Posted by Iain Litchfield on 30th November, 2017
in GT-R, Nissan
We thought it might be of use to explain what goes into one of our GT-R engine builds as many customers are looking for either repair, take preventative measures or simply would like to have more power than the standard engine will take.
This article will hopefully explain in more detail some of what we have learnt over the years, why we do things the way we do and what we feel it takes to ‘Blue Print’ a GT-R engine correctly.
There is so much detail that goes into even our entry level Litchfield 3.8 engines and that is before we get into the extra work and parts that go into our Sport and Red Top engines.
Stripping down, cleaning and rebuilding a GT-R engine is no more complicated than any other engine. The weakest components, like most engines, will start with the connecting rods and pistons. Replacing these will allow an engine to greatly increase its power and there are a huge number of manufacturers producing stronger components to meet this demand. However like most jobs there is what can be done cheaply and easily then there is the right way!
Having been through the pain of poor block/bore strength and piston problems with other engine designs over the years we under took GT-R engine building with a clear approach and with considerable amount of hard learnt knowledge.
Fundamentally we want to do as much if not all the engine machining and assembly work in-house. When relying on outside firms you can’t guarantee the workmanship, the pressures they may be under or the quality of the machines used. When things inevitably go wrong everyone is quick to point the finger and the outcome is usually the same.
Having our own machine shop allows us to perform the right machining operations rather than what is cost effective or good enough.
When we build an engine that can achieve the kind of power the GT-R is capable of we only want to use the very best components manufactured to our specifications by the finest Motorsport companies. These engines have our name on them and we warranty their quality.
Steve torquing down cylinder heads on a GT-R Engine build
GT-R engine blocks in our dedicated clean room
Whilst all our technicians are capable of ‘building an engine’ we know that when it comes to something so important we require dedicated experts in this field.
Steve is our head engine builder and has over 35 years of engine building and engine machining experience. Like his engine builder father before him, Steve has been creating amazing championship winning engines throughout his whole career and joined the Litchfield team full time back in 2013. Since then we have expanded our facilities and invested heavily in building a dedicated engine machine shop and cleaning room to complete all these critical operations on site. We are therefore in full control of every stage of the engine build process and can guarantee the quality of the work.
Working alongside Steve is Sam, a Motorsport Engineering Honours graduate, who has a passion for all things motorsport and a healthy level of the OCD required to build exceptional engines. Along with senior Master Technicians Ryan, Stuart and Scott we have a team of trusted enthusiasts that insure each engine is assembled with the care and experienced needed to produce an engine we are proud to carry our name.
Making The Grade
The gap between the piston and the side of the bore is critical to allow an engine to make power, reduce friction, noise and manage oil consumption. Nissan grade the size of each of the GT-Rs bore and stamp this on the outside of the block so they can choose the correct pistons to suit the bore.
There are plenty of companies that will sell “drop-in” or “graded” pistons but unfortunately they don’t work or if they do they won’t work in the long run. We’ve tried and tested most over the years and whilst it became a more expensive and less profitable route we decided the only way was to develop our own pistons, even in engines that did not require as much power. It is better to do things the right way to begin with than have potential warranty issues down the line.
Litchfield Nissan GT-R Piston
Litchfield / Capricorn GT-R pistons installed in a block
The theory behind Nissan’s bore sizing is fine in principle but if you measure a new or used block the grading’s can be crude at best and often you will be able to measure distortions and ovality down the length of the bore. Selecting a “graded” piston therefore simply can’t take into account these inaccuracies and the engine will end up with varying piston to bore clearances which will cause excess wear on the rings and lower performance because of increased blow-by and reduced compression.
Even with the correctly fitting pistons and re-honing cylinder liners we can see a significant change in bore ovality when the cylinder head is clamped down and the block is stressed with the head bolts.
Many of the aftermarket pistons also use the incorrect piston rings with Nissan’s Plasma bore finish which can further increase wear, oil consumption, breathing issues and ultimately reduce engine performance. We regularly see engines which under perform and this is almost certainly down to incorrectly fitted pistons or poor quality rings.
To resolve this problem we have machined the engine block to suit our custom pistons rather than the other way around.
We have produced our own sets of “Deck Plates” which are solid aluminium blocks that are designed to simulate the cylinder head and allow us to apply the same clamping pressure to the block. Once installed the plates are left over night at a controlled temperature. The next day the bores are measured for ovality and distortion with the plates in place.
Using our Delapina honing machine, which until the end of 2016 was performing these operations for a well know F1 team, we are able to machine out the imperfection from the bore. As well as requiring the correct machinery this is a very time consuming, skilled operation but essential to set the correct foundations for our high performance engines. With the bores sized to suit our pistons we can be sure the correct clearances are maintained throughout the bore. In fact the bores will now change shape slightly when the plates are removed but will return to a perfect round finish when the cylinder head is reapplied.
The Nissan block uses a cradle to secure the crankshaft in place and these are produced as a matched pair. Over time the crankshaft journals can move and wear so to insure a perfect seating position for the crank bearings we ‘Line Hone’ these mounts so they are once again true. We perform the same process when we match our stronger billet cradle to a new block.
Nissan GT-R crankshaft main bearings table
Like the connecting rod bearings, Nissan produce a huge range of crank bearing sizes to allow each engine to have a unique and perfect crank set. Nissan’s bearing sheet is a prime example of the lengths a manufacturer will go to insure their engines perform and continue to perform for as long as possible.
