MGB Engine Mastery: Building & Rebuilding Excellence

For many classic car enthusiasts across the UK, the MGB holds a special place in their hearts. Its timeless design, engaging driving experience, and relative simplicity have cemented its status as an automotive icon. However, like any cherished classic, maintaining its heart – the engine – is paramount to its continued enjoyment and performance. While the MGB engine is renowned for its robustness, decades of use mean that at some point, a rebuild becomes essential to restore its former glory. But who do you trust with such a crucial task, and what exactly does a comprehensive engine rebuild entail?

The Craftsmanship Behind MGB Engines: Who Builds Them?

When it comes to MGB engines, particularly for those seeking both road reliability and competitive edge, specialists are key. One such name that stands out with a remarkable legacy is Skiptune. With over 40 years of dedicated experience, Skiptune has been meticulously building MGB engines, catering to a diverse clientele ranging from daily drivers to prize-winning competition vehicles.

Their approach is deeply rooted in precision and customisation. Every Skiptune engine is a bespoke creation, built to order in their own workshops. This commitment ensures that each unit is machined to the highest possible standards, utilising only the best quality parts available. This meticulous attention to detail is what sets a specialist builder apart, guaranteeing not just functionality, but optimal performance and longevity.

Tailored Engine Solutions from Skiptune

Skiptune offers a versatile range of services to meet individual needs and preferences:

• Standard Road Engines: Perfect for the classic enthusiast looking for reliable, everyday performance that honours the MGB's original character.
• Fast Road Engines: For those desiring a more spirited drive, these engines are tuned for enhanced performance without compromising road usability.

The beauty of Skiptune's service lies in its flexibility. They can either build an entirely new engine for you, supplied as a complete unit ready for installation, or they can undertake the meticulous task of rebuilding your existing engine. Opting for a rebuild of your original engine is particularly appealing to owners who wish to maintain the vehicle's originality and provenance. Furthermore, if you already possess specific components – such as a cherished cylinder head or a performance camshaft – that you wish to incorporate into your new or rebuilt engine, Skiptune is pleased to accommodate these requests, integrating them seamlessly into the build process.

New Build vs. Rebuild: A Comparative Look

The Meticulous Process of an MGB Engine Rebuild

While the initial question might be about removing a cylinder head, the provided steps detail a comprehensive engine assembly process, typically following a full strip-down, cleaning, inspection, and machining of components. This is the heart of a professional engine rebuild, where every component is carefully fitted and torqued to specification. It's a testament to the precision required to bring an MGB engine back to life. Let's break down this intricate process:

Phase 1: Crankshaft and Main Bearings

The foundation of any engine is its crankshaft and main bearings, which support the crankshaft within the engine block. This phase is critical for smooth operation and durability.

1. Invert Engine: The engine block is positioned upside down to allow easy access to the main bearing journals.
2. Fit New Main Bearing Shells and Thrust Washers: Fresh bearing shells and crucial thrust washers (which control crankshaft end float) are installed into the block.
3. Install Crankshaft: The meticulously cleaned and possibly reground crankshaft is carefully lowered into its new bearings.
4. Fit New Shells to Main Bearing Caps: The matching new bearing shells are fitted into the main bearing caps.
5. Fit Main Bearing Caps in Block and Nip Up Bolts: The caps are placed over the crankshaft journals and lightly tightened.
6. Check Crankshaft End Float: This vital step ensures the crankshaft has the correct amount of axial movement, preventing binding or excessive wear.
7. Remove Caps and Individually Check Bearing Running Clearances: Each bearing's oil clearance is measured with precision, often using plastigauge, to ensure optimal lubrication.
8. When Clearances and End Float are in Limit, Coat Bearing Surfaces with Graphogen and Torque Up the Main Bearing Cap Bolts: Once all clearances are verified, bearing surfaces are lubricated with Graphogen assembly compound, and the main bearing cap bolts are torqued to their final, precise specifications.

Phase 2: Connecting Rods and Pistons

This phase involves assembling the piston and connecting rod assemblies and fitting them into the cylinders, connecting them to the crankshaft.

