Odd SBC thing...

Ovid_and_Flem just sent me this vid. These are .030-over aftermarket pistons in his Challenge Vette. They shouldn't be loose like this, right?

Regardless I'm pretty sure this is the source of the noise we've heard!

Those are either the wrong size, the oval in the skirt is wrong, or you have a video of a classic collapsed piston.

That would rattle like a worn out Neon.

Yep. That would make all kinds of noise. Time to get out the measuring tools and figuring out what is what.  30 over pistons in a 60 over block?   

In reply to Streetwiseguy :

I forgot to mention that all-8 pistons are doing this...

Time to measure. If they are new, I'd guess they were labeled wrong. That looks more like a STD piston in a .030 hole to me. 

Thanks, we'll check piston & bore size then determine the plan. 

There's gotta be more to this story. Like said above, looks like a std. piston in a .030 over hole or .030 over piston in a .060 hole. 

I've either provided the new pistons or bought new from the machine shop... but they were all fit at the time of machining. Or, was the block already bored when he got it? Regardless, that shoulda been caught before installing the first piston. Mics and dial bore gauge time.

So, what's the rest of the story?

Just figured it out - whoever rebuilt it had even less of a clue than me: .030 pistons in .060 bores...and stock rod bearings on a turned crank. :-/

The story is he found it behind a building abandoned - after being damaged by a tornado - and got it for $500. Looking it over it appeared to be a fresh rebuild. No leaks, clean, new torque converter...it was just rebuilt by an idiot. 

Maybe it rattled, which got it thrown out behind the building...

That was my conclusion when i was on the phone with jim after he sent me the video, and he was getting a measuring device to verify.  Luckily for him sbc parts are ridiculously cheap.  

How this motor ran as long as it did or not even have a major rod knock is amazing.  Every thing was so loose.  The rods bearings were so loose you could move the a visible 1/8 inch.

Now gotta decide what we're  gonna do 32 days from challenge.

How does the crank look?

Mic crank. Order correct undersized bearings, .060 hypereutectic pistons are $80 from summit and some cheap name brand rings and slap it together.  I probably have some .060 rings in my stash.  Only part needing professional attention is swapping pistons on the rods because press fit pins.  Measure rod length 5.7 or 6.0 to make sure which ones they used.  

How this motor ran as long as it did or not even have a major rod knock is amazing.  Every thing was so loose.  The rods bearings were so loose you could move the a visible 1/8 inch.

Abbreviated back story:  car was purchased not running as it had been damaged in a tornado while it was in a shop for tune up.  Litigation ensued between car owner's insurance and shop owners companies.  It sat for 2 years.  It had been traded to a subsequent owner who never did anything to it.  Owner I got it from was told engine had been totally rebuilt shortly before it was in tornado.  Upon tear down after it developed an intermittent tapping noise reveal it obviously had been rebuilt...new pistons .30 over, fresh bore job .60 over apparently, fresh valve job etc.  Motor was immaculate and fresh only problem is miss mash of new but wrong parts.

Now gotta decide what we're  gonna do 32 days from challenge.

A fleeting thought is to find some peckerwoods with a crash dirt track car I can buy long block from, transfer my accesoriis to.  We shall see.  Have an offer to buy reasonably priced LS1 5.3 but parts to make it fit and time crunch prohibitive for challenge.

I have to wonder if somebody was planning on drag racing this engine and thought that building it "loose" would increase power due to a lack of friction. Check the cam to see what the duration and lift is

In reply to mad_machine :

That thought crossed my mind but ad best I've been able to surmise car was some middle aged guy's  cruiser...still has stock L98 roller cam.  Original numbers matching engine a 200k mile 89 c4.

That's a lotta 'loose'. Did cruiser guy have it punched out and assembled it himself... only w/ the wrong parts? 

Sounds like it's salvagable by replacing slugs and bearings if it wasn't run much, hopefully the bearings took the brunt and not the crank. That could just be a cut away anyhow.

In reply to fasted58 :

It appears rod journals were turned but bearings were standard.  Like I say it's crazy how this motor was assembled. Rod bearings were all spun.

Positive original owner was not a DYI guy.