(08-27-2017 )Pdxt Wrote: [ -> ]Hey guys, looking to see if any other guys have issues with the exhaust valves "bridges" breaking? I've had two break on me in a month, fixed beside the road my self, this last time I almost lost the valve as the keepers couldn't take it. Half was already out, this was fun to fix beside the road?
Any ideas or help?
More guys having this issue?
I'm not sure why I'm bothering to dignify another response to a thread started by a brand new member that has one post asking questions about a serious issue that doesn't return and thank any information shared, guess despite my being an asshole, I'm a nice guy...
And yes I have some ideas and they may not be pleasant to hear, but the conclusions reached are logical. Argue them if you like, but I'd advise you best bring evidence cause I'm gonna lay mine out here for all to see.
I haven't heard of anyone else breaking cross heads, and by the lack of response I'm pretty sure neither has anyone else.
I'm not going to comment on the valve spring retainer keepers, the detail of the pic is not sufficient for me to see on my mobile device.
Here's what I see in the picture you posted, and here is a cropped and doodled on version for everyone to follow along at home or on road with...
[
attachment=3050]
We're going to start with the
Blue and
Red arrows first...sorry, this is just me having fun.
Please look carefully at the space between the valve spring keeper and the crossheads of these arrows. Note that there is NO valve stem visible on the 3
Blue intake valve/crosshead gap, and there is plain shi#t as day valve stem visible on the 2
Red exhaust valve/crosshead gap.
Now let's turn our attention to the rocker arm clearance adjusters. These will be the
Yellow and
Orange arrows.
The
Yellow arrows are the intake adjuster screws, and they
appear to be adjusted correctly. No way to ever know from a picture, but they appear consistent heights with my experience.
The
Orange arrows though paint a beginning to become clearer picture...they are
way the F out of atypical ISX exhaust adjuster screw positioning.
In case you haven't caught it yet, here is my summary;
If you did your own overhead adjustment, you need to learn to follow instructions much more clearly!
If you hired someone to do it for you,
FIRE THEM!!!
Hope I haven't left room for misinterpretation.
I firmly believe that whomever adjusted the overhead in this photo used the 7mm/0.276" Jake brake feeler gauge in place of the OEM spec 0.027" for the exhaust valves! Look at the picture again, pay very close attention to the
Red arrows. Does that section of exposed valve stem not look to be approximately the 7mm/0.0276" height of the Jake brake feeler gauge to you? I have never seen valve stem exposed when crossheads are installed on any of the ISX's I've worked on. (maybe a little if you get eye level to them)
Please now note the
Green arrows.
This is the point of measurement with a 0.027" feeler gauge to properly adjust the exhaust valve rocker arm clearance!
DO NOT EVER use the 7mm/0.276" feeler in this location!
This brings us to our last color, the
Pink arrow.
THIS is where you place the 7mm/0.276" Jake brake feeler gauge! Between the JAKE BRAKE ROCKER ARM and the EXHAUST BRAKE VALVE PIN!!!
Ok, 0.027" and 0.276" doesn't look like a lot, but it is
10 TIMES the measurement! 10 times anything in an engine is an astronomical change!
So let's go through what happened/is still happening in that poor motor...
Oil has surface tension, which is what makes it sticky. The oil gets between the crosshead and the rocker nose (the swivel thingy on the bottom of the adjuster screw) as it's supposed to. Rocker noses and crossheads wear against each other, that means their surfaces become a mirror image of each other, add oil with its surface tension to perfectly matching components and they soon stick together. Normally not a big deal, but because you have a ridiculous amount of clearance, the crosshead actually lifts above the valve stem surface..uh oh. Wouldn't be a big deal if oil was only sticky...but it's also slippery! Yup, as that crosshead is lifted above the valve stem, with all the movement and vibrations occasionally that crosshead works its way off to the side of the stem and it comes down half on, half off. This is why the valve stem is smashed instead of smooth as a babies bottom.
Now the shi#t.
So now the crosshead is no longer held in place by the recessed pocket and valve stem and is smashing the crap out of your stem. That's not your issue. The issue is that now because the crosshead and valve stem are out of alignment your clearance went from insanely loose, to way too tight! The gap went away because the stem is not in the recessed pocket! Now the cam lobe is coming around and pushing up on the rocker arm...the rocker arm begins pushing the valve down/open and now you have COIL BIND. Coil huh? Coil bind is when a spiral spring gets fully compressed and has no more ability to compact, it is steel to steel to steel contact and is now solid. But the rocker arm is still being lifted by the cam & pushing down on the coil bound solid spring.
BOOM Your crosshead just broke, it was the weakest link. The spring couldn't compress any more, and the valve keeper damn near failed as the cam kept pushing the valve because the clearance wasn't there. You are aweful lucky you didn't punch that valve out of the keeper, it would have been a catastrophic failure.
Now you're going to hate me.
You're not that lucky. Your cam took a shi#t kicking. The spring coil bound, and the cam lobe kept coming. You may not see it, but metallurgically it is damaged.
The cam drove the shi#t out of the rocker arm, it's most likely damaged as well. The rocker shaft saw inordinate amounts of strain as the rocker arm was being pushed up on one end by the cam, and stopped solid on the other by coil bind, so the shaft was being lifted vertically, probably bent.
That valve and valve spring is fucked, there's no way you partially push a valve stem out of the wedge keepers without damaging the valve, not that I've ever seen. (Former drag racer, I've seen it more times than I can count) When springs coil bind they are almost never completely flat, so the valve(s) are probably bent.
Its quite likely that the valve guide was contacted by the keeper or spring keeper and may have been moved/damaged. The valve guide seal definatley got destroyed.
Your head is probably toast. Either way your gonna have to pull it to change those valves. If you don't, you WILL drop one. It's not if, it's when.
Don't be surprised if a piston kissed the valve either, because the lift and duration were way out of time due to the crosshead jumping the pocket.
PLEASE NOTE!!! This IS NOT a tutorial on how to do an overhead adjustment on an ISX engine. DO NOT expect to hold me accountable for telling you something when the mistake here is so obvious, that some jackass like me from the interweb can see it in a photo! If you ever see significant valve stem between your valve spring keeper and the crossheads, there is SOMETHING WRONG and you need to correct it immediately! Whomever did this adjustment DOES NOT KNOW WHAT THE f$%k THEY ARE DOING!!!
Good god, with the exhaust valve duration being severely altered in this state, I cannot even begin to imagine the extent of the damage caused by excessive cylinder pressures, combustion heat retention and absorption, and reflected heat. I'd be absolutely shocked if the head isn't screwed. I'd be amazed if there isn't injector damage.
Whomever did this to your motor, severely abused it and quite frankly F'ed you so hard it's not funny. I feel for you. If you did this yourself, I feel even worse for you, but you need to learn how to understand directions very clearly before you attempt any repairs yourself again.