engine block Archives

Metal Stitching an Engine Block from 1921 in-situ!

26th November 2022

1921 Duesenberg Model A

We do a lot of in-situ work. We routinely carry out machining and metal stitching work, among others, on components that are too large to be moved to a workshop or where dismantling work is too time consuming or costly. But repairing a an antique car engine block, in the chassis, in a museum, is still quite special. Even for us.

The engine in question is an in-line, eight cylinder one with a bore of 72 mm and a stroke of 125 mm (2.875″ x 5″). With a swept volume of 4’256 cc, or 260 cubic inches, this early Duesenberg Model A engine is capable of producing up to 88 hp (66 kW) of power.

Repair in progress. The engine remained in the chassis, only the cylinder head was removed.

We got the opportunity to work on this engine as cracks had began to show at the corners of the engine block. The cracks originated from the threaded bores housing the cylinder head studs. They extended towards the outside of the engine block on one side and into the cooling water passage on the other.

The fact that the engine was left inside the chassis made the repair a little more challenging than usual. Our metal stitching expert had to use a mirror for much of the repair work. Without it he could not see, let alone repair the cracks at the rear end of the engine block. In addition to sealing the cracks with stitching pins, our expert also installed Full Torque™ thread inserts at the threaded bores. Unlike conventional thread repair inserts, Full Torque™ inserts do not create spreading forces. They are therefore the perfect solution for cases like this one, where threaded bores close to an edge have to be repaired.

Cracks extending from the cylinder head stud bores to the outside and to the cooling water space

Installation of Castmaster stitching pins. They are the strongest and most advanced stitching pins on the market today.

Ultrasonic inspection of the casting to determine the wall thickness

Metal stitching in progress. Due to the location of the crack a mirror was used.

The completed repair. Cracks stitched and Full Torque thread inserts installed.

Links

Metal Stitching

Metal stitching is a very well-established repair method. It is applicable to a wide variety of materials such as cast iron, cast steel and many non-ferrous metals.

Thread Repair

The repair inserts that we use to repair damaged threads are super strong and do not create spreading forces. They are ideal for high-load applications.

Metal Stitching a Fractured Engine Block from 1913

25th November 2022

Pierce Arrow

This post describes the repair of a Pierce Arrow engine block from 1913. The Pierce Arrow was the largest production automotive engine at its time. The swept volume of this 6-cylinder, 48 hp (36 kW), engine amounts to a whopping 13’500 cc (824 cu in)!

This engine is of the T-head engine type, which is essentially an early form of crossflow engine. This design is characterized by two separate camshafts, one on either side of the cylinder. One camshaft operates the inlet valves and the other the exhaust valves. This makes this engine design quite complex and expensive to produce.

The main advantage of the T-head engine design is the fact that it is not at all prone to knocking – a condition where the gasoline vapour in the cylinder ignites too early by itself due to compression, before it is lit by the spark plug. Knocking was a big issue especially during the early decades of the 20th century, when gasoline sold typically had a very low Octane rating. T-head engines were therefore popular until about 1920, when better fuel became widely available. At that time, the disadvantages of the design started to outweigh the advantages.

A large piece had broken off the cast iron engine block and had to be reattached

The in-line 6-cylinder Pierce Arrow cast iron engine block that we received for repair at our workshop at Lock-N-Stitch in California, USA, was severely damaged. A large piece of the casting had been broken off at the block’s front (timing belt) end.

Our metal stitching specialists successfully reattached it. In order to do so, they installed about thirty Castmaster™ stitching pins over a total fracture length of 160 mm, in material with a thickness ranging from 12 – 16 mm. For additional strength, they also installed two high-strength locks perpendicular to the fracture line.

The fracture line passed through a hole for a positioning dowel pin. To repair that, our specialists first closed the hole by installing a solid Full Torque™ plug, before drilling it anew in the exact location.

Repair completed. Stitching pins, locks and Full Torque insert installed

Repairing a V12 Flathead Engine Block from 1934

2nd November 2022

Packard Twelve

We routinely work on museum pieces. In this post we introduce a typical case: The repair of a Packard Twelve engine block from 1934, carried out by our colleagues from Lock-N-Stitch in California.

As the name implies, the Packard Twelve is a 12-cylinder engine. It is a flathead engine, sometimes also called side-valve engine, where the intake and exhaust valves are contained within the engine block rather than within the cylinder heads. Flathead engines were very popular until the 1950s and were built in large numbers by automotive manufacturers. Their advantage is their simplicity, compactness, reliability and low cost as the flathead design obviates a complicated valve train. Such engines therefore need far less components than alternative designs such as, for example, single or double overhead camshaft arrangements.

The main disadvantage of the flathead engine is its relatively low efficiency and power output. The Packard Twelve V12 engine has a displacement of 7300 cc (445 cu in) and a maximum output of 119 kW (160 hp).

Engine block received with cracks in both longitudinal side walls and around the valve seats

Repair of cracks in the side walls of the engine block

When the engine block was delivered to us, it contained eleven cracks of various lengths. Some were small, others rather long. Added together, they amounted to a total length of 200 mm. In addition, the block suffered from corrosion and material loss around the camshaft spaces.

The cast iron block had been “repaired” before by arc welding. This has not been a great success – new, fairly large cracks could be seen extending to the left and right of the weld.

As they always so on cast iron parts on which someone has already been attempting a repair by welding, our specialists cut out all material in the vicinity of the weld, in the so-called heat affected zone. This is our standard operating procedure. Whenever cast iron is welded at, the heat from welding burns out the carbon, which constitutes between 2% and 4% of the cast iron. Once the carbon is burnt, the cast iron becomes hard and brittle, looses its structural integrity and becomes worthless.

To replace the cut out material on both longitudinal sides of the block, our specialists installed repair patches made of cast iron. They stitched them firmly in place with Castmaster™ stitching pins. Similar pins of various lengths and diameters were also used to repair the cracks found in various locations on the block, in material ranging from 3 – 10 mm thick. Some of these cracks are visible in the pictures below.

Our specialists also installed five Full Torque™ thread inserts to repair thread holes damaged by corrosion and erosion.

The engine block had been arc welded in the past. As expected, this did not solve the problem but led to further cracks extending left and right. — The engine block has been arc welded in the past. As expected, this did not solve the problem but led to further cracks extending to the left and right of the weld.

Crack extending leftward from the weld, serious corrosion at the edge of the sealing surface.

We removed the material that has previously been welded and installed a repair patch.

Crack extending rightward from the weld. Again, serious corrosion at the sealing surface. — Crack extending rightward from the weld. Again, serious corrosion at the camshaft cover sealing surface.

Installation of stitching pins to seal the crack

Skimming of cylinder head landing surfaces

Repair of cracks around the valve pockets

A thorough magnetic particle inspection (MPI) of the block revealed hairline cracks between some of the valve seat and cylinder liner bores. We permanently repaired these cracks by installing small size stitching pins.

After completion of the repair, we took the opportunity to skim all cylinder head gasket mating surfaces, on the engine block as well as on the two cylinder heads.

Crack between valve seat and cylinder bore clearly visible during Magnetic Particle Inspection (MPI)

Cracks between valve seat and cylinder bores successfully repaired

Another crack, seen here under Ultraviolet (UV) light during MPI

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