9. Fit New Pistons and Gudgeon Pins to Conrods: New pistons are carefully attached to the connecting rods using new gudgeon pins (or wrist pins).
10. Fit Piston Rings to Pistons: The crucial piston rings – compression and oil control – are installed onto the pistons using special tools to prevent damage.
11. Fit New Big End Shells to Conrods and Caps: New bearing shells are fitted into the connecting rod ends and their caps.
12. Place Engine on End: The engine is often stood upright to facilitate piston installation.
13. Insert Pistons into Cylinders: The piston and rod assemblies are carefully compressed with a ring compressor and gently tapped into their respective cylinder bores.
14. Invert Engine: The engine is flipped again to allow access to the big end bearings.
15. Check Running and Side Clearances: Similar to main bearings, the big end bearing clearances are checked, along with connecting rod side play.
16. When Clearances are in Limit, Coat Bearing Surfaces with Graphogen and Torque Up the Cap Nuts: Once clearances are confirmed, big end bearing surfaces are coated with Graphogen, and the connecting rod cap nuts are torqued to specification.

Phase 3: Camshaft and Timing Gear

This section focuses on the engine's valvetrain timing components, essential for proper valve operation.

17. Coat Camshaft with Graphogen and Insert into Block: The camshaft, responsible for opening and closing the valves, is lubricated with Graphogen and carefully slid into its bearings within the block.
18. Refit Engine Frontplate with New Gasket: The front plate, which covers the timing gear area, is reinstalled with a fresh gasket to ensure a seal.
19. Refit Camshaft Thrust Plate: This plate controls the camshaft's end float.
20. Fit Timing Chain Sprockets and Check They Are Level - Shim on Crankshaft as Necessary: The sprockets for the camshaft and crankshaft are fitted, and their alignment is checked, shimming the crankshaft sprocket if needed for perfect chain alignment.
21. Fit New Timing Chain to Sprockets and Fit to Cam and Crankshafts: A new timing chain is installed, connecting the camshaft and crankshaft sprockets.
22. Fit New Timing Chain Tensioner and Adjust: The tensioner is installed and adjusted to maintain proper chain tension, preventing slack and ensuring accurate timing.
23. Degree the Cam and Adjust as Necessary: This advanced step involves precisely setting the camshaft's timing relative to the crankshaft, optimising valve opening and closing events for performance.

Phase 4: Oil System and External Components (Front & Rear)

Ensuring proper lubrication and sealing is paramount for engine life.

24. Fit Oil Thrower to Crankshaft: This component helps to deflect oil away from the front crankshaft seal.
25. Fit New Oil Seal to Timing Chain Cover: A new front crankshaft oil seal is installed in the timing cover.
26. Refit Cover with New Gasket: The timing chain cover is reinstalled with a new gasket.
27. Refit Crankshaft Pulley with New Locktab: The crankshaft pulley, which drives accessories, is reinstalled and secured with a new locktab to prevent loosening.
28. Refit Engine Backplate with New Oil Seal, Gasket and Locktab: The rear engine backplate, often housing the rear main seal, is refitted with new seals and gaskets, and secured with a new locktab.
29. Fit New Rotors to Oil Pump (or Replace Oil Pump as Necessary): The internal components of the oil pump are renewed, or the entire pump is replaced if worn.
30. Refit Pick Up Strainer to Oil Pump: The oil pick-up strainer, which filters oil entering the pump, is reattached.
31. Refit Oil Pump with New Gasket: The oil pump assembly is reinstalled onto the engine block with a fresh gasket.
32. Refit Sump with New Gaskets and Main Bearing Cap Seals: The oil sump (oil pan) is refitted with new gaskets and often new seals for the main bearing caps, ensuring no oil leaks.

Phase 5: Cylinder Head and Valvetrain Assembly

The cylinder head, often referred to as the 'lungs' of the engine, is critical for combustion and exhaust. This phase brings the engine closer to completion.

33. Place Engine Right Way Up: The engine is now returned to its upright position.
34. Refit Cylinder Head Studs: If removed, the cylinder head studs are reinstalled into the block.
35. Fit Valves to Cylinder Head Using New Valve Springs: The valves are installed into the cylinder head, along with new valve springs, retainers, and collets.
36. Fit Head to Block Using New Gasket: A new cylinder head gasket is placed on the block, and the cylinder head is carefully lowered onto the studs.
37. Coat New Tappets with Graphogen and Insert into Block: The tappets (or lifters), which ride on the camshaft lobes, are lubricated with Graphogen and inserted into their bores.
38. Fit Pushrods: The pushrods, which transmit motion from the tappets to the rocker arms, are installed.
39. Reassemble Rocker Shaft with New Shaft, Rebushed Rockers and New Split Pins: The rocker arm assembly, including a new shaft and possibly rebushed rocker arms, is meticulously reassembled.
40. Fit Rocker Shaft Assembly to Head: The complete rocker shaft assembly is mounted onto the cylinder head.
41. Torque Up Head Nuts: The cylinder head nuts are torqued down in a specific sequence and to precise specifications, crucial for sealing the head gasket.

