Guy Croft Performance

A few words from Guy himself about twin cam engines. 

Guy Croft

Q: You are considered to be an expert on Lampredi's DOHC engine. Why did you choose this engine? There are lots of other excellent engines, stronger ones too, but you chose this iconic inline-4 as your area of expertise. Why?

A: In the mid 80s I had some work done on my Gp3 Fiat-Abarth Spider engine. The firm doing the engine was owned by two ex- F1 guys (as I am now myself).I asked them how one could become a race engine builder and they said you need to pick an engine and become expert with it. They suggested that if I went down that ‘career’ route the Fiat TC would be a good choice as it was a great engine and no-one outside Italy was really doing them.

I’d first encountered the Fiat TC in the mid 70s - on the cover of the famous book by Bentley Publishing ‘Design and Tuning of Competition Engines’ - which was pretty-well the only book I read at university. The more I played with my own cars – a series of Fiat 124 Sports and then the 124 CSA which I bought from a Director of Lancia in 1983 the more I thought ‘yeah, this is a great little motor’ and kinda fell in love with them. In recent years I’ve done countless other types and would say it’s in a class of its own. Nothing comes close.

Q: Everyone would like to have as powerful engine as possible in their cars. Is this approach correct?

A: Nah. I get this all the time. For a start most of the folk who want high power have never actually experienced it and it would be dangerous in their inexperienced hands and irresponsible of me to give it to them. For the newcomer or novice it’s far more important to have a well-prepped car with a really robust installation (good cooling, fuel and lubrication system, the right clutch and so on..) than loads of power. Motorsport is punishing on the car and engine and they rarely appreciate this. I make it my mission to educate them (in the nicest way) about all the things a well-sorted competition car has to have. Mostly they say, ‘wow, I never realised I’d need all that!’

Those who go for all-out power need to be very experienced. When you can consistently drive balls-out on the throttle or rock-hard on the brakes – with no in-between – you have mastered the car and engine. It takes a long time to get used to a new engine with more power and until you are driving on the ‘limit’ all the time you ARE NOT ready for more. 

Some think for example that 200bhp from a Fiat 2 liter TC is unimpressive. Believe me it’s not. I’m one of very few who have actually produced that from the 8v unit and I’ve sat in a professionally-built spaceframe short-oval NHRA car and been driven by a top international driver round a circuit. That was a guy who knew how to drive consistently flat-out all day long. That 200bhp was utterly terrifying to experience in action. I nearly got flung out thru the net on the passenger window the G force was so immense; my hands lost all their strength. He had to grab me by the leg and slow down to keep me in the car. 400bhp from a turbo unit is a pussy by comparison – a highly tuned 8V TC atmo unit is a sight to behold. 

Money is always tight. You have to have real first-hand experience to be a good race engine builder. If money is ‘tight’ I’d trade a mega-powerful engine for a close-ratio gearbox or a better installation every time. I can say that because I know it’s true, it’s not something I just read in a book. I’ve seen the very best and the very worst. Even the best will crash. Everyone who rallies or races will sooner or later and it’s usually too much power to blame. Add inexperience to huge power (and I know how to do it) and throw in a badly prepped car and you’re going to die.

There are a few sanguine folk who understand this but they are few and the newcomers are the worst. I make it part of my job to talk to people to get to know them a bit and tell them what they really need! Sometimes it’s not a new engine! That’s often not what they want to hear, but I know competition drivers all over the world and I do get hear about the blow-ups and crashes (sooner or later) believe me!

Q: Where building an engine starts? Is it planning the performance and suiting it to customer`s needs, budget and the car? Please tell about this process.

A: What is it for? What’s car? Is there an outline budget (1/3 of the overall cost of the whole car should always be devoted to the engine)? 

The drive ratios really determine where you put the power-band (eg: 4500-7500) and once that is decided if you drive outside the powerband you got it wrong and there is nothing I can do because it tells me what kind of engine tuning mods to do. The rest is about ops and parts – race rods and pistons and stuff to stop the damn thing exploding which is in the nature of competition engines really.
I will write up an exhaustive estimate that covers the build right down to last nut and bolt and also ID all the ancillary equipment needed. This is very time-consuming to do and it’s only possible at all because I have a mental picture of everything in my head! That estimate becomes the aide-memoire for the build – it’s written in the build sequence, starting with strip and preliminary clean and finishing with assembly. 
The client has to pay me to write this – it can run into 6 pages of top-technical stuff with advisory notes too and it often takes me more than 5 hours. That’s with all my years of experience I might add. Usually I offer it at 2 hrs so it’s not a bad deal, 2hrs of Crofty’s brain-power for their exclusive engine. I send it off marked up for ‘client review’ and then once he’s read it we discuss alterations to the spec on performance or cost grounds. One thing I never give way on is items that affect reliability. 

