Engine Tick leading to Exhaust Valve Tip Failure at 190K.

[Jedibusiness]

Long Story. 

 

1980 and a few months before standing on yellow footprints, in high school auto shop class, Mr. Collins saw I was having difficulty mating a transmission to an engine.  Called me out from under the wagon, reached into his pocket and pulled out 30 cents and told me to get a soda.  Mr. C was a quiet man and often taught us without saying a word.  I complied, bought a soda added Cheetos, walked to the back over-viewing the canal.  Finished, crawled back under the problem and withing 30 seconds the bits magically lined up and I moved on with the build.  He knew I needed a break before I did.  Fast forward eight years, snapping in a new crew maintaining F-18's, one of my Marines having difficulty installing a fuel pump on a gearbox, so I reached into my pocket pulled 50 cents and told him to get a soda, he stared at the coins, looked bewildered, however me being senior complied.  Coming back from the break, told him how to position his body and what Zen like hand force would pop it into place without buggering the o-ring.  When you can, pass what you learn to the replacements.

 

Late 2015, returning from my cave analysis of gas vs diesel chose the 6.0 2500HD for my business installing pack lines in processing plants.  Using a Truck Camper and 20 foot equipment trailer, I stay on-site till the job and training is done.  This means 98% of this trucks' life is at payload, pulling 10k pounds, making money every time I get in it.  Current mileage 190,090.

 

Until 185K my rig serve faithfully, except for a craced brake line connection near the differential at 114K miles in Michigan.  Did a combat repair late Saturday afternoon before the town shut down and every auto parts store didn't have the firing solution...which came from all places, a muffler shop...then drove to KY for a Monday meeting to close on another pack line...but that's another story.

 

Starting hearing a tick on start up, but after warm up it would go away.  Inspected exhaust manifolds and noted driver side rear bolt head was gone, carbon was on the head and needing the truck for work, opted for the Kral manifold clamp.  Drove another 5K on the the truck, but no luck stopping the tick...knew the easy way was over and next step was pulling the exhaust manifold.  Also starting getting a intermittent P0306 and P0303.

 

Removed the exhaust manifold and the warp was troubling, but I foolishly tried to file out the warp and replaced manifold gasket then reinstalled.   Still ticking, the last gasp was a motor flush hoping something would magically free a lifter and all would be well.  Nope, still had the tick and getting louder, knew after 39 years of not seeing the inside of a V8 valve cover, what I had to do.

 

Now for young folks, removing valve covers may not seem a big deal, but 39 years ago vehicle maintenance didn't include ECM's, rocker rails, hydraulic roller lifters, fuel injection on cheap cars, OB code readers,  variable cams /sensors, or electronic ignition.  If one said, some day in the future each cylinder will have its own coil pack, that would be grounds for throwing you out of the shop. 

 

Pulled the valve cover, still no clue then proceeded the rocker rail.  There it was...source of the tick...missing valve tip.  Still had some key metal so maybe I could have gone another 2K miles but sometimes you get lucky and save a motor.

 

Down that far, opted to pull both heads, replace exhaust valves springs, seals, lifters and buckets.  Cam was good. 

 

Cleaned carbon off the pistons using Gunk Motor Flush and removed rubber stuff remaining on the block.  On the advice of my head re-builder, replaced gaskets with AC Delco OEM.

 

Reassembled the heads.  Note rocker replacement.  Purchased from Summit and had to sign a waver stating it was a performance part and must be used off road.  Although its a GM part number and not aftermarket, played the click here game and received them without enviro-police showing at my door. 

 

Since the block remained in the truck, opted for ARP bolts so I didn't have to mess with angle torque near the firewall.  Have to say at my age, 89 foot pounds laying horizontally, in the Superman position over the grill just about kicked my ass.  Torquing clam-shell jet motor mounts was a lot easier.

 

Less I forget...if your going to tackle this job...get the thread chaser.  This was residue after cleaning with brake cleaner and blowing air into the threads

 

 

Driver side Exhaust Manifold (Dorman) from NAPA went on without issues, however the passenger side (ATP) from Rock Auto was a bust.  Removed from plastic, lined up to the head and missing #6 exhaust flange.  Air bubble in the cast.  Shipped back to Rock Auto, they refunded my coin. 

 

Pulling off the passenger manifold heat shield and showed a nice 3 inch crack. Most likely the reason for the P0306.  But to be safe, replaced the coil and fuel injector.

 

Off to NAPA for a manifold (Dorman) but again another problem.  Manifold made in China, doughnut seal made in India, parts assembled in Mexico...what could go wrong?  Exhaust doughnut was too small.  Back to NAPA dragging the old manifold, explained problem to two hard charging ladies who knew parts.  They sourced the right doughnut (Fel-Pro 61694 2007-12 - replacing 20987829).  Next time I'm opting for stainless headers.

