Noonan Race Engineering Demonstrates Cylinder Head Repair

A few months ago, the EngineLabs Facebook page shared a side-by-side, before-and-after photo of a busted-up cylinder head repaired by Noonan Race Engineering of Australia. Due to differences in camera angle of the two pictures, many readers suspected a new head was used to show the after results. EngineLabs corrected the photo angles to clear up the misunderstanding, but Noonan promised to send start-to-finish pics of the next head repair that came into the shop.

Noonan is best known for developing the X1 billet cylinder head popular with Pro Mods and alcohol dragsters. One of its customers over-revved an engine using a different head, snapping a valve that carved up the combustion chamber. Some errant shrapnel also found its way through the manifold to another cylinder, again disfiguring the chamber surface.

The customer intended to upgrade to the X1 head soon, so he wanted just a basic repair to make the head useable for a few more races. Follow along the photos to see how machinist Alan McCoy and other technicians at Noonan Race Engineering repair the damage.

In chamber #1, piston-to-valve contact led to the valve head snapping and digging deep into the combustion chamber surface between the valve openings. In chamber #2, debris had moved through the intake manifold and scarred up the surfaces. Some of the valve guides were also bent.

The valve-seat inserts were removed and valve guides were replaced, as needed, on both chambers (this is #2). The chamber surface is also prepped for welding with a burr, then the insert recesses were machined for an undercut radius. This removes the sharp corner that could hinder the welding.

Here are the chambers after extra material is TIG-welded to the surfaces (#1 on the left, #2 on the right). Note that the insert recesses are also filled.

The chambers are then CNC-machined to near original dimensions.

Here's chamber #2 after the first round of machining. The insert recesses are machined and the valve-seat inserts are installed before the seats are machined.

Noonan double checks that the welds are 'clean and sound.' Noonan then fits the seat inserts and rough cuts the seats. The final CNC machining of the chamber and seat inserts ensures that the inserts blends into the chamber, and there's a final cut to correct the seat height. Shown are the finished chambers, #1 on the left and #2 on the right.

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
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