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dream engine - suggestions?


Sam C

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Sorry, yet another big question!:

I would like to begin building up a 'dream engine' for my GT6 and I'm wondering what everyone would suggest as the starting point?

- My instinct would be for 2.5 litre and assume it would be easiest to just buy one from one of the bigger engine triumphs - sound sensible (or is there any advantage to having a GT6 engine stroked?)

- Are there suppliers that sell improved heads and / or inlet manifolds and does anyone have any experience of these? If they're really good would it be more sensible to just replace the head and keep my current 2.0 block?

- What carbs would it make sense to go for?

- Changes to ignition (megajolt for example - fitted one before to a mini and found it very good)?

- In terms of performance: I'd want a solid 125 bhpish and I don't want it too cammy. It's for weekend driving and I want it to be reliable. I also don't want a dangerously over-powered GT6 given that the back end's a bit lively at the best of times!

- I'd expect to use my current GT6 box because It's just been rebuilt.

- I'd want to spend no more than about £1k

I rather imagine there's a curve here so some difference (2.5litre rather than 2.0) will make a lot of difference for not much money, and others will be less 'bang for buck' (I'd guess inlet manifold for example).

Cheers all!

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First bit of advice is to drive a 2.5 engined car, so you decide which you like. It is not simply that the 2.5 is more pwerful, in terms of power not a huge differenc. But the delivery is at much lower RPM with fantastic torque. But not so revvy. Big decision.
125BHP should be simple enough, a 6>3>1 manifold (not cheap though) pair of HS6 carbs, bit of home flowing on the inlet manifold. Good air filters. A mild camshaft, vitesse/GT6 MK2 would be fine, or racier if you fancy. Witor does a hybrid one that looks interesting ;)
A bit of gasflowing on the head may be good, again possible at home, and maybe a skim. Megajolt an excellent idea too. Bung it on a rolling road and you would be happy I shoudl think.
But the budget will go fast! manifold £400? Cam £100 odd with followers, if you get a head done for you.....that would be about there I reckon. But you may have much of what you need already?

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Ok your budget is £1000 .  To start with I should reveal my cards and state that I am not in the "slap a tired 2500 saloon engine in a GT6 and you must have a better car" opinion group - 'cos it's bollocks. Some will swear by it but then they obviously don't like sports cars (cue loads of angry responses!). Stick to 2 litre.

Where you end up will always be a function of where you start of course. What condition is your present engine? This is really important. If your engine is tired I would always advise spending the money on rebuilding the short engine and saving other improvements until you have the money. Too many think it's all about buying the right bits and bolting them on job done. Read KK, Izard, GT etc (check my signature for link to docs).

As best you can I would aim to have a short engine that has been blueprinted to the tolerances. I would also have the deck the block (mandatory) and balance the crank etc. If you have to have the engine machined to this spec, your budget is probably blown - but it's a good place to start.

After that if you are on a budget:

Cylinder head: The experts will quote you a fortune on these but really, a 3 angle valve seat job should see you well on the way to 125bhp though. If you've decked the block you will only need about a 20 thou skim to give you an ideal 10:1 CR. Be very wary of "experts" that sell "Stage II" head etc - there is no standardised definition of what waffle like this means. I onced asked ToiletTune 3 times in writing to give me the specification of their "Stage III" head -  no reply. The salesman when asked face to face had no idea what the CR was! Yet they will want you to part with about twice as much as it would cost to do it yourself.

Exhaust: 6>3>1 is ideal but expensive and the only one available at the moment (Pheonix) is pretty expensive (and not great). OK, GT will do you one but that will break your budget just for the manifold! The best advice for your budget and aspirations is a TR6 standard (6>2>1) manifold. Problem is you will have to fabricate the downtubes to the exhaust. Don't even consider buying one of those aftermarket 6>2>1 manifolds, proof if it was needed that the people who sell this sh*t don't know diddly squat. The exhaust system could be one of the "wheel-barrow" off-the-sheld sh*t that I hate or build your own 2 1/2 inch single system which would not be hard using Jetex parts and much better.

Camshaft: You are on a budget - don't go and spend money on a so called "fast road cam" 'cos that is marketing managers BS. If you are starting with a GT6 engine the standard cam is better on carburetion than many of these so called upgrade cams!

Induction: HS6 with short dashpots and a GT6 manifold which has had some die grinder/dremel action in the form of opening the throats to 1.75 and opening the siamised throats to be equal (pictures on another thread in the last week).

Don't use those silly (and very expensive) K&N pancake filters (too shallow in a GT6) but ideally make an airbox fed to a big (cheap) cone filter.

Remember buying a set of Ping clubs will not make you Tiger Woods. Buying all the bling tuning bits will not make your engine produce HP. It's an accumulative
effect based on where you start.

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Thanks all - this is good stuff, just the sort of thing I needed to know.

Richard, it's a MkIII. The suspension is Spax shocks, with the extension pieces to attach rear shocks effectively to the chassis (rather than inner wheelarch), and it's rotoflex.