 

Final PITA issue was brand new AC Delco 7mm PERFORMANCE wires missing a spark plug clip.  Clue to the problem was written on the box.  Assembled in Mexico.  There's no quality control when your paying $3 and hour.  Oh...back in my day Valve Covers were made in the US, now its Mexico.  Explains overpriced trucks and the bi-annual 20% discount on new trucks.

 

Refilled engine oil, noted dip stick was missing, reinstalled,  bled the fuel rail and the 6.0 fired right up.  Two hesitations clearing remaining air, warmed up and settle into a good smooth idle.  Then heard a usual sound, not quite a tick or a tap so I shut it down.  Checked the dip stick and the level was higher than normal, then realized I put 4 additional quarts into the motor.  Pulled the drain plug and was horrified seeing a milky tan streaming into the oil pan.  Oh crap leaking radiator fluid in the block, really thought I mucked up the head gaskets.  Then smelled the oil and noted that kerosene motor flush and realized it oozed past the rings while cleaning carbon off the pistons.  Two oil changes later, all is well and idles smooth.  Did a forty mile loop, no leaks, radiator level steady, and oil clear.  All bolts and parts accounted for except one nut.  Most likely goes on the intake manifold but not worrying about it.

 

After 39 years, I can still tally up details of a top end rebuild while working my way around a small block.  I can say what we dreamed about in performance parts producing higher horsepower and torque back then, is common today.  Spark plugs lasting 100K miles (mine went 130k).  Rear oil seals intact, MAF sensors, billion cycle fuel injectors, plastic intake manifold, variable cam geometry, 185K on an engine working hard without failure and requiring only regular maintenance.  These are great days and bless Chevy for continuing to upgrade its small block giving power to people making coin using their engineering.  Also thank the internet. Anytime I had a concern or wanted more information, this site, LS1.com, Youtube was available along with ordering parts that kept overall cost below $1300.  A lot lower than a diesel rebuild, but then again most likely wouldn't have lost a valve tip.

 

 

 

 

 

 

 

 

[davester]

Nice pics and writeup.

[GTBensley]

Sounds like you got pretty good life out of that motor before it needed work and ultimately didnt require that much work to fix it. 

 

Any idea what caused the failure? 

[Jedibusiness]

You’re correct.  I put 9.5 years on a 3 year old truck at either full payload, tow or both.  

 

We know the cause was a exhaust valve tip separation from the valve.  Speculation is driver side head showed more varnish than the passenger side suggesting more heat.  However this is normal.  The amount of carbon on pistons and exhaust valve was excessive.  Exhaust manifold warp on driver side and 3 inch crack on passenger side is another heat indicator.  Rebuild shop reported passenger exhaust valve seats had some pits and could explain intermittent cylinder 6 misfire and blow-by heat as cause for the cracked exhaust manifold.   Number 3 cylinder also showed oil leaking past the exhaust valve seal. 

 

My take is the oil change intervals directed by the truck monitor averaging 7-7.5k miles under my driving conditions, is perhaps too long.  The head rebuilder suggested no more that 4-5k synthetic and 3000 miles for conventional or blended oil.  Also I fuel at Pilot and Flying J and octane rating fluctuate between 85 and 87.  

 

I’ve alway poo’ed fuel boosters or cleaners but will incorporate them into my maintenance schedule.  Since my motor is flex fuel and travel the midwest, every other fill up should be with E-85.  My engine shop reports no carbon build up using it. 

 

As stated my truck has served me well.  Fact is no gas motor used in full time HD conditions will be 100% reliable over 150k miles and why fleets usually sell them at 100k.  The pearl here is if you follow the maintenance schedule and budget a top end rebuild around 175k, (assuming using your labor) Chevy’s L96 is a competent performer.    Some will remark I should have sold the truck, bought new and renewed the section 179.  Problem is my 5 years is not up and would incur a tax penalty.  Others would suggest moving over to diesel but the cost per mile, regeneration and emissions negate any advantages. The exception being perhaps I would not have lost a valve tip and farther tank range could be a tipping point.  Contrast that with the ease of repairing small block over diesel and I’ll stay with the gasser. 

 

Finally, I drive rpm more than speed limit.  Staying below 2000 rpms on the flats gives me the best mileage. On climbs, rarely go over 4800 rpm and usually pull between 3300 and 4000 rpms.  

[GTBensley]

Seems well worth the cost of fixing it, that is a very small amount compared to the cost of a replacement truck. 

 

I would bet you would have spent more by that mileage in a diesel with repairs....just a guess though.

 

You are probably spot on with your theory of longer oil changes causing the problem while working the motor harder then most. I go off my monitor but change when I hit 40-30% life left and also dont use my truck as hard. 

 

 

[Jedibusiness]

Parts and head work under $1500. (Includes troubleshooting before head removal).  Cost per mile. 0.000005263157895.  

 

Now have 800 miles on the rebuild.  Motor response like new and getting 16.8 mpg at 60- 62 mph @1750 rpm -Unloaded. 9.5 mpg with 4K pound truck camper with crosswind.