Turbo for 2.5 6?

[SpitfireSam]

Hello.

i have a 76 spitfire. I’m bored of the 4 cylinder soundtrack and lack of power.

i have built this engine with a cr increase, a cam, phoenix exhaust and plenty of other stuff to give it some get up and go, but I’m still underwhelmed. Is my engine reliable? Yes. does it give enough power to keep up with traffic and have some fun? Yes. does it give decent fuel economy? Also yes. 
do I want more power anyway at the expense of all of that? Yes.

so at the start of this year I bought a 2.5L 6cyl from a tr6. 
I’ve been planning a build for a while, looking at the gp3 cam and rockers and CR increases which I understand will yield me a decent kick in power, or I could turbo/supercharge it.

ive done reading into supercharging and understand the principles as I am a mechanic by day. I get that supercharger will give a better drive and I get there is more platform for superchargers but a turbo makes more sense. They are better on fuel, and they do make more power/rob less from the engine. 
i understand they have drawbacks with much more heat in the engine bay and turbo lag - which I actually really enjoy, I know I cannot be the only person who enjoys that sudden surge in power, very addicting.

my aim with this car isn’t to race it, but I very much enjoy spirited driving and I want to have something different. 
 

I plan to put this car on emerald k6 full sequential injection and ignition. I’m friends with a world class TIG welder so making an exhaust and inlet manifold is not an issue. 
my questions are these:

how much boost can the stock bottom end take? 
what size turbo should I go for? 
I’ve seen the number 200hp+ thrown around somewhere with a turboed 6, is this feasible while still having a drivable car (this is not a daily driver, I like fun driving and touring)

anything near that 200hp figure I’d be very happy with 

any additional advice about putting a turbo on this is greatly appreciated. 

the engine will be subject to a full rebuild and any machining needed will be done. I do not want to spend thousands on a custom crank, so I want to push this engine within the realms of possibility with the stock crankshaft.

Yes I’ve upgraded weak drive train of my little spitfire with a Subaru r180 diff in the back and an mx5 5speed conversion midway through progress. 
also to keep in mind that this engine will be pushed back into the bulkhead to avoid the power bulge and get a nicer weight distribution 

 

any questions welcome, thank you for reading  

Sam

[zetecspit]

I know a few NA 2.5 engines out there are running close to 200bhp. How close probably varies depending on who/how it is measured.

But those are well built engines, running triple webers or EFI. I think there is a supercharged TR6 somewhere too? I don't know of any running a turbo, but there may be one or more.

Will a Triumph 6 cylinder work well with forced induction? Probably not as they do have their limitations. If you want big power then a modern engine swap may be a better choice, though there are not many 6 cylinders around. I have an ST170 engine in my spit, behaves well and will respond well to forced induction, as do MX5 engines. Many others too. 

Just my 2p worth.

[JohnD]

Sam,

In your research did you find Peter Cobbold?   He has a supercharged TR6, which he writes about on the TRR message board, and on his website  http://supertrarged.wordpress.com/

In my own search for more power from a 6, I did speak to Kas Kastner, who claimed 200bhp from unblown 6s, but by then it was fifty years afterwards and he said he couldn't remember how.    Is 170bhp anywhere near what you would want, as that's where I am with my present race engine?

John 

[SpitfireSam]

11 hours ago, zetecspit said:

I know a few NA 2.5 engines out there are running close to 200bhp. How close probably varies depending on who/how it is measured.

But those are well built engines, running triple webers or EFI. I think there is a supercharged TR6 somewhere too? I don't know of any running a turbo, but there may be one or more.

Will a Triumph 6 cylinder work well with forced induction? Probably not as they do have their limitations. If you want big power then a modern engine swap may be a better choice, though there are not many 6 cylinders around. I have an ST170 engine in my spit, behaves well and will respond well to forced induction, as do MX5 engines. Many others too. 

Just my 2p worth.

It makes more sense to put in a Morden engine like a 1.8 BAM or indeed a zetec but half of the reason Im doing the 6 is for the glorious sound of 6 cylinders. Also I like to challenge myself with making it work. Do they work well with forced induction? Probably not, they aren’t revvy engines but with some tweaks I can definitely improve it.

