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So now instead of a tubular seat brace that bolts to the thin sheet metal floor, then the side brackets and/or slider bolt to that... Ryan has made this 3D structure of plate steel reinforcements that is
similar in layout to the OEM stamped bits - but lower and thicker. The OMP side brackets now bolt to this reinforced structure, which is welded to the non-flat floor along the bottom seam. This new structure now takes up for the funky floor shape, is lower than the OEM reinforcements could allow, and much more rigid and strong than what we had in version 2.
HYBRID ACCESSORY DRIVE + DRY SUMP PUMP
We normally use the 1998-2002 Camaro LS1 front drive accessories on both our E36 and E46 LS swap kit installs, as these offer the most compact layout of power steering pump, alternator, and water pump without fouling the frame rails or inner fenders. These 4th gen drives do push the pulleys forward in the engine bay more than the Corvette C5/C6 drives, but less than the LS truck drives. For this build we knew we needed a dry sump pump and we wanted to roll the radiator, which could put the bottom of the radiator close to the engine. To make room forward we looked at the C5 and C6 accessory drives for this build, but the traditionally high mounted Corvette alternator would need to move. Plus the power steering pump would need to be deleted.
http://www.nookandtranny.com/Info_LS...ontDriveConfig
The above link from Nook and Tranny is a great resource for LS drive layouts.
You can see the factory C6 Corvette Z06's LS7 engine accessory drive setup above at left and the LS2 CTS-V drives at right. Note the very HIGH and WIDE mounted alternator, common on the C5/C6 Corvette setups. Plus the power steering pump placement for the C6 - which we don't need due to the electric EPAS steering we have added.
For this M3's accessory drive setup we used a hybrid assortment of parts: the water pump and upper tensioner/idler from a 2010-13 Corvette C6 LS7 and the low mounted alternator and idler pulleys from a CTS-V LS2. Ryan machined a custom spacer, used a threaded hole on the CTS-V alternator bracket, and added a second "smooth" idler pulley near the alternator - the lower one shown in the picture, above right. The Pontiac G8 alternator bracket we used on some other Ls swaps sits in a
similar spot
but uses different brackets. This second idler helps give enough "belt wrap" around the main balancer pulley for the unusual "power steering delete" belt routing.
We chose the later LS7 water pump, which moves the water neck closer to the driver's side - making a shorter hose run to the radiator. Since we had never done this custom accessory drive layout before, once the final engine was here (with the balancer installed by HPR) a bit of measuring and a couple of belts were tested before the final serpentine belt length was nailed down.
While the HPR shortblock was awaiting the CNC cylinder heads, we borrowed the ARE 4 stage dry sump pump temporarily - to make sure we had no interference with the accessory drive bits we planned to use. The dry sump pump fits in the spot where the A/C compressor mounts - low and to the passenger side of the engine.
So this hybrid accessory drive setup gives us the best of both worlds: a low mounted alternator (CTS-V) along with a short drive setup front to back (Corvette). This added room up front with this drive setup will come in handy when we mount the radiator (below). This also opened up the top of the engine bay, near where we will duct the hood later.
CUSTOM LONG TUBE HEADERS
For an engine this big something larger than our production E46 LS Swap 1-3/4" primary long tube headers were part of the plan. We couldn't wait for the finished HPR 7.7L long block to arrive to begin the custom 1-7/8" primary header fabrication, so a mock-up engine and new accessory drive were installed for the early fab stages.
We were using bends, flanges, and collectors from a new supplier, and there were some... "issues outside of our control" that slowed delivery of the additional parts we needed to finish these for a few frustrating months.
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