Tune or Bad Injectors sticking valves? 408/4L80E

[CptMidway]

Hi all,

Having issues with either the engine builder or the tune

Engine Specs:
408 Stroker
243 heads - CNC'd
Decapped injectors - Benched to ~78lbs
234/242 .601/.605 112+2 Cam

Vehicle:2005 Silverado 2wd w/ 4L80E swap in it and Circle D 2600 Stall.

The engine has bent valves on 2 separate occasions. The first time was an Exhaust valve. The builder said the tune was bad as all 8 Ex valves were hot and that they got stuck in the guides. They weren't burnt but they were definitely hot. Second time it stuck an intake valve - Ex valve was getting there too. They're telling me that the valve was washed out from over fueling. First time it was all 8 Ex valves that were sticking. First time this happened I drove the truck maybe 10 miles. Second time I had at least have 30 miles on the truck around town.

Seems to drive fine part throttle around town. WOT seemed ok too. But both times the valves stuck wasn't necessarily during a WOT run, but it was in the timeframe of doing so.


Started off with a mail order tune and sent in the datalogs for feedback - reply was that they were all good. I don't have the log for the time the Intake valve stuck. I can try to get that one. So currently, the Builder is saying it's either the tune or the injectors.

I've included the logs and the tune. I apologize in advance for my ignorance on this, still stumbling though HP tuners and learning slowly with the Ed Mowton's/Throttle Up's Tuning Course. Was really sorry to hear he passed away.

Corrective actions considered are:

Replace decapped injectors with Factory LS3 injectors
Mill some 317 heads I have (to keep compression up) and put them on.
Start from scratch on a tune

Any insight on what might be causing the issue(s) would be appreciated!

CptMidway

[5FDP]

For sure get better injectors, decaps are nothing but trouble.

Fix your cylinder volume, the computer still thinks it's a 5.3 engine and all the airflow/fuel calculations are off because of that.

If injector data is good and the engine has no vacuum or exhaust leaks it makes fixing the MAF/VE much easier and faster. The majority of driveability problems can be fixed if the fueling is correct. Minor changes to timing and idle stuff happens easier if the fueling is correct.

[CptMidway]

Appreciate the input 5FDP.

When reviewing the tune from the mail order tuner I noticed that the displacement was off but after the feedback from the tuner that it looked good I went with it. Other than the bending valve issue, when I've driven the truck I didn't notice and driveability issues - which makes me question the claim of the tune being the issue.

I'll order replacement injectors to start. Any suggestions other than ls3 ones? Rockauto has Bosch ls3s for a pretty good price.

[kingtal0n]

bending a valve is a mechanical issue. If you've modified the head or block in any way that was prob a mistake and caused your issues.


The factory head and valve hardware (except springs) exactly as it is from the OEM with 150,000 miles can support 800rwhp or more with no issues.

So I suspect somebody messed your stuff up. In 20 years tuned 100+ cars and never heard of a tune causing mechanical engine damage like you describe.

Tell me exactly how its possible? Liquid fuel hits the closed intake valves in 100% OEM applications as it is, that is how they are tuned from the factory.

[CptMidway]

Heads were skimmed to clean the surface and rebuilt by the shop. Block wasn't decked to my knowledge. Builder doesn't have a build sheet to confirm the head information or the block info though.

The current argument from the builder is that a bad injector is flooding the cylinder/washing the valve with fuel causing this stuck valve. I looked back at my notes and this is the same cylinder that bent an exhaust valve the first go around. They've stated there was a bunch of fuel in the oil, but no apparent washing of the cylinders. They were going to send the injectors out to have them flow benched to see if they are the issue. Either way, they will be replaced.

I don't necessarily buy the intake valve excuse, but it is peculiar that it's the same cylinder as last time.

[blindsquirrel]

This is one of those situations that can only be figured out by someone who can lay their hands on the physical parts and take real actual measurements. Shopping it to different forums isn't going to get you anywhere but more frustrated.

[CptMidway]

Fair enough and you are right. Problem is I don't have the ability to put my hands on the data from the builds to verify anything which is very frustrating. Asking around to see if anyone has been in this situation before and what they've found is my end goal. I find it hard to believe that I'm the first one who's ever experienced this issue.

Appreciate the help and no bs responses everyone.

[kingtal0n]

If an injector is spraying too much fuel, the engine will misfire or run rich or both. You can see right away on the wideband something is wrong either way. You should have a wideband and be familiar with how it acts when an engine is running right and tuned well.

Fuel will wash the oil from cylinder walls which leads to wall wear, small doses will result with reduced compression over time (it can take 2 to 10 years to lose 20 to 30psi of cranking compression, we see this in 150,000 miles sr20det engines where the owner had installed a atmospheric bypass on factory style ECU with a MAF).
When the engine misfires from too much fuel, the fuel is wet liquid and it enters the exhaust where, if the exhaust is hot the fuel will quickly vaporize and explode causing a backfire. This is another sign of a leaking injector, e.g. cars decelerating with a constant pop ppop popping noise indicates a leaking injector.
Another sign is carbon coating, running rich or liquid fuel/too much fuel (its too wet with fuel, understand? if the injector is leaking) causes the plugs to show up wet, wet with fuel, and blackened, coated in soot from running rich on that one cylinder (if just one injector leaking), so this is part of diagnostics you should be looking at the plugs for signs of a leaking injector
Finally a large enough fuel liquid leak will cause hydrolock, stop the engine in its tracks and put a hole in the piston or bend the rod. Very noticeable.

