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Damaged Pistons - Need Advice

greedyg76

greedyg76

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OK to make a short story shorter, I just finished rebuilding the 350 in my 76 K5. 50 miles on her running sweet, then within 20 seconds a little ticking noise turns into a loud hammering. I shut it down and coast to a stop. When I tear it apart I have 3 of my brand new hyperutectic pistions all nicked up from what appears to be a small bolt.:mad: The cylinder walls do not have any scratches. Should I replace the pistons or throw it back together and run it? Keep in mind it almost broke me to rebuild this motor in the first place so I am on a very tight budget.

I will post some pics here shortly

HPIM4544.jpg

HPIM4548.jpg
 
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You could probably put it back together and run it, pretty unlikely that the pistons will fail IMO.

Other people will probably disagree but I've seen people run much worse.
 
I concur... money and time, do it right... otherwise, it'll run... as long as the valves are ok..

btw, looks like a bolt to me...
 
Yes there is damage to those pistons but nothing bad enough to worry about. I suggest carefully dragging a file across the top of those pistons to remove any sharp areas that would create a hot spot and promote detonation to start. Even a piece of emery cloth or something, just make sure there are no sharp or pointy areas. You also need to figure out where that bolt came from and make sure there aren't anymore screws/bolts in the manifold anywhere that could cause this disaster again. Further more, the valves that the screw had to go through could be bent and or the seat damaged so take the heads into a shop and tell them what happened and have the heads checked really close. Also lay your pushrods on a piece of glass and roll them to make sure there aren't any bent ones.
 
If it were me, I'd replace the pistons. But thats just me. I would be paranoid about it comming appart on me. But as stated above, clean up the sharp edges and run it. I'd be best to pull the head appart and check for bent valves too. Look for knicked up edges on them also. If you can twist the valve while it's in the head...then it isn't bent. Roll the pushrods to check for straightness. It'd also be a good idea to pull the lifters and take a look at them. I've had one break in half when a valve got hung open. If you find a lifter thats bad, you might want to think about replacing the cam. I doubt that you'll find a broken lifter though, since a pushrod or valve usually bends first.
 
How did it happen to MULTIPLE cylinders?

BTDT, luckily (or not) the piece got stuck at the valve. But it was only one cylinder.

Have you contacted the piston manufacturer to see if they sell individual pistons? As cheap as hypers are (still around $120/set?) you'd think replacements would be pretty affordable, IF you have any money to do that.
 
Crap can enter through one cylinder then get sucked back into the intake and go into other cylinders as well.

Pistons can be bought single and usually cost around $20.00-$30.00 each. Rings however can only be bought in a full set. Most times though you can remove the rings and re-use them.
 
dyeager535 said:
How did it happen to MULTIPLE cylinders?
Click to expand...

That is the same question I am asking myself, but the dents on the pistons are exactly the same size and shape. Which means 3 identical looking pieces fell into the intake at the same time (read SABOTAGE) or one piece bounce in and out of 3 cylinders and I dont know how that is possible...
 
Read my post above. Stuff that gets into the engine and eventually into a cylinder can work its way back through the intake and into other cylinders. I see this stuff on a day to day basis here at work.
 
scott would know as he builds motors.

but my question is were is the head of that bolt? kind of funny unless you were vary careless or someone put it in your intake to get back at you.
 
4X4HIGH said:
Read my post above. Stuff that gets into the engine and eventually into a cylinder can work its way back through the intake and into other cylinders. I see this stuff on a day to day basis here at work.
Click to expand...

Yes, I read your post. I just don't see how that could happen with the dual plane Edlebrock intake manifold Im running. For that bolt to go from the cylinders on one side of the engine to the other side, it would have to be spit back thru the intake valve up the runner, up into the carb past the butterfly and come back down the other side of the carb to the other cylinders. :confused:
 
I would do as Scott 4x4 high recomends. The pistons are not that badly damaged.
File or emerory cloth them. Check the valve train for bent parts or damaged valve seats. If everything checks out Run it.
I have had similar happen to motors. Cleaned them up and they were fine.
 
OK, I was just thinking and I just came up with something.

On that Edelbrock manifold, one plane feeds the front and rear cyls on one side and the middle two cyls on the other side right?

If so that makes sense because my F'd up pistons are #'s 8, 3, & 5. Those would all run off the same plane of the intake.

Thanks to 4X4HIGH for forcing me to use my brain...:bow:
 
What do the heads look like??? I would be just as worried about the heads/valves.
 
It's a miracle he didn't wipe out a valve or seat...
 
The heads and valves, being harder steel than the pistons, hardly have so much as a scratch. Before I tore off the heads I did a compression and leak down test on all cylinders, cycled all the valves and tested again, both resulting in good numbers. So the valves and seats look go to go. Guess I'm lucky
 
Like i said earlier, i highly recommend you take the heads in to a shop and have them checked. I've seen enough of this type of damage and it almost always ruins a valve seat and a valve. :deal:
 
HAA!!!... The exact same thing happened to me when I put my 350 in my 85 Blazer. Except it was a washer. Same noise and everything, couldn't figure out what it was for the longest time. I even work on my truck by sitting in the engine compartment like in your picture, and I thought I was the only one!!... I ended up just replacing my piston. I checked my valves over, just eyeing them, never took them in for an inspection (not saying you shouln't) but I didn't. I had/have the same edelbrock intake as well. 60,000 miles later still runs strong. compression numbers still look good. Do what you think is best, but sounds like you got lucky like I did....
 
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