Colin Zwaschka

What pushrod length did you put back in? You used the LS7 lifters with the L8T cam, right? ETA: You also took 0.003 off the heads. Assuming stock head gasket thickness?

Yeah. Next up is cleaning surfaces. My least favorite part.

It's doable. Also nailed timing on first try.

I bought it from a used car dealer with a supposed bad motor. He thought is was a piston knock, but never had anything confirmed. He sold it at a price where if I had to put a new motor in, I'd still have a fair deal on it. I got it home and starting doing some diagnosing. I thought the sound was more pronounced on the passenger side, so I started with that valve covered. Turned it over for a bit and noticed the #8 exhaust lifter would stop working after turning over for a bit. I think the "knocking" noise was just the backpressure from the intake valve opening while the cylinder was still pressurized. I was hoping I could get away with just lifters and the delete (TSP plugs, Diablo tuner) since the L84 cams have the same lobe profiles for each cylinder, but after getting the heads off I stuck a camera down the lifter bores and saw that marring on the lobe. I should still be getting a good deal on the truck after this if I don't value my time too much. 20241011_182316.mp4

Schnikes. It worked. Thanks for the confidence. I probably owe you a beer or two fingers of Blantons. I did end up unbolting the oil pump and sliding it as far forward as I could. The oil pumps on the L84s have alignment dowels, so I'm not too concerned about getting it back in position. I just have to be careful with the rubber seal in the oil pan for the pickup tube. I was able to get enough slack that I actually just used my fingers to push the chain off the backside. I then had to fight trying to get the gear/phaser past the chain, but still a million times easier than dropping the axle or pulling the engine to drop the oil pan. Hopefully it goes back together. Now I just wait for my camshaft.

I like your suggestion of marking the flex plate at locker at TDC. That's a good check after reassembly (assuming I can find the sweet spot). I have a piece of fishing line tied around the top of the chain to try to keep it from dropping, and a zip tie off to the side to keep it from falling out of reach if the fishing line breaks. Did you unlock the flex plate to be able to rotate the cam gear when you were walking the chain off? If so, were you able to get the cam sprocket back in in the right spot on the first go? That seems like the easiest way to find the sweet spot, but it also seems like it would be more difficult to get things lined up right, but with the mark on the flex plate and lock, you'd at least know that you have to pull it off and adjust over a tooth or so.

Do you have a picture showing where the sweet spot is? I was trying right here so the phaser plate doesn't hit the oil pump, but I wasn't having much luck. I've got one gear tooth hitting on top of the driver's side chain guide. I'm going to try turning the engine one-half of a gear tooth further and see if that helps. Yes, I have the flex plate locked.

How? Did you walk the chain off the phaser gear?

I got my heads off last Friday and inspected the cam. The #8 exhaust lobe is marred, so I'm proceeding with a full cam swap, which adds a ton of work. On the L83s,s if you were real careful and crafty, you could remove the bolt from the oil pickup tube to remove the oil pump (necessary to remove timing chain) without removing the oil pan. The L84s don't have a bolt into the oil pickup tube, but the oil pump sits a good 1.5" lower than the top of the oil pan lip, so the pan has to be removed in order to remove the oil pump. Option 1 is to drop the front axle (remove spindles, struts, axle shafts, drop axle). Option 2 is to pull the motor. I've been chatting with a guy on Reddit doing the same thing. He has a lift and has dropped the axle. I don't have a lift and I'm going to try to pull the motor instead. While I have it out, I'll replace the rear main seal. Such fun. It has 130k on it, so new timing chain and tensioner, new oil pump... For those wanting to disable the system, you can honestly just unplug the solenoid wiring harness and the stock lifters will act like normal lifters, though you'll have to live with the MIL light being on until you unlock the ECM and disable the DFM/AFM. I have no idea if this improves the durability/life of the lifters, though.

My apologies for stirring up an old thread, but did you ever get this resolved? I'm in a similar boat with a collapsed #8 exhaust lift on a 2019 L84. Michigan Motorsports agrees in theory that a cam swap shouldn't be required, but they have not tested it. Texas Speed Performance hasn't tested it, either. Any insight would be greatly appreciated.

I'm still looking for answers myself. If it is the L84 with DFM, a cam swap may not be necessary because lobe profiles should be the same for all 8 cylinders (this was not the case for the L83s where the 4 AFM cylinders had a different profile from the non-AFM cylinders, which is why they need to be replaced when going to the LS7 style lifters). I called Texas Speed Performance to see if they had any insight, but they have not tested the DFM delete on the L84 while maintaining the stock cam. Here's a response I received from Michigan motorsports: "I agree that in theory, you shouldn't really need to replace the cam when doing a DFM delete on those newer L84 and L87 engines since all the cylinders would have the same lobes. We haven't personally tried it ourselves here though, so I can't say for sure if it is fine or not. We have asked some of our shop customers to try it as well, but so far they have all just been working on customer trucks that they can't risk having a come-back on so they have all been using the L8T camshaft on those L84 engines when doing the deletes to be safe." I'm hoping the OP has gained some insight on this and sees the activity on this thread and responds.

Rob, did you proceed with your DOD/DFM delete? I have a 2019 Silverado LTZ with 129,000 on it I just bought with a supposed bad motor, so priced accordingly. I pulled the valve cover and found that the #8 exhaust lifter is collapsed, so I'm planning to pull the heads and replace the lifters with non-DFM lifters. I'm trying to find a definitive answer to whether a cam swap is required, though. I know it was with L83-AFM engines, but the L84 has DFM on all cylinders, so I believe cam lobe profiles should be the same for all cylinders, so swapping the cam shouldn't be necessary. Thanks