2018 L83 DoD Delete = Running great, then no Compression

[Kubs]

I just got done doing the DoD delete on my '18 L83 Silverado.  I replaced the cam with a BTR L86 cam (very mild) new lifters, lifter trays, dod delete plugs, all new VVT gears, chain, tensioner, oil pump etc.  I also added a 6.2L intake manifold and TB during reassembly.

 

The dots on the cam gear and crank lined up perfect, and engine spun by hand no problem on reassembly.  Once back together I held the throttle down and cranked to build oil pressure before starting.  Foot off the throttle it fired right up as soon as I hit the key. Idled beautiful without a miss, hesitation, lifter tick (reason for the tear down in the first place) or any odd noises.  After a few minutes of idling while I was checking for leaks and listening, the truck just shut off.  No bangs, rattles, smoke, nothing.  Just stopped like someone turned the key off.  Now when I crank the engine spins like it has no compression.  Very free.  No codes or check engine light either.

 

Feeling defeated I called it night cause it was like 10pm and decided to tackle it again today.  Im going to pull some plugs and check compression, and also pull a rocker cover to inspect, but what would cause it to lose compression all of a sudden?  How could it start and run great, and then not have anything?  Im at a total loss really.  Anyone else experience this?

Edited March 4, 2025 by Kubs

[rlcole321]

I did the same thing, your push rods are too long, once the oil pressure built up, it keeps the valves open, on my 2018 L83, it never had compression, had too measure the push rods I needed (with an adjustable pushrod tool) and get shorter ones. Hope you have a HPTuner, you'll need to "Retune"!

[Kubs]

So pushrods wasnt the issue.  Rotated the engine to where cyl 1 had both intake and exhaust valves closed.  Then I thought if I loosen a rocker I should see the spring move a little.  Nothing.  They are closed.

 

I got it the rest of the way apart over the weekend. The cam bolt backed out and the gear spun on the cam a little making it out of time and lacking compression. It also destroyed the pin to the point I cant get it out so Im out $400 for a brand new cam also...

A little background. I took the engine apart to replace the VVT after a P0016 code. I did a new cam gear/phaser, new bolt, tensioner, etc at that time. When I got it back together it developed a lifter tick right off the bat. I suspect it had been going out for a while and sitting with no pressure in it finally did it in.

I then took it apart again to do the DoD delete with LS7 lifters, new trays, cam, valve springs and seals. I reused the cam gear and bolt that had 2min of run time. GM says if you re-use the cam bolt the new torque spec is 47ft/lbs + 50° instead of +90°. I dont think this is tight enough apparently.

New cam, gear and bolt on order, and hopefully this is the last time I put this engine together. 

Edited March 11, 2025 by Kubs

[UrbanRage]

Damn, that sucks you're out $400, but at least you know what the problem was. Hopefully, everything will go smoothly with the installation of the new cam.

[Kubs]

Reviving this.  I had to step away for multiple reasons.

 

I had the heads re-done with new valves as when the cam jumped time it bent all the intake valves.  Its back together and starts and runs, but will idle rough.  Along with the new cam I also changed to the L86 intake and TB.  It might just need a tune now.  I cant datalog though because I am relying on the AFM disabler in the OBD port to allow me to test fire until I can get it to the tuner.

[mikeyk101]

Not sure if this will help but you can get splitter cables for the OBDII port to allow 2 devices to be connected. I have done this with a Range Disabler and an OBDII reader to monitor various engine functions. It has worked out very well. Not necessarily recommending this one but if you search on Amazon, there are many to choose from.

 

https://a.co/d/aLK2tUV

 

 

 

 

Edited July 21, 2025 by mikeyk101

[Kubs]

Truck is currently at the tuner.  The rough idle was a dead driver side O2, but we are now getting fuel trims about 15% different side to side.  Pass side is taking a lot of fuel out and cyl 4 spark plug was BLACK.  I think I have a hung up injector.  Hopefully that clears it up and I can finally drive this again.

[Kubs]

Closing the loop on this, replacing the injector allowed the truck to run well and be tuned.  It made 304hp and 333ftlbs on the rollers, with a 33" tall A/T tire and 93 octane.  Unfortunately I dont have a comparison to before all the work but it feels pretty healthy.  Very close to some 6.2L trucks I have driven.