930 rebuild in progress.......I need your help and opinions on the mess inside
 

Engine has 34 hours since complete build. Power was down, so we did a leakdown: 40% on number 3.

So the engine goes into the shop for a look-see.
Gets worse the further we look - first is the burnt valve, no big deal. Then the shuffled heads and the gouges on the cylinder tops. Uh-oh. Then the scoring on the cylinder walls.

Can these cylinders be saved? They were brand new 34 track hours ago.
http://forums.pelicanparts.com/uploa...1148837443.jpg

http://forums.pelicanparts.com/uploa...1148837459.jpg

http://forums.pelicanparts.com/uploa...1148837499.jpg

http://forums.pelicanparts.com/uploa...1148837548.jpg

http://forums.pelicanparts.com/uploa...1148837568.jpg

Cylinder and heads:

http://forums.pelicanparts.com/uploa...1148837636.jpg

http://forums.pelicanparts.com/uploa...1148837682.jpg

http://forums.pelicanparts.com/uploa...1148837705.jpg

#3 and #5 had broken top rings, yet scoring is on nearly all the cylinders

heads can be flycut and cylinder tops can be cleaned up in a lathe, but the scoring suggests a new set of P+Cs is in order. and limit your boost in the future. it's been blowing past at least one head for a while too. no broken studs? maybe everything is not on the same plane. maybe swap the all-threads for something better.

you might want to go a bit deeper and check the rod bearings too, considering the detonation issue that broke the rings.

No broken studs. Has fully threaded studs that are non-magnetic (dilivar?). ARP will replace the threaded units. 'Fire ring' (slots cut in heads and cylinders) will help to locate the heads to the cylinders and help prevent blow by -

The boost has been a stock .8 bar since the initial build.
If the pistons were installed 'backwards', would it cause this scoring?

Those pistons look like they are higher compression than the stock ones. What compression ratio were you running?

Curious...did the pistions get fouled after the rebuild? Were all the carbon buildup cleaned before assembly? Nothing to do with the post, but just wondering if it can get that dirty only after 34 hours?

I would pull all the studs out and measure them- they all should be the same length, if not, they should be replaced. I also suggest against an all thread stud here- too rigid. As far as the cylinder faces, I would have them surface ground rather than decked in a lathe, but I would replate the cylinders and have them cryogenically treated if you plan on re-using them before having that done. I'd be willing to say that you've toasted them and you'll never get any kind of longevity out of them. Flame ringing also wouldn't be a horrible idea the second time around.

As far as the pistons being installed backwards, I don't think you can- the JE's don't have offset pins. The scuffing could have come from the piston heating up real fast and out expanding the cylinder. Coated skirts help that to some extent, but the coating is sacrificial so it won't last forever.

Almost looks like that one valve has a pre-burn slot in it? I'm wondering (especially with the broken rings) if you weren't detonating...

Are you sure you were running .8 bar boost? How about fuel? Was it quality? Ask Steve at Rennsport what he things about most fuels these days...

Bottom end.
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#6 cylinder -
Caps
http://forums.pelicanparts.com/uploa...1149892434.jpg

Bearing shell
http://forums.pelicanparts.com/uploa...1149892466.jpg

Other side of shells. THE ugliest thing you want to see on a 30 hour engine.
http://forums.pelicanparts.com/uploa...1149892518.jpg


Will be 'interesting' to see what the other bearings look like.

Craig,
You did a teardown a right right time. Anymore on that engine would have been catastrophic. The crank mains and journals will tell a lot too.

Other than the lost of power, what else did you notice that led you to believe that there was something seriously wrong with the rebuild? (i.e., strange noises?)

Noticed a loss of power late last year
Checked timing and mixture - both were fine.
Did a dyno run in December - down 56 hp.
Checked leakdown - 40% on #3 through the exhaust.

It will be interesting to see what the root cause is here... that thing looks like it has been through a war!!

All the best, Craig,


JA

Those are some ugly bearings , glad you caught it!

Ughh - I had a failure on a "pro" built engine years ago because the crank was not cleaned property. I should say spectacular failure since the rod went thru the case and it was in a race...

Have you noticed higher than usual oil temps?

I'm confused as to how this engine has 34 hours on a "complete rebuild". Those bearings look so ugly. I guess this is your track car? I don't race, but I wonder what 34 hours of race time traslates into street years...sort of the 7 dog year conversion. It looks worse than my engine that had never been a part in close to 20 years. I guess when things start to go bad in a turbo engine...they go bad real quick like!