Are my pistons still good?

[djgeque]

I ripped off my head after finding a bolt in my intake port (it didn't fall into the engine). I had no compression in the left cylinder. The cylinder wall look extremely smooth no scratches at all. However the piston head has marks on it from where I suppose the valve hit the piston.

The head is being rebuilt but I would prefer not to rebuild the bottom end if at all possible. What do you guys think?

Thank you!!

 

[jamaral]

Well something been rattling around in that jug for awhile now. Possibly even another bolt or metal pieces...what does the head look like? Are there dents all over the valves too? Me i would replace the piston with a n.o.s. piston, lightly hone the cyclinders and new rings for sure.
Good luck

 

[nj1639]

There is a spec for the connection rod tolerances to be found somewhere in this forum. I would check the tolerances and if in spec I would throw her back together and run.

 

[tonyc]

dj the pistons and rings is still considered the top end. If it were mine and if I could afford it I would replace the pistons.

 

[djgeque]

I would love to replace the piston but I don't have the best budget for it. I would prefer to replace it later if possible. I am also finding it very difficult to find NOS pistons and rings for a 72 engine. The only ones I can find are over sized. If anyone has any luck with this please let me know...

The head looked fine but the machine shop said both my intake valves were bent and the exhaust on the damaged side was bent as well. What would happen if I ran it as is for a while? Would I be risking performance or further damage?

 

[Paulrxs650]

If you've go bent valves you need to sort tem. From the photos that piston, whilst not ideal, is still serviceable. So, in your shoes id use the money, to sort your valves out

 

[grizld1]

I love you guys, you're a laugh a minute --any of you ever hear of micrometers and bore gauges? They have the good stuff at automotive machine shops and charge from nothing to the next thing to it to give you the specs on jugs and pistons so you know whether you can get away with a hone job or not with a given piston; and BTW best practice is to have the bore and the individual piston you plan to use miked out together, so you know what the clearance is.

But I understand--real men roll the dice and use their eyeballs.

 

[sethhazuga]

I love you guys, you're a laugh a minute --any of you ever hear of micrometers and bore gauges? They have the good stuff at automotive machine shops and charge from nothing to the next thing to it to give you the specs on jugs and pistons so you know whether you can get away with a hone job or not with a given piston; and BTW best practice is to have the bore and the individual piston you plan to use miked out together, so you know what the clearance is.

But I understand--real men roll the dice and use their eyeballs.

Any time I see this in my shop, I would tell you what I'd tell my customer.
quote: there is damage. there is a chance this could work, but not the route I'd go down. at min. new valve cut job, guides, and valves, but I can't gurantee the work if we are going to do half the job.

 

[hotdog]

any of you ever hear of micrometers and bore gauges?

Obviously not....

 

[scabber]

That piston needs to be replaced all those sharp edges will probably cause detonation once they heat up. Its pay me now or later. My opinion. The cylinder looks damaged also.

 

[nj1639]

dj the pistons and rings is still considered the top end. If it were mine and if I could afford it I would replace the pistons.

Yes, the bottom end infers everything below the jugs in my book so the question about tearing into the bottom is why would you? and then asking about using the piston is like "Huh?".....if the head is being rebuilt. Terminology and assumptions.
I'd run that piston if it was the last one on earth, after cleaning it up and after having the bores and rings checked.

Save your money and do it right.

 

[grizld1]

Exactly, scabber; and the hammering that piston took near the edge may very well have distorted the top ring groove.

Re. bent valves--they have to be replaced, and the guides were likely damaged by them. The inspection procedure is in the factory manual, the manual is free at www.biker.net , and there's no sense repeating it here. Either way, dj, you're in for a valve job.

The bottom line is that you're not looking at a cheap and easy fix. If those gouges in the bore are as bad as they look in the picture you're probably in for a bore job to 2nd oversize, and that means replacing both pistons, not one.

Good luck to you.