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Old 03-04-2011, 10:29 PM
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broken valve? valve spring is sitting off center from rocker tip.

just like the title says. i can post pics tomorrow but it's pretty simple. Was driving and all the sudden put put put noise i stopped and pulled the valve cover, looks like number six exhaust valve has broken maybe? i hope not. but the spring and valve are sitting too far out, i can push them back under the rocker but it doesn't stay, makes a loud bang and goes back to where it was. I hope the didn't tear anything up. Thanks for the help guys.

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Old 03-05-2011, 01:52 AM
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You`ll have to pull the head and find out what`s happened. But by going what you discribe it`s indeed dropped a valve. I wouldn`t start it again, as it`s likely already did more damage than you`ll want to see. In many cases if a valve breaks it takes the piston and the head out with it. In extreme cases it takes the bore out with it too. Sorry I don`t have better news.
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Old 03-05-2011, 07:16 AM
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that's what it seems like to me, i can't understand any reason why the valve spring would be sitting higher and off to the side unless the bottom of the valve has dropped off. I drove it home last night because it was late and i have to work today. I'm sure it tore the hell out of the piston and the bore. I'm so happy with this machinists work.
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Old 03-05-2011, 07:24 AM
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Quote:
Originally Posted by zoomo
that's what it seems like to me, i can't understand any reason why the valve spring would be sitting higher and off to the side unless the bottom of the valve has dropped off. I drove it home last night because it was late and i have to work today. I'm sure it tore the hell out of the piston and the bore. I'm so happy with this machinists work.
Ayuh,... It's alittle early to be laying Blame, when you don't even know what broke, ain't it,..??
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Old 03-05-2011, 01:38 PM
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ha well actually before i typed that message i went outside and pulled the rocker off to verify. yup valve is broke in half. was told all valves were replaced HMMM very weary of the quality now. Although i think i might of lucked out because the valve broke at the top just below where the keepers hook in and it seems to be almost all the way at the top so maybe it didn't destroy the piston. I'm fixing to go pull her apart. Pray for me guys
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Old 03-05-2011, 03:08 PM
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alright here's what i've found. i think it's going to be ok, second opinions?
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Old 03-05-2011, 03:57 PM
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Replace it. There are likely small microscopic cracks you can`t see. If you run this piston, it`ll stay together for about a month. A friend of mine many years ago had a 305 in a truck. It developed rod knock in the number 5 cylinder. He did a rebuild and I told him you have to change the piston, because when a rod is knocking your not hearing the rod, your hearing the piston hit the head. He said "there`s not a mark on the piston so it`s alright" so I said okay, your on your own. A month later the piston came apart, twisted the rod and forced the wrist pin into the bore. He drove it home 40 miles like that. When he took the head off, the wrist pin had cut a groove about .070 into the bore so the block was history.
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Old 03-05-2011, 04:10 PM
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Quote:
Originally Posted by zoomo
alright here's what i've found. i think it's going to be ok, second opinions?
Hypereutectic pistons tend to be more brittle than forged. I don't know that I would trust that piston- except as an ashtray...
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Old 03-05-2011, 06:10 PM
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alright i guess i'm going to go ahead and replace it just to be safe and also look into getting different heads or at least new valves because i don't want this to happen again.
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Old 03-05-2011, 06:16 PM
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Quote:
Originally Posted by zoomo
alright i guess i'm going to go ahead and replace it just to be safe and also look into getting different heads or at least new valves because i don't want this to happen again.
There's nothing wrong w/waiting on some more opinions on this. My opinion is not based on actually having a problem when reusing a piston w/damage like that, so take my "advice" w/a grain of salt.
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Old 03-05-2011, 06:30 PM
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Let me resay what I meant. If you don`t want to replace it I can understand as it`s more work and perhaps the piston is okay. However why I say replace it is because of the maybe. In a month the piston could break, and then you`d be right back at square one and I know you don`t want to go through this again. Since you have it down this far you may as well go all the way to remove any doubts. Sorry, I`m not a gambling man.
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Old 03-05-2011, 08:49 PM
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no i understand guys, i'm so freaking tired of having problems. i keep dumping money into motors just to have them break i really want to do this right. I had understanding that the valves were replaced but i can't understand any reason that one would have broke if they were replaced. and as far as the pistons i don't want to have a maybe it's not that big of a deal to drop the pan and replace that piston. i can say this though, from now on i'm doing my own work. Every engine i've had built has had stupid problems like this that shouldn't have happened. Always with a machinist someone says is so reputable, i'm not blaming anyone because i don't have any facts, it could all be coincidence. I do know that i will feel a lot better if i just do it myself though.
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Old 03-05-2011, 08:55 PM
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Also just a though, i can't think of countless times that hondas have came in with a broken timing belt, and it will bend several valves. I just pull the head and replace any damaged valves and put it all back and it's always been fine. but i guess those cars aren't 400 hp either. I dunno i just don't want the what if. Also i found when trying to repair the head, it bent the valve bad when it smacked it and widened the hell out of the valve guide, like a lot, i'm not really good with measurements but i would say you could almost fit the thickness of a business card in the beside the valve stem. So what do i do with this? i've been researching, can't find a definite answer to whether or not i myself can install a new valve guide, or an answer to whether or not it's too messed up and has damaged the head. I'll take pics if necissary.
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Old 03-05-2011, 10:40 PM
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The guide will have to be drilled out and replaced. They make thick wall and thin wall guides in bronze as well as cast iron.
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Old 03-06-2011, 12:19 PM
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Quote:
Originally Posted by zoomo
I had understanding that the valves were replaced but i can't understand any reason that one would have broke if they were replaced.
That the valves were replaced means very little, as far as durability goes. If they were replaced w/the cheapest off shore valves available, I would have severe reservations that the valves would be even half as good as OEM pieces- which are not as bad as some make out, other than being 2-piece in most cases. Do you know where the valves came from, or how much the set cost?

If you can show the broken ends of the valve in a close up, well focused photo, there may be evidence of what caused the break in the first place.

Things to check would be valve stem to guide clearance- if the clearance isn't enough the valve can momentarily seize in the guide allowing the piston to hit it.

The geometry- if the geometry is far off, the valve can be pushed 'sideways' as it's opened. If bad enough, this can impart enough stress to cause a break up at the lock/seal grooves- where this valve broke, IIRC.
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