Request options for the LS3 Engine
#25558 from Butch Kummer · Rule change · TB 19-01 (2019-01 Fastrack)
In GTA, GCR section 9.1.2.G.IX, add new engine spec as follows:
• GM “604 Circle Track” engine as defined in Appendix G.
• GM LS3 engine as defined in Appendix H.
“Appendix H: GM LS3 Engine.
H.0: Must meet all requirements listed in Appendix A.
H.1: A stock Mass Air Flow (MAF) sensor, GM part #2516 → 8491, or #1586 → 5791 must be used.
Any commercially available air filter may be used. All tubes between the air filter and throttle
body must be metal (except unions used to connect intake tubes). The maximum outside
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diameter of the tubes is 4.0 inches. No tapered tubing, tapered inserts, or airflow directing
devices may be used in the tubing connecting the air filter to the throttle body.
H.2: The throttle body must be either a GM 90mm, electronic, part #1257 → 0790, or Edelbrock
90mm, mechanical, part #3869.
H.2.1: Throttle bodies may not be modified.
H.2.2: A 2.150 inch diameter flat plate restrictor must be in place during all practice,
qualification, and race sessions. The restrictor must be mounted in the inlet side of the throttle
body.
H.3: An unmodified LS3 GM (short), or L92 GM (tall) intake manifold must be used. Identically
equivalent GM part number intake manifolds may also be used.
H.4: Unmodified GM LS3 cylinder heads, GM casting #’s 0821, 0823, or 5364 must be used.
Porting and/or polishing is not allowed. No more than a three angle valve job with a bottom cut
of 60 degrees is permitted. A maximum of 0.250 inches from the head of the valve seat to the
bottom of the 60 degree bottom cut is allowed. No grinding in the combustion chamber bowl
area is allowed. No interior or exterior coatings are permitted. Valve covers are unrestricted.
H.5: The maximum compression ratio is 10.7:1.
H.6: The spec TA2 LS3 camshaft must be used. The cam must be ordered through Schwanke
Engines, (507.723.4120). Stock rocker arms, with a 1.7:1 ratio must be used. Stock valve
spring retainers and keepers (locks/keys) must be used (no titanium). Any valve springs are
allowed.
H.7: The stock engine bore is 4.065 inches (103.25 mm). Cylinders may be honed as part
of the normal freshening procedure, but the engine displacement cannot exceed 378 cubic
inches.
H.8: The stock crankshaft, with a 3.622 inch (92 mm) stroke, must be used.
H.9: Aftermarket pistons, piston rings, piston pins and connecting rods may be used if the
basic design and weight is the same as the stock GM components.
H.10: Aftermarket fasteners, including rod bolts are allowed (no titanium).
H.11: The oil pan is unrestricted, but the oiling system may not exceed a four-stage system
(three scavenge and one pressure).
H.12: A GM ECU must be used. It may be re-flashed and the maximum RPM set at 6800
RPM.”