Figured I'd come back and update this thread with my findings for anyone else that happens to be in this predicament.
I ended up tearing back into the truck and found that my brand new SoCal Diesel injector hold down on cylinder 7 had snapped clean in half.
The injector had lifted and was allowing combustion gas into the valve cover area and from there it was going down to the crank and out the oil fill tube and PCV pipe making it look very similar to cylinder blow-by.
Reached out to the vendor from this forum that I've been using and SoCal's fix was to send me a replacement for the one broken hold down.
Replaced the snapped hold down and on my next start-up the same thing happened all over again, but this time on cylinder 2. Starts up fine, then it starts making a tapping noise, and then the smoke starts. When I compression test the cylinder it ends up being low but not dead.
We reached out to SoCal again and this time they sent an entire new set of hold downs.
I tore into the driver's side and replaced the entire bank with the new set, in the process also finding that the #6 hold down had also snapped but was still being held by the nut.
I compression-tested the entire engine again and all cylinders were 400-410. Including those with the 3 remaining hold downs from the first batch on the passenger side.
I figured I'd give the engine a crank before tearing back into the passenger side to replace the remaining, just to see if it would run fine with the 5/8 I had replaced. Sure enough, nope. Ran fine, then tapping, then smoke. Cylinder #3 was down to 250 lbs.
At that point, whatever, I was gonna replace those anyway, so I tore back into the passenger side and replaced that entire bank with the new set.
Here's the really frustrating part.... I compression tested before start last night. Once again, all cylinders were at 400-410... cranked it, started it.... and the same thing is happening all over again. Tapping noise, then smoke, and now cylinders 7 has 300 lbs and cylinder 6 has 210 lbs.
I am to my wit's end with these damn hold downs right now. I started thinking that maybe my torque wrench was off and was over torquing, so I tested all three of my torque wrenches against each other and all came to the same reading, including a Snap-On wrench, and two digitals. Three torque wrenches cant be wrong to the same exact reading.
So here I am...2 and a half times into an injector job on an LB7 due to faulty injector hold downs, and with a third time still to go.
Currently I'm waiting to hear back from my vendor on what's gonna happen from here. At this point, I just want SoCal to give me my money back so I can go get a billet hold down set from Industrial Injection and be done with this.
Picture is from batch 1's # 7, 2, 6, and 3.
Probably gonna work on tearing down again this weekend and I'll update if I'm wrong about the new batch, but with identical symptoms and sequence of events I highly doubt it.
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