You can imagine most folk won’t pay because they want a ‘list price picked out of thin air’. It’s not like that in my firm – every single engine is different and so is every budget and the installations and even the cars vary (much of what we produce doesn’t even go in Fiat cars) and I could  never offer a standard ‘list price’. Only firms doing one-make series can do that. 

I heard many times that someone had taken an estimate and phoned everyone else who reckoned they knew about Fiats saying ‘Guy Croft wants £XXXX what can you do it for? There aren’t any people in the world who can do GC engines – they might do their own but it won’t look like GC work (nothing like) and it won’t go or last like GC stuff. Paying for a GC estimate has stopped that. I don’t get the job that is time lost – and time is at a premium here, so I try to ‘read’ the client before engaging with him and having that protocol saves a lot of dreaming and messing.


Q: How your engines are built? How many people work on one engine, how long it takes to build one?

A: I build all ‘GC engines’ personally. Hence the name. I put them together. I started this firm about 12 years ago and work entirely on my own; apart from balancing cranks and some machining ops I do everything myself in-house. That’s hard work, I assure you and there is a lot more to running a firm like this than just playing with shiny things. Getting even the basic things like main bearing caps and housings deburred and dressed and cleaned and ready-to-fit itself takes hours and hours. It takes 3 days or so (depending on interruptions) to prep a race head even on standard sized valves. If it’s a big valve conversion a week or more. It takes near days to rebore and fully prep a block, a day to do a crank to race standard and so on…
Parts for a build are allocated direct from stock when we have them but often there is a wait for rods and pistons which I design myself and have made in the USA. The fastest I can put an engine together with all the head mods and other machining – if I have all the race parts to hand – is 10 days, but you can’t do that every day because the profit margin on an engine is not enough to justify shutting the firm to everything else for that period: And it would bring the entire operation to a complete halt! I would not be able to sit here and write this for a start or deal with the countless phone calls and emails the firm receives every day! 
In the main I tell clients it will be months not weeks so they need to get in around autumn if they want to compete the following year.

Q: How customer can be sure of final product he gets for a money? Is there any warranty, engine comes power-tested, and you provide maintenance tips?

A: Haha! It’s the other way round – can I trust the client?! Why? Because in the case of almost every engine I ever did that exhibited a problem (and there have not been many) was caused – literally – by the client. Either because he did some knowingly stupid (like re-using old coolant hoses or wrecking the clutch during fitting by hanging the gearbox off it) or due to complete ignorance! 

I don’t blame folk for not knowing the things I do about installations and start-ups and ancillary stuff like exhaust system layouts but I do object to people not reading the data they get with engines or listening to what I tell them. I go to ridiculous lengths to brief folk by word or writing endless GC ‘How To’ data sheets on even the simplest things (like 3 paragraphs on how to fit the clutch!). One of the things you have to cope with as a race engine specialist is that it will always be portrayed by the client that it is ‘your fault’ or that you ‘never told them that’ which is one very good reason we don’t do engines for road cars anymore! No GC engine carries a warranty. GC engines are build to the highest standards of physical perfection and if one goes wrong the client must bring it back to me for inspection. This is written into the terms of sale and you have to do it that way when you are shipping things halfway round the globe. That said I don’t want things going wrong and the standards I impose here even on myself -  with the most stringent quality-related techniques and methods - would really make your eyes water! 

I rarely dyno test these days and frankly don’t need to. I did hundreds of hours in the 90s and can remember every spec and setting I ever did. Many of my clients got to rolling roads of course. I have started in-house run-ups (but off-load) to prove out the integrity of the engine systems – cooling and oil and ignition & fuel settings. I’ve never had my own dyno, much as I would love to have one I never, ever had that kind of money and they cost a fortune to hire.

Q: What is average cost of twin cam by Croft? Let`s say a rally spec 2.0 liter twin cam?

A: If you have to ask you can’t afford it! Sorry. Anyway every one is different and those GC prices are confidential between me and the owner. Seriously, no two are alike nor are the lists of ancillaries like oil system or instruments. However in summary if you have $10,000 in your account we can probably work for you and if you want to spend less than $6k we won’t be working for you. Not on a full engine anyhow. But that said we do more heads than full engines and a heck of a lot of mail order kits of raceparts for guys who want the experience of ‘having a go’ themselves and I am all in favour of that.

Q: What are the most popular specifications the customers choose?

A: Two liter 8v twincam in the 170-185bhp range for rally. Old-fashioned ‘Works Replica’ stuff with carbs and distributor. 

Q: What would you consider your most challenging/interesting project in engine building? What are the details?

