last week was an expensive week 2 destroyed engines...
 

Just wanted to post this here and get some input...

I have a jet boat that i have had a nitrous/na 5.3 deal in for a couple years now. Its been running well but i decided i wanted to go twin turbo.

I bought a set of 72mm turbos, changed out the pistons, had the rotating assembly balanced and rebuilt everything... Specs are

5.2 block/stock bore
Hypereutectic dished pistons
Scat rods
Stock crank ground 10/10. I was NOT happy with the surface finish on the crank
Clevite P series bearings
Durabond cam bearings
BTR Cam
Melling 10296 pump, stock spring that it came with
LS3 Camaro pan with Bypass still in pan
Valvoline VR1 20-50 oil
and whatever else is needed

Fire up boat in the driveway and had perfect oil psi, idle at about 50psi. Came up to about 70 when i revved it a few times. Took it to the lake for a lake test

Boat ran great, didnt get into it to hard since it was a new engine, pressure stayed around 50psi all day long and just ran the boat around the lake. a couple real short blasts and that was it

Take the boat out the next weekend and run it for awhile, oil temp gets up to about 180 so i finally get into it. boat pulls about 7200 RPM and 15psi of boost. I notice that oil psi is now looking around 25psi.

I then babied the engine back to the launch ramp and could hear knocking.

Pulled the engine out and had 6 spun rod bearings.... I assumed this happened from the poor surface finish on the crank grind. (all clearances were great, about .002 on the mains and .0025 on the rods measured with a bore gauge and mics)

With the 4th of July around the corner, i hustled and slammed together a 6.0 i had tucked away for another project. Specs were

Brand new GM Crank that was re-polished (to get rid of some very slight surface rust from sitting)
Gen 4 rods, ARP Bolts
New Speed Pro Hypereuctic pistons
Same Melling 10296 oil pump (disassembled and cleaned)
Same cam/lifters/intake/heads/etc (Note: Lifters were disassembled, cleaned and inspected)
Rotella T4 15-40 oil

Engine went together very well, again all clearances checked out very nicely. Spun very smoothly by hand. Made sure there was 0 assembly lube on back of bearings/block/rods

Crank engine with no ignition/fuel for about 10 seconds and builds about 25psi of oil psi. Hook up ignition/fuel and fire and idles at 50psi, climbs to about 65 at 3k while im running it in driveway for a few minutes. All looks good...

Then engine looses oil psi, drops down to about 15psi and i kill it. After sitting for a minute i crank and verified there is no oil psi (by cranking and disconnecting a turbo feed line) i pull engine out and look at it. Bearings still look good, oil pickup O-Ring is good, Barbell and front plug are in block and good..

determine it to be a bad oil pump. So i put a NEW stock LS6 pump on and fire it up. Everything looks good, about 40psi at idle which is what i expected from the stock pump

Load boat up and head out to test. Fire it up and let it idle for about 15 minutes while waiting for my friends to get launched. Oil psi looks great about 35 at a hot idle (about 180* oil temp)

Take boat for a few trips around lake and everything looks good, keep RPM around 3500 for about 15 minutes.

Park boat and let things cool off, decide to go out again. Run the boat for about 30 minutes at about 3500, oil psi is about 45 while running, 30-35 at idle. Oil temp about 180 and staying there, engine temp about 160

I get into it one time and saw 6k rpm then backed out of it. It MIGHT have made 5psi worth of boost. And Bam... oil psi back to crap and oil temp starts climbing.

This time im pretty far out in the lake and takes me a while to get back to the trailer and had to run the engine in spurts longer than i wanted to. I pull it apart and All of the rod bearings are destroyed, #2 and #4 mains are spun, i don't remember for sure but at least 4 rods spun.

It looks like oil starvation, and it seems to be fine until the oil psi climbs up above 50-60 psi then it seems to go to crap. The only thing that i can think of this time around is the Oil Bypass Valve in the pan. Would love to hear your thoughts, could this cause the oil to starve from the mains/rods? FWIW I pulled the valve out after the second failure and tested with air (40psi) and it is stuck open.

My theory is that it opened up when the oil psi came above 55 (like its designed) then it got stuck open and starved everything.