Phase 6: Final External Connections and Mounts

The final steps involve reattaching various external components necessary for the engine's operation within the vehicle.

42. Refit Oil Filter Extension with New Rubber Seal: The housing for the oil filter is reattached with a fresh seal.
43. Refit Oil Cooler and Pressure Gauge Connectors: Connections for the oil cooler lines and the oil pressure gauge are reinstalled.
44. Refit Oil Pressure Relief Valve: This valve regulates oil pressure within the engine.
45. Refit Distributor Drive: The drive gear for the distributor is reinstalled.
46. Refit Engine Mounts: The engine mounts, which connect the engine to the vehicle's chassis, are reattached.
47. Refit Flywheel with New Locktab: The flywheel, essential for clutch operation and engine balancing, is reinstalled and secured with a new locktab.

This comprehensive list underscores the complexity and the high level of precision required for a proper MGB engine rebuild. Each step is vital, and neglecting any detail can compromise the engine's performance, reliability, and lifespan. This is why entrusting such a task to experienced specialists like Skiptune is not just a convenience, but an investment in the future of your classic MGB.

Frequently Asked Questions About MGB Engine Rebuilds

Q1: Why should I choose a specialist like Skiptune for my MGB engine?

A1: Specialists like Skiptune possess decades of focused experience specifically with MGB engines. This deep knowledge ensures that they understand the unique characteristics, common wear points, and optimal specifications for these powerplants. They use high-quality parts, employ precise machining, and follow meticulous assembly procedures that go beyond what a general mechanic might offer, resulting in a more reliable, durable, and often higher-performing engine.

Q2: How long does an MGB engine rebuild typically take?

A2: The duration of an MGB engine rebuild can vary significantly depending on the specialist's current workload, the extent of wear or damage to your engine, and the availability of specific parts. Since Skiptune builds engines to order and focuses on custom specifications and quality, it's best to inquire directly for an estimated timeline tailored to your specific project. Quality work takes time, and rushing an engine build can lead to issues down the line.

Q3: What's the main difference between a 'standard road' and a 'fast road' MGB engine?

A3: A 'standard road' engine aims to replicate or slightly improve upon the original factory performance and characteristics, prioritising reliability and smooth operation for everyday driving. A 'fast road' engine, conversely, is designed for enhanced performance, often involving modifications such as higher compression ratios, performance camshafts, cylinder head porting, and carburettor tuning to deliver more horsepower and torque, making the car more exhilarating to drive. Both are built for road use, but the 'fast road' variant offers a more spirited experience.

Q4: Can I supply my own parts for the engine rebuild?

A4: Yes, as stated by Skiptune, if you already have components you would like to have built into your new engine, such as a cylinder head or a camshaft, they are pleased to accommodate this. It's always advisable to discuss this with your chosen specialist beforehand to ensure the parts are suitable and meet their quality standards for a complete, reliable build.

Q5: What is Graphogen, and why is it used in engine assembly?

A5: Graphogen is a high-performance, graphite-based assembly compound designed to provide initial lubrication and protection to critical engine components during assembly and the crucial first few moments of engine start-up. It helps prevent metal-to-metal contact before the engine's oil pump can establish full oil pressure, thus protecting bearings, camshafts, and other moving parts from premature wear during the initial dry start. It's an indicator of a professional and thorough engine build.

Conclusion

The MGB engine, a cornerstone of British motoring heritage, deserves nothing less than expert care. Whether you're seeking a reliable heart for your weekend cruiser or a powerful unit for competitive events, the choice of builder is paramount. Specialists like Skiptune, with their four decades of experience, commitment to high standards, and ability to tailor builds to individual specifications, offer a compelling solution for MGB owners. The intricate process of an engine rebuild, from the meticulous fitting of bearings and pistons to the precise timing of the camshaft, highlights the craftsmanship involved. Investing in a professionally built or rebuilt MGB engine is not just about bringing a classic back to life; it's about ensuring many more years of joyful, reliable motoring on the UK's roads and beyond.

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