5.7L 3UR Broken Lifter/Lash Adjuster

Joined
Jun 5, 2019
Messages
20
Location
Abu Dhabi
I own a Twin Turbo '07 Regular Cab Tundra built by Dynosty. It currently holds the world record in the 1/4 mile @ 10.5. By the end of last season we found a few sensor calibration issues and the truck had a bit more in it but the weather was getting warmer and I thought I'd wait until next season.

Around March is when I took it to a roll racing event and noticed it was a bit down on power. I was barely able to beat a BMW 750 on the street on low boost as well. It felt like I was losing one cylinder and looking at the logs, bank 2 was going lean up top and I was 1 psi short of my boost control target. Revving without load same thing happened around the same RPM with a very faint vibration, so I thought maybe it was the valve springs giving out. Before that I went through the check list (plugs, coils, injectors, etc.) nothing worked. All cylinders were healthy at around 185 psi on a compression test too.

It had two seasons worth of racing @ 25 psi on E85, daily driven @ 14-17 psi on pump gas and revs all the way to 6800 RPM (It has stiffer valve springs). So it was time to check the valve train. I initially thought it would be VVTi/spring related, but we found one of the intake rockers/followers on cylinder 4 fell off and the lifter/lash adjuster broken. I remembered then that I could hear a faint pebble sound coming from the engine but never thought much about it. It was probably the rocker/lifter tip kicking around under the valve cover. Luckily, nothing seems to be hurt and the head looks basically brand new.

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With all new lifters, tensioners and replacing the one rocker, all is back to normal. I talked to a friend who works on the 3UR regularly and he said he only saw this happen once on a completely stock engine a few years ago. So I'm hoping it's just a single weak unit seeing as how the other 31 rockers and lifters looked brand new.

My only concern is I don't even know how that could happen in the first place. My assumption is the rocker simply fell off and the lash adjuster shot up, hit the camshaft (which was unaffected btw) and broke.

Or it could possibly be the other way around where the lifter broke for some reason and the rocker fell afterwards. Which would explain why the cam was unaffected.

If anyone faced a similar issue where a lifter broke, please share your experience on why or how it could happen. I would like to avoid this happening again as the rest of the truck seems to be fine otherwise with all the abuse.
 
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