Holden Monaro Engine Rebuild with Mild Cam Upgrade

You don’t need extreme mods to get big results. With the right engine rebuild and a few carefully chosen upgrades, this Holden Monaro now puts down 370 rear-wheel horsepower—while remaining smooth, reliable, and easy to drive.

Aiming for Reliable Power

The car came to us with a clear goal: enhance performance without sacrificing drivability. The owner already had quality bolt-ons installed—Pacemaker headers, a 2.5” exhaust, and a custom intake setup. We added a mild cam and rebuilt the engine using high-quality parts, giving the car real punch without needing major gearbox mods or a stall converter.

Diagnosing the Core Issue

After 240,000 km, it was no surprise the Monaro was showing signs of fatigue. Oil pressure was down, and compression was low in cylinders two and seven. A wet compression test confirmed worn piston rings. The customer opted for a full rebuild, giving us the opportunity to build a solid, long-lasting engine foundation.

Engine Rebuild Process

We removed and stripped down the engine, then inspected and measured key components. While everything was in decent condition, wear was extensive, so machining was required:

• Block: bored and honed to 0.010” oversize

• Crankshaft: reground to 0.010” undersize

• Cylinder heads: de-carboned, valve seats recut, and resurfaced

Camshaft and Component Selection

The camshaft selected was a Crow Cams 871275, a street-friendly grind focused on mid-range power. It pairs perfectly with the stock automatic transmission and supports a broad RPM range of 1800–6200.

Camshaft Specs:

We matched the cam with:

• Crow conical valve springs (4231-16)

• Delphi roller hydraulic lifters

• Crow single row timing chain kit

For the bottom end, we stayed close to stock spec:

• Clevite bearings (0.010” undersize)

• Melling standard oil pump

• Speed Pro pistons (0.010” oversize)

• Hastings piston rings

Everything was sealed with an AA Permaseal gasket kit using steel head gaskets.

Supporting Components

The car already had great airflow thanks to Pacemaker headers and a custom MAF-less intake. These were retained and complemented the build perfectly. We added:

• NGK spark plugs

• Bosch leads

• Ryco oil and fuel filters

• Gates drive belt and tensioner set

Final Tune and Results

Once everything was installed and tested, we sent the car to Tremaniac Racing for tuning. Aaron dialled in the setup to perfection, achieving 370 RWHP with smooth, usable torque throughout the rev range. The result is a car that pulls hard from just above idle and stays civilised on the road.

Summary

This Holden Monaro build proves that power and drivability don’t have to be a trade-off. With smart component selection, expert machining, and a quality tune, we created a balanced street car that feels as good as it goes.

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.