Piston Opinion Needed

[S30Driver]

There is a tempting deal not too far from me on a complete rebuilt short block from a 78 Z.

 

I am considering picking it up to replace my tired current motor until I rebuild the F54 turbo motor I kept from one of my other cars.

 

It apparently has less than 2000 miles on the rebuild.  The seller built up an F54 with flat tops & kept his head.

 

The pistons, from the pictures are dinged up, and are what concerns me.  Is this a major problem, will it cause any issues?

Any idea of what could have caused it?

 

Its only 90 miles away from me, is cheap, and if it is indeed a fairly fresh rebuild - new timing set, rings, bearings, etc. looks like a heck of a deal.  Any opinions appreciated ...

 

 

 

 

[Captain Obvious]

I'm no engine builder, but I'd have a hard time closing that thing up knowing I had pistons that looked like that...

[Patcon]

I wonder what caused the damage. Can detonation cause that kind of damage? I wouldn't be so worried about the little marks, the big gouges with the sharp edges might glow and cause problems. Not sure about that.

[S30Driver]

You are right Charles, that's what I'm worried about.

[siteunseen]

Your second picture looks like one of the pistons out of a boat motor I locked up. Pieces of the rings gouged holes like that.

[rossiz]

depends on the price... if you replace the pistons and can use all the rest plus already have clean bores, good bearings, timing set, etc. then you'll be into it for the cost of pistons (flat tops!), rings, gasket set and your time. if it's cheap enough you may be in a good spot.

 

the first worry i'd have is if the pistons hit hard enough to over stress the rods - hard to tell on that one. and if it was a stock '78 with an n47 head (domed) there would have been some pretty large objects in the chamber to do that (dropped valve?) which would have beaten the head up just as much...

 

the second worry i'd have is what kind of job was done on the re-build if they went through all that trouble and didn't replace those tatty-looking pistons... or did the damage happen after the re-build, in which case what kind of job was done on the re-build to allow that damage to happen??

 

but again if the price is right and you've got the time you might score a fresh bottom end with a bit more poke than your current setup.

[Zed Head]

I've seen a few threads about detonation and those small marks that look someone used gravel as shot to clean the pistons are typical of the marks detonation leaves, apparently.  Detonation can break rings so you'd want to pull the pistons at least.  Not a throw it together and go short block, I'd guess.  The big gouges look like foreign object damage.  

 

I've also seen in a small block chevy motor that hydrolocked, that when the connecting rod bends sometimes it twists.  A piston was twisted in the bore.  You might put a straight edge across the top and see if all of the piston notches line up.

 

Looks like it has some good parts though.  A 3 pulley damper, new water pump, good front cover.  Might be worth parts alone.

[madkaw]

I couldn't put it together with those pistons - especially when flat tops are pretty cheap. If that motor didn't detonate before, it probably will from all the hot spots created by those pits.

[26th-Z]

Do ALL the pistons look like that? The small, evenly spread out pits are from detonation which is not good. The big chunks and divots are from something broken (like a piston ring). Either way, those pistons are junk and you are just asking for trouble by using them. The bore clearances couldn't possibly be within tolerance and with the damage you are showing on just the one piston, I would expect the piston to break at some point in the future.

[S30Driver]

Thanks for the responses, confirming some of my worries, and the suggestions.

It's a $100 deal ...

Hear are the other pics

 

 

[siteunseen]

I'd pay $100 for that.

I've spent $100 on some things I don't even remember the next day. LMFAO!

[Patcon]

I think I would give $100 for that, even if I had to buy flat tops. Go through it. I would probably disassemble it and check it all then buy what I needed.