Valve Issues

[grizzlyjosh]

Hey Folks, I've been having a knocking noise coming out of my exhaust that I have traced to a bad valve guide on the #5 cylinder. The thing is, about 10,000 miles ago, I was having similar issues and had the heads checked out at a machine shop. The guy cleaned up the couple of valve seats that needed it and checked everything else and said they were good to go. I'm not sure which valves he worked on but the truck ran beautifully for a while until this knocking started. So, whats more likely, the machine shop let me down, or something else caused this valve guide to go bad. I guess I'm trying to decide whether to pull the other head out as well and have them both looked at by a different shop. Or if I should dig deeper into the guide failure and troubleshoot that. Or both.
Also, the valve guide got bad enough that it wasn't closing far enough and made contact with the top of the piston. What kind of damage could this have caused/what do I need to check on?

 

[IDIBRONCO]

First off, be aware that 7.3 did have valve guide issues on the exhaust side. The best fix is to have bronze liners installed. I'm not going into the quality of the work/knowledge of the shop that did your work. One thing that I did notice was that you had a valve contact a piston just a few thousand miles after having head work done. These are close tolerance engines. There is a spec for maximum and minimum head thickness, valve recession, and (of course) valve clearance. If there was too much material milled off of the heads, then you may have had valve clearance issues all along after reinstalling your heads. I believe that it was MacRobb who said that he had a set of valve guides wear out in 5000 miles due to valve/piston contact. My advice is to pull both heads and look at the tops of your pistons to see if there is any contact other than the one valve that you know is bad. What can the damage be? Bent valves, cracked pistons, and even bent rods of the contact is bad enough (although I think that is unlikely unless you have a bent valve like you said that you do). Sorry for the bad news.

 

[Big Bart]

Some thoughts-

Yes pull both heads and have them gone through. Otherwise you could be back to pulling the other side in 5k miles.

If you are suspecting the machine shop did poor work ask around and see if some folks recommend a different one.

Also a valve guide would not generally collide with a piston. Are you suggesting the valve hit the piston? Could be because the seat gave out or the valve got stuck in the guide. Either way then hit the piston. Let us know what and how you think it hit.

If the valve just lightly collided with the piston it may be fine. It it smashed it a dozen times you may need to replace the piston and connecting rod. Send pics and several of the members will give you feedback.

If you have straight edge see how close to the top of block that damaged piston goes vs some others. You should be able to find out if the connecting rod is bent.

Send pics

 

[RSchanz]

Can I ask a side note? Did you pull the heads engine in or pull the whole engine? Need to replace my head gaskets and I'm trying to find more information either way and I cant really find any good videos. Maybe easier to start a PM with this...

 

[Big Bart]

I will let others weigh in, have yet to pull my heads.

But if I had a leaky head gasket. I have the tools and I have a friend with a shop who has a cherry picker, a extra engine stand, and room at his shop for me to do something like this. Since I have the tools and space I would pull the engine in case I see something I did not like. (Scored cylinder walls, semi-melted piston, etc.) Part of that decission would be so I can do some other work below while it was out.

1) Rear main seal.
2) Oil cooler o-rings.
3) Oil pan seal.
4) Heater block element.
5) Exhaust manifold gaskets.
6) Front crank oil seal.
7) Motor mounts.

Now if I had to do this in my garage without a helper (Except to help perhaps put the heads back in without damaging the head gasket.), cherry picker, and engine stand. I would have to weigh what this community said. Maybe you can do it engine in but maybe folks say its worth spending money to buy those tools to avoid frustration.

Curious what everyone says, in or out?

 

[Philip1]

Can I ask a side note? Did you pull the heads engine in or pull the whole engine? Need to replace my head gaskets and I'm trying to find more information either way and I cant really find any good videos. Maybe easier to start a PM with this...

If you have head bolts, you can pull heads with the engine in place but it is a tight squeeze. On the passenger bank, you will have to zip tie the rear most bolts up because they cannot be removed due to the ac box being in the way.

 

[79jasper]

You can definitely just pull the heads.
I've done a stud installation with engine in as well. Nothing is impossible, just harder/more time consuming.
Definitely have the heads rebuilt and machined, just make sure the shop knows what they're doing with these heads.

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[grizzlyjosh]

Thanks for the responses. I will pull out that other head as soon as I get a chance. And I'll take some pictures of the top of the piston that has a divot from the valve.
If bad exhaust valve guides is a know problem, would ya'll recommend replacing ALL the exhaust valve guides while they are in the shop? Should I be thinking of anything else? Lifters, while everything is exposed?

 

[79jasper]

Iirc, lifters are pretty robust in these. Only time I would upgrade is if I was doing stronger valve springs. (If running higher boost)
@IDIoit ran some fancy Johnson ones, I think.
Imo, valve guides are all in one. They require machining to do right.

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