9 hours ago, JohnD said:

Sam,

In your research did you find Peter Cobbold?   He has a supercharged TR6, which he writes about on the TRR message board, and on his website  http://supertrarged.wordpress.com/

In my own search for more power from a 6, I did speak to Kas Kastner, who claimed 200bhp from unblown 6s, but by then it was fifty years afterwards and he said he couldn't remember how.    Is 170bhp anywhere near what you would want, as that's where I am with my present race engine?

John 

Yes I’ve had a look at his page and that has some very useful information which I’ve taken note of.

the magic number of ‘200hp’ doesnt bother me as I’m well aware one rolling road may show massive variation from another. But, yes I’d be very happy to make 170hp. I spoke to someone at Goodparts and they said with a gp3 cam roller rockers and the harmonic balancer, I should get near to 150-170 depending on the rolling road. 
but I have built NA engines before, I get what makes them better but I do want to try something new as I’ve never built a turbo. I have seen about Kas Kastners build and I think I saw a very old picture of his engine bay. I’ve not managed to find information about the actual limits of the engine components, can the crankshaft take the punishment of extra power? What about the pistons and rods? 
 

thank you gentlemen for your replies!

[Nick Jones]

There have been discussions on here about this before. Here’s one from more than 10 years ago.

Some thoughts.

A Spitfire is a small, light and fairly flimsy car. It doesn’t need 200bhp plus to be a very brisk road car.

Putting the heavy 2.5 6-pot in a Spitfire fundamentally changes its nature. You gain the grunt and the sound-track, but loose the sharp turn-in and agility. Moving the engine back can mitigate this, but is a lot of work and I think you’d struggle to do it with the long MX5 ‘box. If you’ve never driven a 6 pot Spit or even a GT6, you might want to try one? If you have driven one and you’re happy, crack on.

You’ve already spotted the major issue of transmission weakness. Very interested to see your take on the MX5 ‘box conversion!  Presumably you also plan to do something about the front brakes at least and rear suspension is to be converted to something roto-based?

As for forced induction, I discussed this with an expert a few years ago. It was a short discussion as his advice was to start with an engine with a decent margin of basic robustness. In his opinion even the 2L 6, which is actually a pretty strong engine, wasn’t worthy. To be fair, as a drag-racer Dennis was probably assuming I was aiming higher than I was.

There are quite few road-going 2.5s out there with a reliable, normally aspirated 160 - 180 bhp. This will be enough for a very quick Spit. To get more than this reliably it starts to get expensive (forged pistons, decent rods, carefully prepared rotating assembly, really well prepared head etc) and this will apply whether naturally aspirated or forced induction, though forced induction has the potential advantage of not needing high revs to make good power.

There are also 2.5s out there with over 200bhp. Mostly very high-revving, high-bucks engines in race cars and mostly NA. There are tales on here and elsewhere of forced induction (mostly supercharged) 2.5s over 200bhp, usually short-lived.

I reckon that provided you accept a limitation of 200bhp absolute max, you could build a reliable 2.5 turbo without having spend an absolute fortune on the engine itself. Modern turbos, modern engine management and boost controllers should give the control accuracy to run close to the edge without falling off it. Packaging and heat management will be a challenge…… But I still don’t think you need 200bhp + for an exciting Spit 

 

[RedRooster]

^^wot he says. 

My Sprite putting out 115bhp would see the GT off through the bends no bother, but the GT is a different car altogether, understeering bugger that it is, but I like them both for what they are and drive them to suit 

[SpitfireSam]

9 hours ago, Nick Jones said:

There have been discussions on here about this before. Here’s one from more than 10 years ago.

Some thoughts.

A Spitfire is a small, light and fairly flimsy car. It doesn’t need 200bhp plus to be a very brisk road car.