If you read this whole thing i really would like to hear your input, and thank you! Irregardless here are some carnage pictures because we all like to point and laugh


https://cimg3.ibsrv.net/gimg/ls1tech...d8b2d55b43.jpg
https://cimg6.ibsrv.net/gimg/ls1tech...fa260086da.jpg
https://cimg8.ibsrv.net/gimg/ls1tech...06cf3e07a3.jpg
https://cimg9.ibsrv.net/gimg/ls1tech...cccd73cdcb.jpg
https://cimg0.ibsrv.net/gimg/ls1tech...46e26f6096.jpg
https://cimg1.ibsrv.net/gimg/ls1tech...fef128e3b0.jpg
https://cimg3.ibsrv.net/gimg/ls1tech...5fb2e8ed1e.jpg
https://cimg4.ibsrv.net/gimg/ls1tech...5246756b31.jpg

Damn dude that definitely sucks. How's the tune look? Any knock are anything recorded. Could be beating the bearings to death maybe? I don't know much about the factory oil pan bypass but I do know my buddy had 2 melling oil pumps have the relief get stuck open and destroy two motors within weeks of each other. Needless to say he doesn't run a melling pump anymore.

Its a Blowthrough CSU Carb deal. Intercooled and i run good fuel. Running VERY low timing (i think 14* at 14psi if i remember right)

Wideband showed on the rich side, and the plugs/pistons show 0 signs of detonation.

While i made this post i looked at the pictures again closer while im on a computer. And looking at the picture of the pan (below) you can see a clean spot coming (red box) from the bypass deflector that leads me to think that oil was continuously moving through here and not letting it sit/build up there like the rest of the pan

https://cimg4.ibsrv.net/gimg/ls1tech...08276d3507.jpg

Damn sucks!! Maybe a dumb question but how is the engine orientated in the boat? Forward facing or rear? Could the oil pump be cavitating under heavy acceleration due to oil moving away from the pickup?

Forward facing just like in a car... This exact combo ran for 3 years NA/Nitrous assisted.

I am REALLY leaning towards the relief valve.

I would look at viscosity of the oil your using. High RPM you could be starving the mains.

Rods are the last in line to get oil, so when they get toasted like that, it’s often a starvation problem. I would suggest making sure the oil passages in the crank are clean and to check pan to pick up clearance.

Checking the Pan to Pickup clearance is one thing i didn't do, mainly because this was the same setup and parts that worked successfully before.

What should the clearance be? How would one adjust it other than spacers? Wouldn't that cause a problem with putting the pickup into the pump?

I usually shoot for 1/4”” to 3/8”. You can pry the tube up for less clearance or hammer it down with a rubber mallet for more clearance. Either way, I do it with the pickup tube bolted down to the main cap and pump and it will usually go back on and the clearance will stay consistent.

Looking at your pics again, it really looks like the pickup is pretty far forward in the sump. It might not be staying submerged in the oil if the nose of your boat gets pretty high. With the extra oil demands of the turbos, the oil level could be lower now and causing problems that weren’t happening when it was a nitrous combo.

I do have a diverter and a decent pump, on a launch the boat stays pretty flat. Maybe a little up in the front...

Not to mention i havent even attempted a "pass" yet with the turbos. Everything has been from a roll if you want to put it that way

I did think i might be running somewhat low on oil. Im running 8 quarts. I plan to add atleast another quart this time around. Im running -4an feeds and -10an returns. Return flow is pretty straight forward, feed lines are maybe 4 feet in total between the two. I dont know how much oil the turbos can hold?

This is one reason that I won't run a pan with a bypass in it. The oil was a little thick for the bearing clearances, but not enough to do this.

Its the only thing that will fit.... you better bet your ass when it goes back together its getting plugged lol

I Had a similar situation with my LS3. Lost oil pressure and wiped out all the mains. One rod is a bit worn, but all the rest are good. I came to the realization I may have installed the pump wrong. Just curious if you might have done the same?

I saw you used P bearings on the 5.3L

What bearings did you use on the 6.0L?

P's also.

I believe the factory uses an A bearing on these engines.

Just speculation, But I have seen enough clevite p bearings bearings fail on these LS engines that I personally believe they are too soft for this application.

I am planning to switch to King bearings with the rebuild. I dont think that was the complete cause of the failure but it might have been a contributing factor for sure.

No so much the brand but the bearing type.
I have seen Junkyard factory bearing engines beat to hell and the bearings look great. Put a P series bearing and they dont last a few hundred miles.

Obviously things like the relief valve sticking and so on play a factor as well but Something about P series in these LS engines just don't seem to work well from what I have seen.

I bent 2 rods with a 20+ PSI boost spike and all the factory bearings on the 100K mileage engine and they still looked almost new. I replaced the 2 rods and pistons and reused the factory bearings on their respective journals.

Im looking at the XP Series King's that are tri-metal. Do you have another recommendation?

I have heard the King Brand is good but I have no experience with there stuff. Sorry I couldn't be more helpful.