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Gen III 5.3 swap valley cover and sensor questions
Hey everyone, this winter I will begin the process of swapping in a freshly-rebuilt Gen III 5.3 LM7 into my twin turbo '05 GTO. I'll be swapping over the needed parts from my LS2 (intake manifold, timing cover, sensors, crank pulley, accessories, etc.) onto the 5.3, but upon taking apart my LS2 engine I noticed that the valley of the engine block is different between both engines. I didn't get a valley cover with the 5.3 when I bought it, and it's obvious that the LS2 valley cover is not going to work with the 5.3.
Is there a particular valley cover that I should use for this 5.3 swap, other than the factory valve cover? Is there any reason I should use an LS1/LS6 valley cover instead? Also, what are the holes that I've circled in red in the picture below? Do I need anything in addition to the valley cover and gaskets for these holes, or do I need to plug them with something?
Also, I've heard that the LS2 and Gen III 5.3 engines and a different number of knock sensors. Any ideas on what I need to do to remedy this for the swap? Thanks a bunch!
The LS2 knock sensors are found on the side of the block. The Gen III knock sensors are found in the valley of the block, which is what those holes are for. The knock sensors themselves are different: Gen III are single-wire and Gen IV are two-wire.
You want to find an LS6 valley cover for the motor, such as one off a 2004 GTO. As for the knock sensor location, your harness has the plugs located on the sides of the block. I think your only recourse is to drill and tap the side of the block, or find something like this: http://www.ebay.com/itm/10mm-to-8mm-Step-Stud-M10x1-5-M8x1-25-31mm-OAL-Per-Piece-Ships-Fast-/161052537435?pt=Motors_Car_Truck_Parts_Accessories&hash=item257f7ab25b&vxp=mtr#ht_520wt_867 and use it on one of the holes already drilled for your stock knock sensors.
Thanks so much, great information you just provided! That's all starting to make some sense. I'd hate to have to drag that heavy 5.3 to a machine shop to have it drilled for the knock sensors, but if that's ultimately the best way to handle this then that's just what I'll do.
I like your idea of using an adapter stud so I can utilize my LS2 knock sensors in place of the 5.3 knock sensors, but due to the different shape/design of the LS2 sensors It doesn't seem like that will work unless I use a long threaded coupler or something an raise them out beyond the height of the valley cover enough for the the connectors to clear.
I'm wondering if there isn't just some simple wiring to do to use the 5.3 knock sensors with the LS2 harness. Maybe just ground the ground terminal of the LS2 knock sensor connector to the valley cover, and then run the other wire directly to the knock sensor? I'm obviously not sure of the reason for the 2-wire LS2 sensor vs the 1-wire 5.3 sensor... any ideas on that? I can't seem to find anything on that either. Thanks again man!!
I spoke with Eric at CSP last night, and he had a great suggestion. What he did for his 5.3 swap in his LS2 GTO was he inserted a heli-coil into the extra engine mount bolt hole on each side of the block. He used the heli-coil as an adapter, so he could insert the LS2 knock sensors into the side of the 5.3 block. I didn't ask him, but due to the length of the wiring to the knock sensor connectors on the LS2 wiring harness, you probably don't even have to splice into the current wiring to lengthen it or anything. I'm definitely going to aim for his method, and hopefully have the car over to CSP very early next year to put some #'s down.
Sorry, my misunderstanding! I thought you were suggesting using the LS2 knock sensors in the stock location of the 5.3 somehow with these adapters. Now I see what you meant, and like your idea of using those adapter studs versus heli-coils. Great suggestion, now that I understand it.... going to do exactly that
10-14-2014, 11:48 AM
Gen III 5.3 swap valley cover and sensor questions 
