NO! What does the bore look like?
 

Dixon’s busted FE.
Only thing I can think of is ring compressor damage during install, if it was one of those type that have a corrugated type clamp surface?

John, what did you use?

That's a strange one.  The pattern doesn't look like one seen when the piston scuffed.  That looks like a lot of straight lines very close together and you'd see evidence of it on the piston skirt as well. 

If the bore is relatively smooth I'm inclined to believe that its some kind of installation error/damage. 

One thought is that there wasn't enough back clearance between the ring and piston.  This can also cause scuffing and damage even if the PTW clearance was right, and the ring endgaps were right. 

That was caused by ring flutter.  Basically, that ring is too small for the gap in that piston.  It moved up and down in its groove and at speed, the harmonic vibrations caused that ring to lift off the bore and hot gasses of blowby ate those marks into the ring.  It had to run like crap, have a lot of backpressure, and used oil like nobody's business.  Are all eight.like that?

Will be interesting to see if the rings on the piston you have match the marks on this one.

I am getting ready to do forensics on Al’s kaput 351 when he brings it down to me.  You guys know how I like to inspect every tiny detail to see what could have caused his engine to lock up.

I though those vertical ring marks were very odd.

Gaba wrote:

wait Al's Kaput 351???? the one he just put into his car? ( like 2 years ago)

 
Yeah, he took it out to WRING IT OUT A BIT and now it is seized up.

But don’t let that worry you.  Yours will be fine!

Jeezz...I go ring out the Heap a little and it eats the main bearings after over 30K of doing just fine.  Now Al's new (unrelated) 351 seizes while he's "ringing it out a bit".  Gotta be some kind of conspiracy.  Sorry to hear about that, Al.
 

Last edited by Bullet Bob (2/09/2021 4:02 PM)

Why do the cylinder walls not show much cross hatching from honing?

What's concerning about the cylinder is that the vertical lines travel all the way to the top of the bore.  If these were caused by a ring issue those lines should stop short of the top.  There's always an area at the top of the bore that's out of ring travel.  Typically you find a dark ring at the top of the bore, and can sometimes find a ridge there from the rings wearing the area below it.  To me this looks like marks from the boring bar that weren't completely removed by the hone.

Obviously there was something wrong in cylinder #5.  That skirt shows serious damage.

Crosshatch, for what its worth, is a misunderstood metric of bore health.  I've never seen an engine where you couldn't still see at least some of the cross hatch.  Maybe years ago when chrome rings were a thing the rings would chew the crosshatch completely out of the bores as the engine wore out, but with modern rings every engine I've ever torn down (including ones that had blowby) always showed some crosshatch.  When you get a freshly honed block back the crosshatch should be barely visible, if at all.  Honing a bore is like honing a knife.  If you look at the edge of a knife under a microscope as you sharpen it you will see little fingers of metal appear.  The final honing and stropping aligns al those finger towards the cutting edge center line.  This is the same with a bore.  After the hone all the fingers are laying in there homes.  When the crosshatch becomes evident its because the rings have torn those fingers out of the bore wall.  Smokey Yunick devoted three pages to discussing bore prep in his book, and he investigated it thoroughly, including cutting blocks up and looking at them under a microscope.  As I read it I got to thinking and it caused me to change my thinking, which had really just been using "common knowledge".  Bottom line, you can't tell much just because you can still see the crosshatch.  There's a lot of other things that can still be wrong with the bore (out of round, taper, wasn't bored with a torque plate, etc.). 

Back to your engine, I'm wondering if everything was checked when it was assembled?  Who did the assembly?  I'm wondering if the machine shop made a mistake with respect to PTW clearance, or if there was a mismatch between the rings and pistons.  Were the parts purchased individually or as part of a kit? 

The rebuilder didn’t the first assembly years ago. I did the assemble after I swapped the crank and had it balanced. The machinist reported the PTW clearance was good. The busted crank was the major player in how bad that one piston looks. 

Mike, that’s a sad story. 

Last edited by Bolted to Floor (2/11/2021 10:10 AM)