Putting the heavy 2.5 6-pot in a Spitfire fundamentally changes its nature. You gain the grunt and the sound-track, but loose the sharp turn-in and agility. Moving the engine back can mitigate this, but is a lot of work and I think you’d struggle to do it with the long MX5 ‘box. If you’ve never driven a 6 pot Spit or even a GT6, you might want to try one? If you have driven one and you’re happy, crack on.

You’ve already spotted the major issue of transmission weakness. Very interested to see your take on the MX5 ‘box conversion!  Presumably you also plan to do something about the front brakes at least and rear suspension is to be converted to something roto-based?

As for forced induction, I discussed this with an expert a few years ago. It was a short discussion as his advice was to start with an engine with a decent margin of basic robustness. In his opinion even the 2L 6, which is actually a pretty strong engine, wasn’t worthy. To be fair, as a drag-racer Dennis was probably assuming I was aiming higher than I was.

There are quite few road-going 2.5s out there with a reliable, normally aspirated 160 - 180 bhp. This will be enough for a very quick Spit. To get more than this reliably it starts to get expensive (forged pistons, decent rods, carefully prepared rotating assembly, really well prepared head etc) and this will apply whether naturally aspirated or forced induction, though forced induction has the potential advantage of not needing high revs to make good power.

There are also 2.5s out there with over 200bhp. Mostly very high-revving, high-bucks engines in race cars and mostly NA. There are tales on here and elsewhere of forced induction (mostly supercharged) 2.5s over 200bhp, usually short-lived.

I reckon that provided you accept a limitation of 200bhp absolute max, you could build a reliable 2.5 turbo without having spend an absolute fortune on the engine itself. Modern turbos, modern engine management and boost controllers should give the control accuracy to run close to the edge without falling off it. Packaging and heat management will be a challenge…… But I still don’t think you need 200bhp + for an exciting Spit 

 

Hi nick, thank you for your reply I’ve read a LOT of your posts on here and your knowledge is invaluable so thank you for your contributions.

 

Firstly I do think I’ll struggle to get the mx5 box and tr6 engine in, but I’m not opposed to cutting up my frame or body where necessary as I’m pretty handy with a welder.

 

I must admit I’ve never driven a spit 6 or a gt6, only ever spitfire and a stag of the triumph range but for my job I have driven a lot of different cars I understand the engine is heavier but I believe with it lower and further back it should, like you said, mitigate the negatives.

 

As for the mx5 box conversion. I’m planning to make a YouTube video at some point about my attempt to cram one in, it involves modifying the flywheel, bellhousing, making a different engine back plate, massaging the frame and moving the gear stick forward. 

I’ve modified the gt6 (lighter) flywheel to take an mx5 ring gear as to use the original starter and triumph flywheel and clutch. I’ve made an engine backing plate by scanning and laser cutting to fit the bellhousing bolts. I am yet to cut the gearbox up but I’ve got a plan. The gearbox will first mate up to a standard 1500 engine but when I throw this lump in I’ll have to further modify everything. 

 

As for engine robustness I am aware that all of triumphs line up consist of pretty weak engines but I’m not chasing 200hp, I just want to see what it can do. I ask about 200hp to see at what point do engine components become *too* stressed.

NA engines are great, drive better, probably more reliable and make more sense. But that’s been done, and I’ve done it before so for this I want to try something different.

 

Heat management will be a fun thing to do, not sure how I’ll over come that, my bonnet already has the ‘le mans’ side vents though how much heat they actually allow out is unknown to me. I think it will be a case of making heatshields and heat wrapping where I can. 

I’m planning to put the ECU and associated wiring in my battery box (my battery is in the boot already) 

 

I’m aware that all this is a lot of work, if I wanted to be sensible I’d buy a tvr, but I reckon this will be more satisfying when it’s done.

 

Nick, question for you about headwork. I did read a write up of yours on how you modified a head, I can’t remember exactly what engine, though I think it was a tr6.

What can I do to aid flow, I know the position in which the valve seats were cast in and taking the edges off underneath the seats but is there anything I can do to the throat to aid flow? 

 

Does anyone body know what the breaking point of Internal components is? What psi can the pistons take? How much power before the rods give in? Also any recommendations on cams for forced induction? 

