A specifically wrong thread...

[canyncarvr]

..as it deals with a 'Non Mopar technical' question. If that's verboten, I guess the thread will get 86'd.

I am asking for input of a technical nature on a non-Mopar engine. It's my nephew's. The problem could likely be seen in any engine if the cause was present. I don't know the cause and am asking for forensic opinions.

It's a Vr6. The short block was assembled at the machine shop. It was a basic rebuild: Bore, hone, new pistons, resurface (head for sure...deck I don't know). The engine fired up, was run for 20 minutes at cam(s) break-in speeds. A compression test was done (engine owner suspicious of engine smoothness) to find only one cylinder where it should have been (160psi) with the others 65-80psi.

A leakdown test showed the valves were OK...pressure going past the rings. On disassembly, one broken oil ring was found. A Vr6 is rather known, evidently, for breaking rings on install 'cuz the piston is angled to the block deck. Again, the short block was assembled at a machine shop.

The kid spent a lot of money on this thing. Like any aficionado, more coin than any other-brand fan would consider sane. Any help would be appreciated.

Depending on type, rings could very well NOT seat with a 20 minute cam break-in run. The one cylinder with good pressure kind'a blows that idea (no ring seat) out of the water.

The main concern is the rod bearings. He said he can FEEL the aberrations with a fingernail. The rod cap bearings are OK.

For the forensic part: I'm sure these rod bearings tell a story, but I don't know what it is. It looks to be something other than FOD. Maybe not. He did find some metal bits in the head the shop hadn't cleaned out.

Any conjectures would be appreciated.

Thanks!

 

[TrailBeast]

..as it deals with a 'Non Mopar technical' question. If that's verboten, I guess the thread will get 86'd.

I am asking for input of a technical nature on a non-Mopar engine. It's my nephew's. The problem could likely be seen in any engine if the cause was present. I don't know the cause and am asking for forensic opinions.

It's a Vr6. The short block was assembled at the machine shop. It was a basic rebuild: Bore, hone, new pistons, resurface (head for sure...deck I don't know). The engine fired up, was run for 20 minutes at cam(s) break-in speeds. A compression test was done (engine owner suspicious of engine smoothness) to find only one cylinder where it should have been (160psi) with the others 65-80psi.

A leakdown test showed the valves were OK...pressure going past the rings. On disassembly, one broken oil ring was found. A Vr6 is rather known, evidently, for breaking rings on install 'cuz the piston is angled to the block deck. Again, the short block was assembled at a machine shop.

The kid spent a lot of money on this thing. Like any aficionado, more coin than any other-brand fan would consider sane. Any help would be appreciated.

Depending on type, rings could very well NOT seat with a 20 minute cam break-in run. The one cylinder with good pressure kind'a blows that idea (no ring seat) out of the water.

The main concern is the rod bearings. He said he can FEEL the aberrations with a fingernail. The rod cap bearings are OK.

For the forensic part: I'm sure these rod bearings tell a story, but I don't know what it is. It looks to be something other than FOD. Maybe not. He did find some metal bits in the head the shop hadn't cleaned out.

Any conjectures would be appreciated.

From the sounds and looks of it the shop that assembled it wasn't careful enough or clean enough on assembly.
A rebuilt bottom end doesn't come home with bearing surface scores.
Rings don't just break on break in, so I don't see how it could be blamed on it by a shop.
Though it wouldn't surprise me if they tried.

Take it back and make them go through it again, or return his cash so he can get it done right.

 

[brian6pac]

I don't see how a broken oil ring could cause low compression, I would look further.

 

[magnumdart]

On a simple rebuild I would expect the rings to seat almost instantly.
The broken oil ring is a sure sign that somebody wasn't paying attention to detail.
The pieces of metal in the head is beyond comprehension.
And that bearing looks like it could have clearance problems. Hard to tell on my cell phone.
It needs a do over. And I would check the crankshaft too.
Was anybody there to witness the initial fire up?
I wonder if they even bothered to prime the oil pump.
Just my $.02.