Hydraulic'd engine - bent valve or bent conn rod?

[Alex_M]

Hey all! Hopefully one of you can chime in and confirm or deny my diagnosis.

2002 6.0. Just installed a ton of new parts - heads, cam, lifters.... Injectors.... Allegedly "genuine" AC Delco Made in Germany. Well upon closer inspection after the fact, they shipped from China. Fake Delco injectors.

Anyway - got the engine back together and running. Was smoking some so I shut it down. When I started it again it started to crank, kicked, and stopped dead. One injector had leaked down and filled the cylinder with fuel. Pulled plugs, cranked over fine, cleared out fuel. I reinstalled the original injectors (so much for being proactive) and restarted the motor. I now have a ticking.

I am familiar with both bottom end and top end noise. This one is odd, somewhere in-between, but seems fast for a top end noise. So here I go, crossing my fingers for a bent pushrod. Pulled valve covers and no such luck - all good. Started with valve covers off, nothing obvious. Noise is no louder.

Here's the kicker. I did a compression test on all 8. 7 of 8 showed 175-180 PSI. Cylinder 3 which was full of fuel showed 150#. All 8 were leaking off at roughly the same speed, nothing wildly out of line.

So, here's where my logic goes. If it were a bent valve, it would either leak down much faster or it would show zero compression. Since cylinder 3 leaks down at the same speed but shows lower compression, that rod is most likely bent.

By the end I will at a minimum pull the head and check the valve as well as measure piston to deck height to confirm diagnosis, but in the mean time I'd love input on this, possible alternatives. Thanks guys

 

[OR VietVet]

You said, "When I started it again it started to crank, kicked, and stopped dead". That statement, if you said it correctly, says you did not start the engine, it says it stopped dead while cranking the engine. If that is correct, then I suspect that you have a damaged flex plate. Happens when you have a cylinder full of fluid, try to crank engine, offending piston gets close to TDC, the fluid does not allow any further movement and kicks back at the starter drive and then the damage gets to the flex plate and causes a crack. I have seen the nose of the starter break off completely as well, so if I was you, I would remove starter to inspect for breakage or cracks and inspect the flex plate thoroughly.

By the way, change the oil and filter too.

 

[Alex_M]

Ah! Didn't even think about flex plate. I will certainly inspect that. And yes, the engine did not actually start. Felt like it tried to light off before it was stopped, but... Obviously didn't.

However, do you have a theory for why the compression would be showing so much lower on the cylinder that hydraulic'd?

I do not think it's because the cylinder was washed down with fuel, because I drove the truck 3 or 4 miles doing testing earlier in the day before the compression test.

 

[B-train]

Since it was spinning and abruptly stopped due to hydro-locking, you most likely have a bent connecting rod. It doesn’t take much for it to happen with the rotarirng mass ans the high torque of the starrer. Your compression is lower on that cylinder because the piston isn't traveling as high in the cylinder due to the shortened travel of a bent rod.

 

[OR VietVet]

I agree with @B-train. We both could be right but the compression is likely the key to the problem. I would still check what i mentioned, to remove all doubt.

 

[Alex_M]

All right, that's what I was afraid of. I'll definitely check the flex plate as you mentioned. Looks like I'll have a good core to build a stroker motor....

Thanks for the input gentlemen.

 

[OR VietVet]

All right, that's what I was afraid of. I'll definitely check the flex plate as you mentioned. Looks like I'll have a good core to build a stroker motor....

Thanks for the input gentlemen.

If I might interject here about a stroker motor. Unless you have a specific reason for a stroker, I would recommend a less expensive way to wake up a stock engine. Do a tune with Black Bear Performance. They are a vendor here and are listed on the Home/Forums page. You can customize the tune or do a "traditional tune" like I did. The engine acts normal till you ask more of it. Then it wakes up and turns in to fun. That tune, matched up with my Hellwig Performance front and rear sway bar kits, adds up to loads of fun and performance.
Like I said, mine is the traditional tune but you have other choices to go with. It does not cost anything to contact them and talk about possibilities.

 

[Alex_M]

Oh, I tune all my vehicles. Bought HPTuners years ago. The 6.0 will just get replaced with a reman 6.0 for now to get back on the road quick, but I'll keep the old motor for a core for a future project.

Thanks!

 

[Mudsport96]

Eh, hit the junkyard and grab one rod and piston combo and throw her back together. Did that with a 4.8 years ago because a guy i know drove through deep water and did basically the same thing. Truck ran for another 50k miles before he traded it in for a 2500 hd.

 

[Alex_M]

Already would have for any of our other vehicles, but this one I need to be back to 100% ASAP, and not have any doubt in it. This is my work truck that I rely on every day, only one in the fleet that gets "the royal treatment".

 

[Alex_M]

All right guys, been a few days but I finally got back to the truck. Got the motor out this morning and started pulling it apart. Flex plate is good. Confirmed bent rod, sitting about .075" lower in the bore than the other 7. Ignore the silicon around the intake ports - I know LS gaskets don't require it, it was a temporary measure. My gaskets were flat and I had forgotten I used my spare set on another vehicle.

Called around some machine shops yesterday to get a preliminary idea - see if the timeline would be feasible. The answer to that was no, but one at a reputable machine shop said, "but actually, I've got one sitting on the shelf. Guy was going to put it in his international scout, ended up getting divorced and didn't have the money for the bill. I told him don't worry about it, I'll find someone wants the motor. It's complete oil pan to intake. We went all the way thru it. Bored, decked, line bored, 3 angle valve job, new crank, balanced the rotating assembly, arp studs, the whole 9. Yours if you want it."

In short, I'll be picking that up tomorrow for less than what the reman short block costs.

Oh, and here's a shot of my "cherry picker". Y'all working without a level shop floor, here's the ticket.

 

[B-train]

Glad you figured it out. Love the shade tree engineering!!

Good score on the additional engine score

 

[OR VietVet]

Can't have too many engines laying around. I hope you get all the documentation for the claims of the work on that engine. If it isn't documented, it didn't happen....a lawyer told me once.

 

[Alex_M]

True there!

It's all documented, but there's no recourse - seller has not responded to any of my messages about being simply compensated for the bad injectors. This one will go down under "Lessons, Bought and Paid For" unfortunately.

 

[Alex_M]

Last update - she's in and running. Went ahead and did the TBSS intake with a 92mm throttle body while I had it apart again. Still some tuning to do, but I'm very happy.

Did have a heart attack moment when I first started it. Only read 25# of oil pressure. I had replaced the sending unit, broke the original getting the motor back in. Pulled the one off the Tahoe and stuck it in, showed 55psi. Whoo!

Motor is happy so far.

 

[rockola1971]

Great score on the engine! Sucks for the bent rod on the old engine....rebuildable core? Get nutz and bore it to a 5.7L LS1 then stick a hot cam in it and find a Esky with a blown engine! Hmmmmm...scouring the net now.

 

[Alex_M]

Yep, good core. Already a 6.0, so it'll become a 6.6l (408) stroker down the road.

 

[MassHoe04]

I love the engine hoist trailer rig! It has a giant drain pan built-in already!

You may be humble on what you have for shop and equipment set-up, but I'll tell you I am green with envy!!
A welder AND a roof overhead? My idea of heaven...

 

[Alex_M]

I tell you, both welder and roof are complete game changers. Especially the welder - well worth the $175 or so to get started. Pays back 100 times over.

The garage belongs to my folks. I do a lot of maintenance for them and get free use in return. Filled a giant hole that was left when I left doing full time mechanic work. Recently asked me about pouring concrete.... Said he'd buy the materials if I'd do the work. Time to brush up on concrete skills!