 

Thanks guys! 

[JohnD]

Sam,

On fitting a different gearbox, although you have chosen an MX5 and I chose a Ford T9, have you seen my post about fitting one of those?  https://sideways-technologies.co.uk/forums/index.php?/topic/9855-fitting-the-ford-t9-gearbox/

On heat management, I fear that the original "Le Mans" vents in the bonnet sides are mainly ornamental.   They may allow hot air out, but cannot be described as 'extractors'.   What is needed is a duct, that shallows to zero depth at the rear, with a small lip in the front of the opening.    This lip generates a vortex which penetrates the opening and energises the relatively still air there, drawing it out.    Below is a test that I did with wool tufts and an airgun.  You can see how with the duct, even with no lip, the flow is outwards, not just along the panel.

 

On headwork, I have found Dave Vizard's work to be inspiring, especially his "Theory and Practice of of Cylinder Head Modification", but so have many others!   Copies sell on Amazon for £100 or  more!    Fortunately, his  more specific work, "Tuning Triumphs over 1300cc" is available online as a PDF at   http://auskellian.com/paul/links_files/David Vizard-Tuning Standard Triumph.pdf  See Chapter 6, "Modifying the later 2000 and 2500cc heads" which duplicates the advice in his greater work.

On the con rods, consider the piston acceleration, which can rise to many hundreds of G, making them apparently massive.    The actual G value is a difficult calculation, so usually the Mean Piston Velocity (MPV) is used, and with normal designs and materials a limit of 20metres/second is considered the maximum for reliable life.   The MPVs for various Triumph models are:

GT6/Vitesse	1998cc		2.5	2498		TR7	1998cc
Stroke	76			95		Stroke	78
Revs	MPV		Revs	MPV		Revs	MPV
2000	5		2000	6		2000	5.2
3000	8		3000	10		3000	7.8
4000	10		4000	13		4000	10.4
5000	13		5000	16		5000	13
6000	15		6000	19		6000	15.6
7000	18		7000	22		7000	18.2
8000	20		8000	25		8000	20.8

This shows how the stroking to achieve extra capacity in the 2.5L engine brings down the 20m/s limit to well within the rev capacity of the engine.  Few would dare to rev their GT6 to 8K, but only 6K is on the limit for the 2.5.      I use Maxpeedingrod conrods, but still try not to  exceed 6K for long!

John

Edited December 12, 2024 by JohnD

[hoffman900]

Over 220hp is obtainable from a proper TR4 engine in race trim. A proper, modern developed vintage race 2.5L i6 should be close to 250bhp (on race gas)… all naturally aspirated. 
 

As for what the bottom end can take, it just depends. 

[hoffman900]

3 hours ago, JohnD said:

Sam,

On fitting a different gearbox, although you have chosen an MX5 and I chose a Ford T9, have you seen my post about fitting one of those?  https://sideways-technologies.co.uk/forums/index.php?/topic/9855-fitting-the-ford-t9-gearbox/

On heat management, I fear that the original "Le Mans" vents in the bonnet sides are mainly ornamental.   They may allow hot air out, but cannot be described as 'extractors'.   What is needed is a duct, that shallows to zero depth at the rear, with a small lip in the front of the opening.    This lip generates a vortex which penetrates the opening and energises the relatively still air there, drawing it out.    Below is a test that I did with wool tufts and an airgun.  You can see how with the duct, even with no lip, the flow is outwards, not just along the panel.

 

On headwork, I have found Dave Vizard's work to be inspiring, especially his "Theory and Practice of of Cylinder Head Modification", but so have many others!   Copies sell on Amazon for £100 or  more!    Fortunately, his  more specific work, "Tuning Triumphs over 1300cc" is available online as a PDF at   http://auskellian.com/paul/links_files/David Vizard-Tuning Standard Triumph.pdf  See Chapter 6, "Modifying the later 2000 and 2500cc heads" which duplicates the advice in his greater work.

