friend who had a L92 valve failure on the dyno recently. IDK what the deal is. Whatever it is, i have heard several say it is not affecting LS3 valves. no clue why one and not the other
I’ve never seen a valve stem go up the intake. That’s a first for me personally.
Its impossible to put into words how fast everything moves around during an event like this. There will be witness marks on stuff that shouldn’t have them. Having said that, is there a mark on the bottom of the valve cover, directly above the suicidal intake valve by chance?
Man I have a good one in the shop right now, swapped the motor on a 4.6 ford 3 valve last week because one of the intake valves broke and the tulip somehow got wedged up and behind the other intake valve in the freaking port. Not sure how it got up and behind the other intake valve. Giant hole in the piston. No sign of the stem from the rocker. The rocker arm is trashed too.
There is something rattling around in the intake manifold, several somethings. I'm guessing it's the stem from the valve after seeing this thread.
Man I have a good one in the shop right now, swapped the motor on a 4.6 ford 3 valve last week because one of the intake valves broke and the tulip somehow got wedged up and behind the other intake valve in the freaking port. Not sure how it got up and behind the other intake valve. Giant hole in the piston. No sign of the stem from the rocker. The rocker arm is trashed too.
Not to get too off topic from the original post, but I've got a 3 valve Ford 5.4 at the shop that had a broken rocker arm that popped the retainer off of one of one intake valve spring - the spring was just laying at the bottom of the cylinder head, and nothing was holding the valve in place but the seal - and the engine was still running. Somehow, the valve stayed in place, and that cylinder had 185 psi compression.
The whole reason why the truck came in was because the cam on the OTHER bank jumped time, and had 250+ psi on every cylinder.
Not to get too off topic from the original post, but I've got a 3 valve Ford 5.4 at the shop that had a broken rocker arm that popped the retainer off of one of one intake valve spring - the spring was just laying at the bottom of the cylinder head, and nothing was holding the valve in place but the seal - and the engine was still running. Somehow, the valve stayed in place, and that cylinder had 185 psi compression.
The whole reason why the truck came in was because the cam on the OTHER bank jumped time, and had 250+ psi on every cylinder.
Bringing this thread back from the dead. I'm in the process of rebuilding this engine. I had the block repaired at the local machine shop and the remaining cylinders re-honed to get them back in spec. The repaired cylinder has a slight gap between the block and the sleeve. Should I be worried about the gap?
01-02-2019, 08:28 PM