A: I spent a period working for Brian Hart (Hartpower) during 1997-1998 as an F1 engine builder on Minardi and Arrows engines. Seriously, after that nothing challenges me anymore with engines. Those were £80,000 engines and the minute they were finished they went on test. There, with my engine previous experience I found myself working on my own (usually we worked in pairs) on his engines within weeks when my time-served F1 build partner went on holiday. That is pretty scary! 

The most ‘worrying’ engines to do are turbocharged units like the Integrale 16v not because they are complicated but because they have to go off to be calibrated on a rolling road and the chances of something going wrong there that will terminally damage the engine are about 1 in 2. I don’t like that. It may be something the owner (fitting his own ancillaries) or the dyno shop operator never even thought about like a wiring harness issue or poor design of the exhaust manifold. A turbo unit is a like a reciprocating engine and a gas turbine bolted together – they have nothing in common at all and it take great patience and fantastic skill to do it right. All very alarming to watch from a distance when you know as the engine builder that everything has been done right ‘your end’.
I could certainly indentify the most tiresome stuff as being engines that require special & complicated belt drives for dry-sump/alternator/water pump/supercharger all on the same unit. They really give me a headache and always the client wants ‘how much?’. How do you cost something you’ve never done before?

Q: What was the most powerful engine you`ve ever built? In what car did it work?

A: The bigger the engine the more powerful it can be made. I stick to things with 4 cylinders and about 2liter. I did a lot of different stuff in the years 2005-2010 for Irish Tarmac Rally. I did the gasflowing and head prep on many Vauxhall 16v units that were built up and tested Ireland for National level tarmac rally. The personal best was 285bhp from a 2050cc 16v unit on Jenvey/DTA injection. Not a lot of people can do that and it’s not easy. With the collapse of the Irish economy it’s all gone now and I don’t expect to be doing that again. I did an extremely difficult big valve conversion head (2” diameter inlets) on a narrow-angle Jaguar 6cyl to go in  full-race XK120 for vintage racing which is very big in the UK. I had help from advanced simulation and the porting work in the head was borderline break-thru the ports were so big. And it had huge cams too and massive piston domes because of the need for high compression with that big roomy hemi layout. At each stage the added-value grew and grew and to be honest it was a massive relief when it was finished because until the final checks of valve-valve proximity with the cams in I did not know if it would be possible to complete it successfully until the day before I shipped it to the clients, a well-known specialist. They completed the engine build and in a phone call remarked to me after their dyno-tune session, ‘fuck me we’ve never seen anything like it!’ They had  never seen anything like it and it way was too powerful for the dyno they’d used for years which meant it was well over 315bhp, not bad for a 1950’s design with a bit of GC thrown in. Turned out 327bhp and 320lbf ft on Superflow bench dyno test. I think the bhp figures they’d given me from their units were garbage really. 

Unfortunately despite the most careful coaching by me to them about ‘the racing powerband’ before ever starting work, they complained it had, ‘nothing under 4000rpm’, which it was not supposed to anyway. If you add it on at the top you take away at the bottom, all engines do that. The truth was they needed a different gearset in the gearbox but they never got round to dealing with it. 

Did you note spectacular break-downs or blow-offs?

A: Nah, these are GC engines for chrissakes!

How many engines do you build every year?

A: About 20 engines.

What is the most pleasant moment in building an engine for you? And what is the most fascinating part of your work?

A: The challenge of making a living with your own brain and hands and no-one else to depend on. Actually no-one does this because they like engines, anyone who says that isn’t a race engine builder he’s just a mechanic. They do it because they’re bloody good at it. Your worst enemy is the engine and you can’t let them get the better of you. Call it man against the machine – they’ll take you over if you let them. Can’t have that.

When and how did you establish your engine building company?

A: I had a firm in Kent for the 90s and sold out to work in F1. Then I became a Chief Engineer with Napier Turbochargers for some 4 years which is how I ended up in Lincoln. This completely new firm was formed by me in about 2002 after I resigned from that well-paid job to be a small boy again and play with expensive toys. 
How did I do it? I came home and said to my then Russian wife, ‘I’ve resigned from Napier.’ She said ‘what do you know about race engines..?’

Did you race cars in the past? Where did you participate, what cars have you driven? Any successes? Why have you given it up?

A: I’ve both raced and rallied on a small, clubman scale, enough to know about car prep and what the sport is about. A Lotus twincam MkII Escort and my Fiat-Abarth 124 CSA. To be any good at what I do you have to get that experience or you can’t advise others who depend on to tell them what’s right and wrong. I only did it for experience, had no intention of making it my hobby, far too expensive and destructive. Heartbreaking enough watching others doing it. Money always wins no matter how good your driver or car.

You published “Modifying and Tuning Fiat/Lancia Twin-Cam engines” in 2010 and reprinted it in black and white in 2013. Your books are considered to be “THE” book on Fiat/Lancia DOHC engine tuning. What gave you the idea to write it? And how long did it take to write it?