On the con rods, consider the piston acceleration, which can rise to many hundreds of G, making them apparently massive.    The actual G value is a difficult calculation, so usually the Mean Piston Velocity (MPV) is used, and with normal designs and materials a limit of 20metres/second is considered the maximum for reliable life.   The MPVs for various Triumph models are:

GT6/Vitesse	1998cc		2.5	2498		TR7	1998cc
Stroke	76			95		Stroke	78
Revs	MPV		Revs	MPV		Revs	MPV
2000	5		2000	6		2000	5.2
3000	8		3000	10		3000	7.8
4000	10		4000	13		4000	10.4
5000	13		5000	16		5000	13
6000	15		6000	19		6000	15.6
7000	18		7000	22		7000	18.2
8000	20		8000	25		8000	20.8

This shows how the stroking to achieve extra capacity in the 2.5L engine brings down the 20m/s limit to well within the rev capacity of the engine.  Few would dare to rev their GT6 to 8K, but only 6K is on the limit for the 2.5.      I use Maxpeedingrod conrods, but still try not to  exceed 6K for long!

John

There is more to it than G’s. OEMs and and pro / really top flight amatuer teams use in-situ cylinder pressure sensors and are looking at peak cylinder pressure and its location relative to rod angle, and that is ultimatey what kills bottom ends. 
 

Having had some dealings with Vizard, I am not a fan and think he’s full of hot air. That book will get you started however, but most people doing Triumph heads are leaving a ton of power on the table… copying Kastner (who I personally knew, great guy but limited by technology / knowledge at the time), Vizard who is a decent starting point but that’s about it, and a bunch of “guru” Triumph types who don’t have experience in really competitive racing series. A professional cylinder head professional who works on top flight drag race, circle track, and road race (V8) stuff will find 10-20% more power in the heads than most of the above. I’ve personally been involved in a few projects from Triumphs to Alfas where that has played out…. 10-15% more power in their first attempt over some guru’s 30-40 years attempts at it. 

[JohnD]

17 hours ago, hoffman900 said:

Over 220hp is obtainable from a proper TR4 engine in race trim. A proper, modern developed vintage race 2.5L i6 should be close to 250bhp (on race gas)… all naturally aspirated. 

On your dynamometer!

[Escadrille Ecosse]

Would echo Nick's comments above.

I have built a lightweight (all GRP body) Spitfire, first with a 2L and then 2.5L six. Mine 'only' about 130-140 bhp, but with shedloads of torque. Did pretty well with it in sprints, hillclimbs but honestly it made a much better road car/grand tourer than a race machine. Effortless driving and a lovely noise from the straight six. But the weight of that engine very much makes itself felt.

Personally I think the 2L is the better engine.

I have also built and raced a very lightweight 1300 Spitfire. Roughly 125 bhp (see John D's comments on dynos) but with a 600kg body and 3.55 diff it was an entirely different car. Very, very 'perky' and nimble indeed.

I thoroughly enjoy both cars but they are very different beasts.

Worth having a drive in a 6 if you haven't done so. Suspension tuning will make a huge difference to the handling compared to a standard car but you can't eliminate the effect of all that weight up front.

[hoffman900]

5 hours ago, JohnD said:

On your dynamometer!

100hp/L+ is very realistic on very good race engines on 110 octane leaded race fuel in the States on multiple dynos. 
 

[hoffman900]

Since I can’t edit posts, 100hp/L is what it takes to be competitive / front running here in the States in vintage racing, which have more liberal rules than Europe vintage racing. 
 

12.5-13:1 geometric compression, lobe profiles designed in the last 20 years that that take advantage of the entire lifter diameter with peak valve lifts of over 0.600in (yes even with flat tappets) oh these Triumph and A Series engines, headers designed on 1D computer sims (I use EngMod4t) and top flight pro fabrictors making them, cylinder heads / manifolds developed by professionals with race winning histories on flowbenches that can flow 36in H2O +, lots of dyno time, etc. 

So while dyno’s vary somewhat, they’re all within 5% or so. 
 

This isn’t hyperbole either. Been involved and still involved in this stuff. 