The aftermarket can supply bearings in 2 sizes, standard and oversized. I’m sure if Nissan felt they could produce a ‘one size fits all’ bearing they would be using them out of the factory. The obvious answer is they can’t and again we have seen engines with crank/oil pressure problems which will be the result of incorrectly matched bearing clearance. They will work in short term as the material used will wear in but ultimately they will wear out. As a business it would be much cheaper and easier for us to stock just one size of bearing on the shelf but again there is the right way.
All our bearings are graded and matched to the crankshaft once it is balanced and cleaned.
Litchfield Engine build store room
How Clean is Clean?
From start to finish we take cleaning and preparing our GT-R engines very seriously. This is more than a tidy area in a corner of a workshop but a carefully thought out system to help us enhance what we can offer. We have purpose built our facility with this in mind with each main process having a separate area to reduce cross contamination.
Litchfield Engine Build Clean Room
Once the engine and ancillaries are removed within the main workshop the engine is moved onto a stand and wheeled around to our strip down area. Here the engine can be broken down to component form before initial cleaning and inspection. Excess oil and grime are removed from the components in a traditional cleaning tank.
Litchfield Hot Wash Tank
Ultrasonic cleaning a Nissan GT-R cylinder head
Once this first step is completed the parts are moved over to the hot wash tank. Like a super-sized dish washer our cleaning tank washes all parts in a spinning bed with special cleaning chemicals. After 30mins the parts come out almost like new with the deeply ingrained grime all washed away. Once cooled down the parts are laid out on work benches so we can give them a proper inspection before moving over to the machine shop.
Once all the machining is complete the excess metal and swarf is cleaned off before the parts are returned to the hot wash tank. This removes most of the remaining particles but we have a further stage that insures even the hardest to reach areas are cleaned like new.
The components are then submerged inside our ultra-sonic cleaning tanks where the hot cleaning solution is agitated at different frequencies for up to an hour at a time. This breaks down any remaining particulars and most importantly gets to areas where the normal hot wash tank pressure cannot reach.
The final step sees these reconditioned parts moved into our dedicated clean room. Here we only have new or cleaned components laid out for assembly. The roof uses constant dust extraction and filtration to keep it as clean as possible. Here we can assemble the new engine in a clean and sterile environment and with the doors closed it is a peaceful room free from the distractions of a busy workshop.
Piston Crown Design
We have evolved our Piston crown design over the years and this has seen improvements in power and efficiency within our engines. Most piston designs mimic the original shape but use a stronger material. This obviously works but the requirements of a cast production piston running in an emissions conscious engine are different to a performance orientated design.
Our pistons have a revised shape and we were able to test not only power and torque improvements on our dyno but also check the efficiency of the combustion through logging and measuring the real time emissions with our 5 gas analyser. We can also see after stripping engines back down that the combustion is more complete meaning the redesigned piston crown extracts more energy. When combined with our combustion chamber changes we are also able to decrease the engine knock characteristics which means we can run more ignition timing. When an extra degree of spark advance can be a considerable amount of extra power (+15-20bhp on standard engine) this can have a real impact on performance.
Litchfield / Capricorn Nissan GT-R Pistons
Our pistons also feature anti-detonation bands which also help reduce knock/pre-ignition and to further support the piston rings the top of the pistons feature just the right sized “Gas Port” which helps the top ring maintain compression during the combustion phase. The higher and more stable the compression ratio the more efficient the burn phase will be.
All our engines have substantial machining and preparation work completed on the cylinder heads. There is nothing stopping the standard cylinder heads being put straight back onto an engine with upgraded pistons and rods, it will work but it will be sub optimal.
When we work on an engine each component in the cylinder head is stripped, cleaned and checked. The combustion chambers have extensive machining to re-profile the squish angles for our revised pistons and this has been dyno proven to produce more power compared the standard design.
Each valve seat is recut with a specialist machine to correct the valve alignment. Each valve is checked for length & straightness before being lapped by hand so that their closed position creates the right seal and enhances compression.
GT-R Cylinder heads ready for machining
GT-R valve measuring
Steve carefully refinishes each of the ports allowing the engine to breathe more easily and reduce airflow disturbance from blunt edges and casting intrusions. The cylinder head faces are also machined in-house to remove any distortion that occurred over time, insuring a perfect fit.
GT-R cylinder heads being machined on lathe
GT-R cylinder heads before machining the faces flat
With the valves installed the individual inlet and exhaust valve buckets are re-shimmed to get the correct clearances and reduce wear. We carry over 60 different Nissan bucket sizes in stock, but even then Steve will often be found making minor adjustments to get the perfect clearance.
60+ GT-R buckets
Without wanting to go into all the areas that we have learnt to improve over the years we do make some important modifications to other engine parts. Essential items like the Variable Valve Timing (VVT) units are improved and the engine oil pump is modified and blue printed to name a few.
To complete the engine we strip, clean and re-powder coat the engine covers which gives a more durable, deeper finish than simply painting. The Rocker covers are finished in a dark metallic grey to give a classy look and avoid corrosion. We also offer the option of custom colours should you want a more individual engine bay.
As I hope I have shown, there is more to building a GT-R engine, even our entry level unit, than just installing stronger components. To get the best performance you need to consider all the small things that add up to creating an engine we and our customers can be proud of.