Holden Monaro LS1 Performance Build

Holden Monaro LS1 Performance Build

With this build we achieved 370 RWHP with just a mild cam, a top-quality tune and the existing headers and air intake mods already on the car.

With this build we achieved 370 RWHP with just a mild cam, a top-quality tune and the existing headers and air intake mods already on the car. This a great example of how you can get a drivable and flexible performance package. Just by starting with a good quality engine rebuild and adding a few modifications in just the right places.  The result is a car that pulls strongly from just above idle, doesn’t need a stall converter or other gearbox mods and makes very good power.  Here’s how we got there.

A few weeks back we received this pristine Holden Monaro into the workshop for a cam, lifters and valve springs.  Also on the job card was a good reco of the heads and possibly a new oil pump.  First step was to check oil pressure and cylinder compression.  As the owner had suspected, oil pressure was down.  And after 240,000 km on the clock, compression was down in cylinders two and seven as well.  Retesting after squirting a little oil in the cylinders restored compression, confirming excessive ring wear as the cause.  We reported the results to the owner and after some thought, he settled on a full rebuild.

After removing, stripping down and cleaning the engine, we measured up the bores and crank.  Both were in good condition but excessively worn from all those kilometres.  So, the block was carded up for a bore and hone to 0.010” oversize and resurface the decks. For the crank, a regrind to 0.010” undersize.  Heads were also in good condition, so they were carded for the usual de-carbon in our bead blaster, recut the valve seats and valves and a resurface to bring them back to as-new condition.

Next came component selection.  Camshaft had already been agreed as Crow Cams part number 871275.  Crow describes this one as a “street cam with good mid-range power”. We selected this one as we felt it would match well with the standard auto and maintain drivability, yet still give a good lift in performance across the rev range.  See below for the cam specs.

RPM Range   Part No.  Adv. Duration  .050″ Duration Valve Lift  LSA  Lash Intake Lash Exhaust
Intake   Exhaust  Intake Exhaust   Intake  Exhaust
1800-6200 871275 300 292 217 224 .528″ .527″ 114 HYD HYD


We matched the cam with Crow conical springs (#4231-16), Delphi roller hydraulic lifters and a Crow single row timing chain kit.

With the cam limiting the effective rev range to just a little above stock, we stuck with pretty much standard spec but high quality parts for the rest of the engine.  For the bottom end we went with standard spec Clevite main and big-end bearings at 0.010” undersize, a Melling standard volume oil pump, cast Speed Pro pistons at 0.010” oversize and Hastings rings.

To seal the whole thing up we used an AA Permaseal gasket set with steel head gaskets.  New NGK plugs, Bosch leads, Ryco oil and fuel filters and a Gates drive belt and tensioner set completed the package. The car was already fitted with Pacemaker headers, 2 ½” exhaust and a custom ram-style air intake system without the mass air-flow sensor.  These were a nice complement to the engine so were retained with the final build.

Following install and testing, we sent the car off to Tremaniac Racing for the tune, and Aaron delivered just the result we wanted, 370 hp at the rear wheels with a nice smooth power delivery.  Just as importantly, loads of low-down torque to deliver that pressed against the seat feeling from the moment you get on the throttle.

Our thanks go to Aaron for the tune and of course, the owner Steve for trusting us with his pride and joy.

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