[hoffman900]

Here is a GT6 head from a porter I usually refer people to here in the States (Jason Anderson of Janderson Heads)… 80 grit in the ports but you can see he leaves the manifold roughed up to help atomize fuel. 

[Nick Jones]

Nice looking head 

12 hours ago, JohnD said:

On your dynamometer

It’s only 100 bhp/l. That’s even possible (and then some) from the 6 port A-series.  Triumph 2.5 is a bigger challenge in some ways though as the basic engine design has been stretched to the max capacity-wise. Valve sizes, stroke, “rubber” crank, cooling system limitations all have to be worked around.

In theory, forced induction should ease several of these limitations as you don’t need the revs so much to make power. 

Pistons would be the first limitation of the standard bottom end, then rods, then crank. Head gasket and keeping it cool is in the mix. 

[hoffman900]

5 minutes ago, Nick Jones said:

Nice looking head 

It’s only 100 bhp/l. That’s even possible (and then some) from the 6 port A-series.  Triumph 2.5 is a bigger challenge in some ways though as the basic engine design has been stretched to the max capacity-wise. Valve sizes, stroke, “rubber” crank, cooling system limitations all have to be worked around.

In theory, forced induction should ease several of these limitations as you don’t need the revs so much to make power. 

Pistons would be the first limitation of the standard bottom end, then rods, then crank. Head gasket and keeping it cool is in the mix. 

145bhp is obtainable on a 1320cc A-Series with SU carburetors. I know of a naturally aspirated one with fuel injection, 1320cc, that makes 165bhp. 
 

I know 3 current cylinder head porters that are over 160cfm at max lift (0.600in) at 28in H2O, with a 1.48in intake valve. With their cam packages, they’re up 10-12% of Swiftunes best stuff. 
 

The smaller motors 110-115hp/L (sub 2L) is in the ballpark for a front running vintage race engine. The bigger motors like a 2.5L I6, 4.2L Jags and the like are are closer to 100hp/L. Just frictional losses, less efficient, less favorable bore to intake valve sizes, etc. 

[Nick Jones]

On 12/12/2024 at 5:45 AM, SpitfireSam said:

Does anyone body know what the breaking point of Internal components is? What psi can the pistons take? How much power before the rods give in?

There’s not a lot of data out there on this for forced induction Triumphs as few have taken this approach, or for the 4 cylinder engines either - meaning you are among the pioneers…...

Other thing to bear in mind is that it’s generally unintended events that kill engines - detonation due to going over the (very slim) margin left due to high ambient temps, less good fuel, boost spikes, holding full throttle that bit too long, missing a gear.

Modern tech (especially if you can get knock sensors to work properly) gives the opportunity to manage these things a bit better. Trick is finding the edge without crossing it and breaking stuff…. 
 

Having induction and exhaust on the same side and having to share the limited space with the steering column is unhelpful.., 

[666]

Hoping its not proprietary if not what sort of flows does that head make and what size valves are used used?

[hoffman900]

7 hours ago, 666 said:

Hoping its not proprietary if not what sort of flows does that head make and what size valves are used used?

Not sure on valve size, he’s got them flowing over 160cfm @ 0.600” (28in H2O) with the (Weber) manifold attached. 
 

Here is from another GT6 head from a few years ago. 28in H2O. Red is Jason’s work blue is another head porter’s. 
 

 

He’s done a bit more development since then for customers, so it’ll be a little better. This should be enough to support 220bhp+ from a 2L GT6 engine. 

[hoffman900]

The thing is, and this is something we have seen on another application, but heads developed on a flowbench that only flows 10in H2O may never see that port stall, it just isn’t pulling hard enough, so the conversions people do are inaccurate. Put them on a bench and crank it up, and you will see a port like that fall apart… flow drops, they’re noisy, etc. This is partly why these engines don’t perform as well as the 10in flowbench may indicate. Remember, a running engine is going to see near 100in depression peak, so getting a port quiet and stable, and not falling off at 28-36in is going to make for a way better / powerful engine in the car. 

