SL-C Engine

If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower.
— Mark Donohue

The SL-C deserves a special engine. I spent time investigating Ferrari, Lamborghini and Audi A8 V10 engines. In the end I choose American iron (well, aluminum actually)... a supercharged LS7 built by esteemed engine guru Brian Thompson.

The belt shown above is a Gates K080653; 8 ribs, top width 1.087", outside circumference 65.922". They have a belt chart here. I have no documented ATI part numbers and according to ATI I would have to disassemble everything to gain access to their part numbers That #@(@!&! drives me nuts. After some back in forth with ATI they're pretty sure that I have a 916033A hub, with a standard Chevy big block 3.2" bolt circle and recess with a 2.050" ID.

This configuration has three problems: there is no provision for an alternator or an A/C compressor, the belt starts to slip a little before 900 HP and I’m going to replace the mechanical water pump with an electrical one. The plan is create three separate planes in front of the engine to drive the accessories:

  • Plane 1: Oil pump running on a cog belt and AN cooling lines

  • Plane 2: Damper and supercharger running on l be a cog belt or a 10-rib serpentine belt

  • Plane 3: Alternator and A/C compressor running on an 8-rib serpentine belt

Plane 1

The first plane is pretty simple because the oil pump’s cog belt is already in place and I have already purchased adapters for the cooling lines.

Plane 2

The idler and tensioner are mounted to the mechanical water pump. When it’s removed the serpentine. Given that the 8-rib belt, which has a very good wrap on the supercharger and damper, slips at almost 800-something HP it needs to be upgraded to either a cog belt or a 10-rib serpentine belt. I assume that the best solution is a cog belt that’s the same width (i.e., one inch) as the existing 8-rib belt. Given that I have no other accessories in the second plane, I have complete freedom to place the tensioner and idlers with a complete freedom.This means that I shouldn’t have an issue finding the right size belt.

If a cog belt isn’t desirable or feasible then I might have room for 10-rib belt, but that might push things too close to the chassis. Either way it would be nice to be able to change the diameter of the damper to change level of boost. To get to 1k HP I need to increase boost and I assume that I already have the smallest possible supercharger pulley. It’s not clear to me if that done with a subset of parts or if I have to replace the entire damper which is pinned to the crankshaft.

The Supercharger is from Harrop. As far as I can tell it’s a LS-Series FDFI Supercharger Kit. I have emailed them regarding alternative pulleys and the specs for the pulley that ships with the kit, but I haven’t heard anything back.

ATI’s Supercharger Super Pully looks pretty cool. You can read about it here. I know it’s designed for a much wider belt, but I assume that I run a smaller belt and perhaps machine some of the lip. It’s probably too big, but I’d like to see if it would fit.

Plane 3

The third plane runs the alternator and A/C compressor via a 6-rib serpentine belt. I had a custom 6-rib pulley machined that has a lip machined in it to index into the recess in the damper (see pictures below). I spec’d the 6-1/4” diameter to match Vintage Air’s recommendation for optimal drive ratio for the compressor. While the alternators pulley can be swapped out in matter of minutes, compressor pulleys have an integral clutch and can’t be swapped.

The alternator and compressor might be mounted as shown to the right.

The alternator is a high-end, custom billet unit described here.



Oil Pan

A great engine deserves a great oiling system so a three-stage Daily Engineering dry sump was added. These things are works of art. They are CNC machined from billet 6061 T6 aluminum. The oil pump bolts directly to the oil pan which eliminates the A/N lines between the oil pump and oil pan. All scavenge lines are internally machined into the oil pan eliminating the costly weight and expense of external scavenge A/N lines.

Dyno Run

When we added the Daily pan we had to change around the pulleys which meant that we weren't able to spin the supercharger as fast as we wanted. So for the second run we added a slightly bigger crankshaft pulley. If you compare the lower pulley in the pictures below you will note that the one on the right which was used for the second run is slightly larger which increased boost. This small change generated an increase of almost 100 HP. The amount of boost can be changed by varying the size of the crankshaft and/or supercharger pulley. The great thing about forced induction is that if you increase the boost you get more power so long as the engine can take it – and this engine can take it.

With the pulleys on hand we were only able to achieve 10.5 psi of boost rather than the 17 psi max. We also didn't spend much time tuning because the dyno was set up for a GM E67 ECU and the car will have a MoTeC setup. However, we still achieved some very respectable numbers: 842 HP and 818 lb-ft. With the proper pulleys this engine will produce 1000 HP. Note that in the videos below the engine looks a lot messier than the pictures above because the wiring harness, cooling lines etc. are all temporary. 


SPEC SHEET: LS7 SC 427 CI

  • Bore: 04.130"

  • Stroke: 4.000"

  • Displacement: 427ci/7.0L

  • Redline: 7,000 RPM

  • Horsepower: TBD hp

  • Torque: TBD lb-ft

  • CR: 9.0

  • Block: LS7 Aluminum (ARP main studs)

  • Crankshaft: Callies Dragon Slayer 4340 forged steel with ATI Super Damper

  • Connecting Rods: Oliver 4340 billet steel 6.125

  • Pistons: Diamond 2618 forged

  • Wrist Pins: .927 tool steel

  • Camshaft: Lingenfelter/COMP GT22

  • Cylinder Heads: CNC-ported LS7

  • lntake Valves: Del West titanium 2.205" diameter

  • Exhaust Valves: Ferrea 1.615" diameter

  • Springs: PAC titanium retainers and seals

  • lnduction: Harrop HTV 2300

  • Oiling System: Dailey 3-stage dry sump

Build Sheets

The block was purchased new and never had a VIN. There should be a serial number on the left side near the bell housing bolts. Brian and his crew provided the following build sheets:

Parts

  • Engine mount brackets; 3/8" x 2.3" shank

  • Suspension: 1.5" grip, 2.25+ length, 1/2-20

Qty.Part NumberDescriptionUnit Price
1 99-AKIT12279  Harrop Engine Cover Supercharger FDFI Series $454.00