Sounds like it's better to stick with the engine I've got, which seems to be really good - sounds lovely and runs well - and concentrate on ignition (megajolt) and inlet and exhaust manifold and SU carbs. Perhaps after then i'll look at a worked head.

Cheers all

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I have approx 120 hp from a very well used standard mk2 Vitesse bottom end, Pheonix 6-3-1 and a lightly worked head with 3 angle valve seats.  CR is standard.  It also has EFI and  mapped ignition.  Not convinced the latter have much effect on ultimate power but they certainly help driveabilty and mpg.  If your Mk3 engine does not have the mk2 cam then that would be a good upgrade.

2.5 changes the character of the car (you may like it - Clives advice to try driving one is good) and also increases the risk of transmission failure.

Nick

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Nick makes a good point about the fact that it is a MK3. If it is a late one (non-rotoflex) then it will have the 2.5l head and domed pistons and the very mild MK1  (18/58) cam. The MK2 (KC/HC engine) cam has a far better profile and would make marked difference -I think the distrutor advance curve will be different too.

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just re-read the first post. Ref "over-cammy" so yes the std GT6 mk2 cam would be a good choice. But that "should" be in there already.
Georges advice is sound (though TR5/6 owners all believe they have sports cars  :P ) in that the engine needs to be in good condition to start.
Indeed, if it is, you may find setting the current one up may be benificial, it is amazing how many people slap new "uprated" stuff on and see a power increase, but mainly because their old stuff was knackered. So megajolt is a good idea to get the timing sorted, and good power can be had with the std strombergs too. The exhaust manifold is important, and I forgot about the TR6 one :B which is pretty good and cheap, but does require that chopping about of downpipe, not too bad if you have a mig.
Other thing to consider for driving experience is suspension, if not already done. Stronger front springs,  decent setup (www.alignmycar.com) and good tyres all make a remarkable difference to the speed you can drive at in the real world. Guess it depends on what you want from the ar though.

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Yep Clive is spot on. It's amazing how much can be done by just refurbing the standard stuff. BTW Kas Kastner achieved amazing stuff on standard carburetion.

It's a MK3 so you have a roto or swing-spring already so your rear-end is not an issue if in good condition. Some uprated shocks would be good. Defo need to chuck the "boulevarde" ride front springs for uprated items and shocks. Don't go overboard for the road. Shocks can be expensive and sh*t quality I'm afraid.

Clive - my 2.5l comments were confined to the GT6, my mate Paul has a TR6 and he's bigger than me!

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ghr630 wrote:
BTW Kas Kastner achieved amazing stuff on standard carburetion.


Indeed he did.  I too am looking at tweaking my engine and have been reading Kastners book Competition Preparation Manual - GT6.  Available via the TSSC shop.

Good read.  The majority of it is OTT for road use as it is mainly written for converting your GT6 to a full race car, but it does have an excellent section on tweaking for the road and tells you what sections of the main book to utilise to improve your car.

Lists how to improve the standard Strombergs 150s. Also states that following considerable dyno testing if you're considering velocity stacks then you need to tailor them to your specific car and not just fit off the shelf ones as it risks losing horsepower.  

Incidentally, he also highly recommends an electric fuel pump and a cylinder block / crank case breather.

Buy the book and you'll read all the info. Only £5.06 plus p&p if you're a member.

http://www.tssc.org.uk/index.php?page=shop.product_details&flypage=shop.flypage_tssc&product_id=2510&category_id=652&manufacturer_id=0&option=com_virtuemart&Itemid=59

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Suspension is good - all either brand new or recently installed - and all uprated (Spax all round with uprated springs on the front). I know people don't like Spax but I have to say I'm very happy with them - just need to protect the adjusters from gunking up!

Carbs are recently re-conditioned by me. I'm confident they're in good shape.

However, the engine does need to be set up. I really want to buy and install whatever I think is necessary before I spend money getting it set up though - sound sensible?

So, my plan know I think is:

(a) install megajolt;
(b) install TR6 exhaust manifold;
(c) install some sort of worked inlet manifold (I'll probably try this myself so if anyone can point me in the direction of any guides that would be great);
(d) decoke head but otherwise leave it 'as is';
(e) stick with Srombergs; and

then get it set up properly (does Club Triumph keep a list of recommended rolling roads for this)?

Sound like a good plan?

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Can't find them anywhere :B
But from memory he used the tr6 cast twin outlet manifold, got a std tr6 twin downpipe and used some bends etc so it turned them through 90degrees so they were in a line front to back (as opposed side to side-you follow ;D) this gets them between the block and chassis rails.
To be honest, I cant see how/why this is better than the oft-slated 6>2>1 manifolds, but then again it was designed by an OEM company, hopefully with some brains/money behind them (that may be very hopeful) as opposed to a tube bending "that'll look good" manufactorer. IMHO ;)

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cliftyhanger wrote:

To be honest, I cant see how/why this is better than the oft-slated 6>2>1 manifolds, but then again it was designed by an OEM company, hopefully with some brains/money behind them


I've thought that as well, I think the TR6 manifold could be viewed as the cheap option.  ;D I recall being told that the World Cup Rally Cars (Saloons) had fabricated 6-2-1; presumably with longer primaries than the cast TR manifold.