I would think between the backfires, erratic wideband, misfires, plug discoloration, fuel smell, etc... it will be very easy to diagnose a leaking injector. Or very obvious that a cylinder is running rich enough to cause some kind of mechanical issue. That is quite a bit of fuel to have some profound affect on mechanical parts like that.

[dbright]

I think your pistons and valves are having an affair and you need a different engine builder. Having the engine apart twice in 40 miles is crazy. If its too rich the exhaust valves should be cooler than normal. Rings can get washed out, but not a valve. He's using tune as an excuse.

[kingtal0n]

Exactly. The factory injector spray is directly on to the intake valve where liquid fuel puddles and sits there when the engine is cold. All OEM engines do that, cold fuel puddles on the valve, the colder the valve the more liquid fuel will hang around. This is why its hard to start a cold engine on alcohol, the act of vaporizing alcohol is more endothermic than gasoline which further lowers the temperature of the already cold valve (it can form ice) and this prevents the rest of liquid fuel from vaporizing quickly so liquid fuel enters the cylinder and liquid fuel does not burn when exposed to flame, The fuel must reach a gas state to burn.

If the valve is fully warmed up, fuel vaporizes quickly and turns to a gas state where it can begin traveling up the intake port and into the plenum. There is some fuel saving benefit to setting an end of injection time closer to the intake valve opening point because it allows less time for vaporized fuel to escape intake ports after injection.

In any case, liquid fuel sits on all cold intake valves of all engines using typical MPFI EFI. They are unaffected by liquid puddle of fuel.

[Alvin]

I only checked one log but the fueling looked reasonably close.. no where near burning valves or anythign like that.

I'd have someone else fix the heads but I'd also get rid of those injectors. Who knows if one is occasionally sticking or something like that. I'm seeing enough stock injectors go bad in LSX vehicles older than 15 years that maybe that + decapped = big wild card.

[CptMidway]

If an injector is spraying too much fuel, the engine will misfire or run rich or both. You can see right away on the wideband something is wrong either way. You should have a wideband and be familiar with how it acts when an engine is running right and tuned well.

Fuel will wash the oil from cylinder walls which leads to wall wear, small doses will result with reduced compression over time (it can take 2 to 10 years to lose 20 to 30psi of cranking compression, we see this in 150,000 miles sr20det engines where the owner had installed a atmospheric bypass on factory style ECU with a MAF).
When the engine misfires from too much fuel, the fuel is wet liquid and it enters the exhaust where, if the exhaust is hot the fuel will quickly vaporize and explode causing a backfire. This is another sign of a leaking injector, e.g. cars decelerating with a constant pop ppop popping noise indicates a leaking injector.
Another sign is carbon coating, running rich or liquid fuel/too much fuel (its too wet with fuel, understand? if the injector is leaking) causes the plugs to show up wet, wet with fuel, and blackened, coated in soot from running rich on that one cylinder (if just one injector leaking), so this is part of diagnostics you should be looking at the plugs for signs of a leaking injector
Finally a large enough fuel liquid leak will cause hydrolock, stop the engine in its tracks and put a hole in the piston or bend the rod. Very noticeable.

I would think between the backfires, erratic wideband, misfires, plug discoloration, fuel smell, etc... it will be very easy to diagnose a leaking injector. Or very obvious that a cylinder is running rich enough to cause some kind of mechanical issue. That is quite a bit of fuel to have some profound affect on mechanical parts like that.

Thanks for the info, all the info you posted points to the decapped injectors being the likely culprit - as everyone here has already said. The plan is to still have them sent to be flow tested to confirm. I didn't notice any popping on the exhaust or drivability issues you would assume from an issue like this. The #4 cylinder did have carbon coating on the head. Plugs from the front 4 looked like they might be carbon coated - they weren't oily.

I have a set of Bosch LS3 injectors on their way with the adapters needed to work with the truck intake.

[chrisxiv]

If an injector is spraying too much fuel, the engine will misfire or run rich or both. You can see right away on the wideband something is wrong either way. You should have a wideband and be familiar with how it acts when an engine is running right and tuned well.

Fuel will wash the oil from cylinder walls which leads to wall wear, small doses will result with reduced compression over time (it can take 2 to 10 years to lose 20 to 30psi of cranking compression, we see this in 150,000 miles sr20det engines where the owner had installed a atmospheric bypass on factory style ECU with a MAF).
When the engine misfires from too much fuel, the fuel is wet liquid and it enters the exhaust where, if the exhaust is hot the fuel will quickly vaporize and explode causing a backfire. This is another sign of a leaking injector, e.g. cars decelerating with a constant pop ppop popping noise indicates a leaking injector.
Another sign is carbon coating, running rich or liquid fuel/too much fuel (its too wet with fuel, understand? if the injector is leaking) causes the plugs to show up wet, wet with fuel, and blackened, coated in soot from running rich on that one cylinder (if just one injector leaking), so this is part of diagnostics you should be looking at the plugs for signs of a leaking injector
Finally a large enough fuel liquid leak will cause hydrolock, stop the engine in its tracks and put a hole in the piston or bend the rod. Very noticeable.

I would think between the backfires, erratic wideband, misfires, plug discoloration, fuel smell, etc... it will be very easy to diagnose a leaking injector. Or very obvious that a cylinder is running rich enough to cause some kind of mechanical issue. That is quite a bit of fuel to have some profound affect on mechanical parts like that.

very well explained. I completely agree. If I were to add another symptom into the leaking injector(s) issue I would add that it can quickly start to eat away or deteriorate the cats as well, if the problem is not cured.