piston damage (new pictures)

billfish

billfish

Senior Member
piston damage (new problem)

While doing valve job on my 51 8ba I discovered this damage to #6 piston. It was not there 10 months ago when I had the head off. Never heard anything and the compression was good when checked before I took head off. Looks like a small piece broke off piston top edge and bounced around before being ejected. See attached picture. Not looking forward to dropping pan and removing piston to examin. Any ideas?
 

Attachments

  • IMG_0360.jpg
    IMG_0360.jpg
    91.8 KB · Views: 395
Last edited:
Re: piston damage

like the others, my guess is a broken top ring, I wouldn't run the engine any more till its fixed
 
Re: piston damage

What does the wall look like?? That does not look exactly like the broken ring problems I have seen over the years. I wonder if something came from a valve or port or through a valve and port? I guess anything is possible so it is good that you have the engine apart and can get it reviewed.
 
Re: piston damage

Sure looks like the the mark on top of the piston was made by whatever was (forced ?) out of the hole on the opposite side. It's a mystery.
 

Attachments

  • ring.jpg
    ring.jpg
    190.9 KB · Views: 241
Re: piston damage

picture of cylinder head--cylinder wall looks clean with a couple of very slight vertical scratches on the bottom side where it corresponds to the piston damage. this does not show up in a picture.
 

Attachments

  • IMG_0370.jpg
    IMG_0370.jpg
    69.6 KB · Views: 298
Re: piston damage

Cylinder head looks as one would expect it to look considering what happened, but no matter how one tries to get around it, the engine should be dismantled to properly check and correct the problem.
If left as is, there is the possibility you could loose the whole engine.
 
Re: piston damage

This is a classic long term broken ring result. When the piston is pulled the ring groove will be well hammered as previously stated , by other people.
 
Re: piston damage

Had that happen to me back in 1964, when I drained the oil I found broken rings in the pan.
 
Re: piston damage

Thanks for all the advice, I will drop pan and remove piston next week and report back to you with the results and pictures. In reinstalling the valves I'm having a problem pulling the intake valve guides down to install the horseshoe clip. The rubber seal around the guide is the problem, even with the proper pry bar they won't budge, any tricks I could try. Maybe i'll start a new thread.
 
Re: piston damage

I don't think you will find a broken ring that caused the damage.the more it is looked at it looks like foreign object damage (fod)

R
 
Re: piston damage

billfish said:
Thanks for all the advice, I will drop pan and remove piston next week and report back to you with the results and pictures. In reinstalling the valves I'm having a problem pulling the intake valve guides down to install the horseshoe clip. The rubber seal around the guide is the problem, even with the proper pry bar they won't budge, any tricks I could try. Maybe i'll start a new thread.
Click to expand...

You can try a little lube on them, or just use rtv instead of the seals.
 
I like the idea of the RTV is that an acceptable substitute for the rubber seal.
 
Last edited:
Re: piston damage

RTV will work just fine. I think if you had a broken ring, the bore would be pretty well scratched up
 
Re: piston damage

billfish said:
I like the idea of the RTV is that an acceptable substitute for the rubber seal.
Click to expand...

Only on the intakes, I think the exhaust would get too hot.
I just pulled apart a 350 I did ten years ago, had rtv on the intake manifold ends instead of gaskets. Was still holding just fine with no leaks.
 
Re: piston damage

Recently had a top ring break. Heading for a car show when all of the sudden I got a rattle sound from the engine. Shut it down, had AAA carry the truck home. Same damage as you showed on top of #5 piston. Pulled the piston and found the broken ring, Just went ahead and replaced all the pistons while I had it opened up.
Good news, no cylinder damage. Sad news is that when I had my machinist do some work for me 5500 miles ago he said that the piston were "about" ready to need replacing. Well no $ put that on hold...Guess what now I have new pistons, rings, gaskets and a "woulda, coulda, shoulda" moment to add to the list.
Those horseshoe clips are a "learning experience". get the claw on your bar to catch the lower portion of the valve guide. Push up on the bar just enough to expose the clip groove and get the clip started in the groove enough to get the valve guide to remain visible. Then gently tap the tab on the clip with a small hammer. It should slip into place and seat in the recess. Because my hands are size 90 and the space size 10 I use a long pair of needle nose pliers to initially maneuver the clip into the slot. You'll get it.
 
You must log in or register to reply here.
Back
Top