Has been said that with a little bit of persuasion (move the block an 1" back), the phoenix 6-3-1 for the TR5 & 6 will fit. This is supposed to be a much better version than the GT6 & Vitesse version.

Oh well the poor relations again....  :'(

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cliftyhanger wrote:
Can't find them anywhere :B
But from memory he used the tr6 cast twin outlet manifold, got a std tr6 twin downpipe and used some bends etc so it turned them through 90degrees so they were in a line front to back (as opposed side to side-you follow ;D) this gets them between the block and chassis rails.
To be honest, I cant see how/why this is better than the oft-slated 6>2>1 manifolds, but then again it was designed by an OEM company, hopefully with some brains/money behind them (that may be very hopeful) as opposed to a tube bending "that'll look good" manufactorer. IMHO ;)




Despite the paucity of funds, Triumphs engineers were actually pretty sharp bunnies and became very good at getting quarts out of the pint pots that BL funding would only stretch too.  
Take the 2.5 litre TR engine, 142BHP with OHV, basic PI, no electronics and two vales per cylinder. Honda's rather gucchi and state of the art K24 2.4 litre gets 160BHP by using Variable  Valve timing and variable inlets along with twin cams, 4 valves per cylinder, multipoint Fuel injection and fully mapped ECU control…

Not bad engineers them blokes in brown dust coats at Canley and just think what could have been if the Sabrina had gone into production… sigh. :B

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380 wrote:


Despite the paucity of funds, Triumphs engineers were actually pretty sharp bunnies and became very good at getting quarts out of the pint pots that BL funding would only stretch too.  
Take the 2.5 litre TR engine, 142BHP with OHV, basic PI, no electronics and two vales per cylinder. Honda's rather gucchi and state of the art K24 2.4 litre gets 160BHP by using Variable  Valve timing and variable inlets along with twin cams, 4 valves per cylinder, multipoint Fuel injection and fully mapped ECU control…

Not bad engineers them blokes in brown dust coats at Canley and just think what could have been if the Sabrina had gone into production… sigh. :B


This is true - up to a point - the oily bits are actually pretty effective and a little semi-modern tech makes them even better.

But then Honda engineers have to contend with considerably more onerous emissions standards; remember the Ferderal spec TR6..... 85 bhp wasn't it..... :'(

Nick

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Nick_Jones wrote:


This is true - up to a point - the oily bits are actually pretty effective and a little semi-modern tech makes them even better.

But then Honda engineers have to contend with considerably more onerous emissions standards; remember the Ferderal spec TR6..... 85 bhp wasn't it..... :'(

Nick






Ah yes, but that's why Honda were able to break into the US market with such success. While everyone else was strangling their engines with emission control crap, EGR valves, air pumps, cats etc, Honda came up with their rather efficient CVCC clean burn design that allowed their small engined cars to produce comparable performance to bigger fed emission standard engines and didn't require all the bells and whistles.  
Ford bought the technology off them as did Chrysler BTW. Mucho embarrassing for Detroit when little 1.5l Civics were running rings around their humongous land tanks and giving twice the fuel economy.

Of course, we all know about that rather clever engine breakthrough of theirs, it's under the bonnet of every Honda Ballade aka Triumph Acclaim. :)


IMO, binning the Triumph relationship with Honda was one of the stupider moves in a long list of stupid moves that BL made. Triumph/Honda made perfect sense, high end, high performance saloon and sports cars was Triumphs market niche, whereas  Rover was 'Auntie' and never really had the image to carry off the Honda tie up.
Hondas model range was a good fit with Triumphs market segment. Civic - Dolomites, Accords - 2000/2500 Saloons, CRX - Spitfire/GT6


The TR6?  The Honda S2000 owes everything to the TR6.

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What George describes earlier is more or less what I have done to my GT6. I must get it to a rolling road though. Now, what exactly do they do at a rolling road? I know they can tinker with needles and timing but how does tuning for fuel consumption translate to data taken off the rear wheels spinning round?

I was reading (on a previous thread here) about a garage run by a lady (and why not) in Koblenz, where the Rhine and Mosel meet, that is a bit of a whizz with the rolling road (she had done a Vitesse). I fancy another trip!!

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don,
the dyno is a very convenient way of tuning the engine simulating normal running conditions,mostly they are for extracting every available hp from the engine but they can by default i suppose be used to make the engine more economical as the engine will be at its optimum when running at or just above the ideal fuel air ratio typically 14.7:1 IIRC.and the driver may not be aware their car is running a rich mixture.you can actually hear when the mixture is perfect for a particular engineunder load as the exhaust note becomes very smooth and just sounds right.

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