A: That was my first book published in 1995. I wrote it to get more exposure for the TC engines as a choice for a competition car and to help my firm in Kent. Unfortunately a year later the economic recession Prime Minister John Major hit us and we started losing markets all over the world, especially Canada, USA, Australia and New Zealand. It was terrible really. We went from making a huge amount of money to almost none and I sold out in the end. So I never really was able to capitalise on the success of that book that had taken me a whole year of evenings and weekends to write – whilst running a race engine firm at the same time. By the time I joined Brian Hart I was wrecked. He saved my life really. Before that book, people ‘in the trade’ laughed at Fiat engines. Now they send me Xmas cards.

Your book apart from theoretical knowledge contains many practical tips on engine tuning. Is it all your own experience?

A: Well, be aware the  a new GC book came out last year which I wrote in 3 months and published at the works (printed in Poland!) which shows you how much quicker it is with computers. It’s a similar name but a totally new book called ‘Modifying and Tuning Fiat/Lancia Engines’ – a subtle change of name but a much bigger book in scope and size. A full-color 500 off limited edition actually but there are plans to release it soon as a black & white print too. That book is not just about twincam engines it pretty-well covers the whole spectrum including SOHC, 16v, Gp4, 20v and so on. Is it all my experience? Yeah, 99% of it. With an honors degree in automotive engineering and years of experience of so many things - you’d expect that wouldn’t you.

Who would you recommend your book to? Can anyone succesfully build and tune a Fiat/Lancia DOHC engine with this book in hand?

A: This book is aimed right at YOU dear reader! Yes of course they can – buy the book and see for yourself. That is exactly why and how I wrote it – to encourage enthusiasts and tell them how so we can together ‘protect and survive’ the TC family – the finest production engine ever made. My 3 year old could build a TC engine with that book.  Now – where has my 3 year old gone?!!

Croft is a very big name in the engine world. Do you hope that someone in your family will carry the "engine tuning" torch for you in the future? 

A: Haha! You flatter me! I don’t have any kids, doing engines is bad enough.

Q: One of the biggest advantages of the Lampredi's engine is its availability, relatively low tuning and maintenance costs and great durability, which make it ideal for less wealthy enthusiasts. Are you afraid that rising costs of petrol, legal regulations that are aimed at promoting ecology and "clean" propulsion will eventually turn all petrol engines into pricey extravagant toys available only to the financial elite?

A: Hell no - we only work for the financial elite anyway! The rest use Fords.

What are your thoughts on engine development today? Engines are more torquey, more powerful and keep downsizing. Turbocharging are fashionable. There are many accessories, like start & stop, that were invented a while ago but are making a comeback today repackaged as novelties. Have we reached the peak of petrol based combustion engine development or may there be some revolution waiting for us in the future? Or, to put it more bluntly, can the engines get even better?

A: Reciprocating engines are rubbish. They waste over 70% of the energy. Fortunately we should not worry because global warming has gone way past the tipping point and the planet will melt in 20 years time. By the time anything sensible is developed we’ll all be dead, it’s all been left way too late and watch the space as 60 billion Chinese wake up to the thrill of owning powerful petrol engines, encouraged by watching F1 at the Beijing circuit…

Q: In your book it seems that you favour twin double choke carburettor solutions as the best. Why is that? Is it because of their cost, easy tuning or some other reason that they are better than installing, for example, an electronic racing injection system?

A: One-choke per cylinder is the single most cost effective tuning mod you can do because each cylinder’s pressure waves then act without interference and can really get to work and bump-up the volumetric efficiency and power output. 

A carburetor responds to increased airflow and delivers more gas on its own. Do we really need electronics to do that?
If you are a National level champion sure go fuel injection and then pay another 50% of the cost of the engine for all the hardware and dyno calibration and 10% more power with a bit more driveability. Otherwise you are totally wasting your money even if it is flawlessly calibrated. Either that or you’re suffering from some weird clinical disorder that compels you to tune engines by numbers with a laptop.
Take one of mine on Webers against one of yours on FI and mine will leave yours for dead. Because the money you have wasted on gismos, I will have spent on things that make my engine faster and more reliable. 

Q: What car do you drive daily? Do you own any classic cars?

A: I own an old Range Rover with leather upholstery. Race engine builders rarely drive fast cars. By the end of the day a highly tuned car is the last thing you want to see never mind get into. You just want to get home quietly and safely and get drunk. Mind you I do own a 12m offshore powerboat with 3 of my engines in it as well….

Q: If you had to choose one car you`d have to drive for the rest of your life, what car would it be? Please consider that you would have to buy it and maintain.

A: White half-track 1944 version. I have a track licence from my days in the military, might as well use it. And it’s solid. People drive real bad in Lincoln.