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  1. R

    Truck smells like farts in the morning

    A rotten egg smell is usually an 02 sensor sending a false lean signal to the PCM, it tries to correct it by adding too much fuel. If you disconnect one of the primary 02 sensors and the smell goes away on cold startup then you found the failing sensor; it will turn on the MIL light but it...
  2. R

    DOD Delete Theory

    Finally got it fired up around 8pm last night, unbelievable how much longer it takes to reassemble in this Envoy chassis compared to the Yukon; this strut style front suspension may be nice to drive but the towers are miserable to deal with for maintenance. Engine runs great, very quiet and...
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    DOD Delete Theory

    Did the compression test today with encouraging results, test was done with all new lifters that have never ran, no exhaust or intake manifolds installed and no plugs in any cylinder. As I mentioned before all lifter preloads have been verified to be in spec for LS7 lifters. On the driver side...
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    DOD Delete Theory

    Okay, another update; I keep getting sidetracked so this is taking longer than I thought. I installed the new LS7 lifters, trays and got the heads back on so I was able to check the pushrod length to see if my theory was valid; I appear to be wrong. This DOD engine uses the same pushrod in...
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    DOD Delete Theory

    I have a partial update, didn't get as much time on the engine as I wanted this weekend but I did get the heads off & lifters out. It was what I was expecting, the only lifter that was stuck was the #1 intake DOD lifter, all 16 lifters had no damage on any of the rollers and the cam lobes all...
  6. R

    DOD Delete Theory

    There is a couple good YouTube videos that disassemble the DOD lifters and show what happens when they fail to reseat in the V8 mode, interesting theory but also becomes obvious why they are such a trouble spot
  7. R

    DOD Delete Theory

    The factory setup is all 16 pushrods are the same 7.397 inches according to GM.
  8. R

    DOD Delete Theory

    That link from LS1tech is one of the threads I read when I got this idea, lots of guys have tried using the DOD cam but I haven't read of anyone trying to use the DOD cam and correct the geometry with pushrod length; I am going to be the Guinea Pig I suppose
  9. R

    DOD Delete Theory

    I think the loss of compression is a lot more than 15 psi on the DOD cylinders if you just swap out the lifters, I was hearing 55 to 60 psi cranking compression from a couple guys who tried it but I wasn't there so I can't verify that; but I doubt 15 psi below normal would register a misfire...
  10. R

    Proper DoD delete oil pump

    The engine I am hoping to pull apart for a delete this weekend has the worse coking in the cylinders I have ever seen in my bore scope but all of the plugs look great, GM coil packs are awesome.
  11. R

    DOD Delete Theory

    Well, literally every company that sells the parts says the cam must be changed, that's likely why there is skepticism; I just can't think of a reason why it won't work and this is a rig I bought real cheap just for the engine so I thought I would try it just to test the theory. Nothing to...
  12. R

    Proper DoD delete oil pump

    Put a bore scope in the AFM cylinders and the non AFM cylinders and you will see the difference, insufficient PCV oil mist can cause this as well (why catch cans became a thing) but a catch can will cure that issue with the PCV entirely; the DOD system will coke up either way. And that oil psi...
  13. R

    DOD Delete Theory

    There is no way to compensate in the tune, the lobes lift, duration and separation angle must be the same on all the cylinders in V8 mode; the difference is the smaller base circle before the lifter starts up the lobe. The longer DOD lifter makes up for this loss in distance so all of the...
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    Proper DoD delete oil pump

    By leaving both valves closed under cylinder deactivation the disabled cylinders have trapped air which cushions the pistons and helps the engine feel smooth when in 4 cylinder mode. The engine is designed to lubricate the cylinder from beneath and control the oil to a limited amount via the...
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    DOD Delete Theory

    They do offer a kit to do it, most DOD delete kits don't include a cam, just the option to add the cam you want; most kits also specify to verify the pushrod length needed after the heads are back on and order the appropriate lenth, don't just assume the stock pushrods will be right. People skip...
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    DOD Delete Theory

    This makes no sense, the length required is what is necessary to preload the hydraulic lifter to between 50 & 65 percent of its plunger travel to establish normal operation of the valves; which area in that straight line or which component has which individual length is irrelevant as long as the...
  17. R

    Any good resources on how to install an oil catch can?

    It goes inline between the pcv on the drivers side valve cover and the intake manifold port; no changes to the passenger side connection.
  18. R

    Proper DoD delete oil pump

    Exactly, I have never seen a compelling reason to remove the factory DOD pump; it is the best factory pump ever put in the LS series engines. In fact the TSB from GM on the pan pressure relief valve is just as ridiculous, the DOD engines use oil because of the V4 mode; it has nothing to do with...
  19. R

    DOD Delete Theory

    I ordered everything but the pushrods from Summit today, when I figure out what length to order the 8 new pushrods I will post it as well as the results of this experiment
  20. R

    DOD Delete Theory

    I won't know for certain until I do it but when a dod engine is in 8 cylinder mode I don't see how the lobe specs can differ without causing a cylinder imbalance; that is why I think the only difference is the smaller base circle to account for the extra lifter length. If that length is...
  21. R

    DOD Delete Theory

    That's what I was thinking, the lift, duration and LSA pretty much has to be the same as the non DOD lobes for the engine to run correctly; so I think they just started with a reduced base circle so all the pushrods could be the same length. Like you say it's no big deal to swap the cam later if...
  22. R

    DOD Delete Theory

    I will obviously replace the cam if there is any damage, but I seriously doubt it given the intermittent nature of the symptoms and how well it runs and sounds when the lifter seats correctly. I am not trying to save money, I usually do this with a new aftermarket cam that improves torque and...
  23. R

    DOD Delete Theory

    I have a theory that I think I am going to try, looking to bounce it off of our mechanic minded members. 2006 Envoy Denali 5.3 Low miles (98k), cylinder 1 intermittent ticking, throws misfire code when ticking. I have disabled the DOD/AFM in the PCM and now need to address the hardware, all...
  24. R

    Any tips on bug and road tar/gunk remover?

    I use diesel fuel on a rag, never had an issue with paint damage
  25. R

    2012 Tahoe 5.3 tap/misfire

    It sounds like a faiiling/sticking AFM/DOD lifter on the number one cylinder, the tap goes away when the plunger manages to snap past the dogs but it is not fully extended so it misses slightly at idle; once the RPM is increased the miss is pronounced enough for the computer to narrow down the...

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