 

[hoffman900]

I should also add, this is a fixed depression bench. The Superflows and PTS’s are that and are calibrated with Superflow calibration holes. 
 

A lot of homemade benches (Vizard’s plans, Peter Burgess, etc) are floating depression benches. They don’t scale the same at lower vs higher lifts and aren’t that comparable between the two, and tbh, I don’t really trust the floating depression benchss all that much. The fixed depression benches seem to correlate better. 

[SpitfireSam]

Right thank you for your replies chaps! 
 

hoffman900, that head looks fantastic, particularly a fan of the tapped holes to secure the inlet on properly without the silly ‘wing washer’ things - I’ll be copying that. I’ll have a good look at the head and see what power I can release.

Escadrille Ecosse, I’ll see if I can get one booked in at work and have a drive as I don’t know anyone with a 6, well not one that runs anyway. I am optimistic that moving my engine back should help some of the extra weight. 
 

JohnD, I’ve checked out your write up in the t9 boxes and it confirms that there is always more to these jobs than you’d expect. The reason I’m going for the Mazda box over the t9 is mainly price, Mazda boxes are incredibly cheap, got mine from a running car for £40, and when it breaks I’ll just get another one and swap modified parts over, also the mx5 box has a lovely shifting feel, nice and direct. 
I’ve also heard the t9 box has a 1st gear that’s too short? Can you confirm for curiosity? 
and as for the side vents I’ll do exactly what you said and try to fab up some ducting to help draw that air out.

Nick, using JohnDs information and common sense I’ll set myself a rev limit of 6000 and due to the turbo, the power band should be well before then which I hope will in fact help alleviate some stress on the internals. 
I am eager to utilise a knock sensor to get my engine running reliably and smoothly. Thank you for listing the components in terms of weakness, it seems the crank -being such a fat lump of metal- can take some punishment before it gives up, it sounds like it should take what I’ll throw at it.

as for the space to for the turbo, I have approached this issue briefly before when considering turbocharging my 1500, it basically will have to be really low and far back to avoid the suspension tower and the steering column, but my welder and I will fabricate the manifolds so we should be able to work something out - though post turbo exhaust routing will be interesting with the engine moved back. 
if you cannot tell, I’m a big fan of crossing bridges when the come, I seem to work best this way.

Thank you all for your replies they are really appreciated and have given me much to consider, if anyone can think of anything extra I should be doing to release some power while prepping for a turbo or any other advice please so let me know,

cheers!

Sam

[Nick Jones]

52 minutes ago, SpitfireSam said:

it seems the crank -being such a fat lump of metal- can take some punishment before it gives up

Biggest issues with the crank are torsional harmonics/ vibrations and fatigue this because, unlike the 2L there’s no overlap between main and big bearings so it’s less rigid. They do break. Usually through the web between the rear main and #6 big end. 
 

Avoid by

-crack testing the crank paying particular attention to the fillet radii next to the webs, which is where they start. 

-Very careful grinding of the fillet radii on the journals.

- 6000rpm rev limit (some will contest!)

- Use the best crank damper you can find. Aftermarket specials exist but $$$$$!

[JohnD]

Sam,

My thinking on a replacement gearbox was your opposite - I didn't want the labour of replacing it very often, and as I had broken two rebuilt Triumph boxes, the V6 T9fit for 200bhp, seemed the way to go.   But each to their own!

I'll be glad to test any original crank damper/pulley you may wish to use.   It's clear from my own research that the outward appearance of the rubber in one is no guide to its function as a damper.  

As Nick says, there are two other types of damper available, the fluid damper where its viscous oil, not rubber, that provides the damping, and the "Rattler" or pendulum damper:  

 Both are costly!

On cramming turbos in to engine bays where they aren't supposed to go, have you watched the Project Binky videos at Bad Obsession?   There's nearly forty of them, over ten years, as it was a very tight fit!     https://www.youtube.com/watch?v=7hCPODjJO7s&list=PLGSOZAHg1yQHU1tc_3Y5MTQg1qjtxA_nq

John