Full race 2.7

[jerrycan]

I'm thinking of building a 2.7 engine to use in a MK1 Triumph 2000 which would be suitable for a bit of Historic Saloon car racing and would welcome some practical advice.

The plans include 77mm pistons (VW 1.4 first oversize, thanks Triumph-V8)  and Maxspeeding H section steel rods.

Questions are is a standard crankshaft OK to 7500 rpm or does it need nitriding or tufftriding?

What is the best camshaft Kent or Newman?

I've read quite a bit about using valve springs that are actually too heavy and cause premature wearing of the valve train, what springs offer the best performance without doing damage to the camshaft etc?

Lightweight flywheel or standard?

Would it be possible to get 200 BHP using Lucas pi?

I'll no doubt ask more questions as I progress.

[JohnD]

The problem is the stroke.

In days of yore, such as the 1931 Tablots, straight six and as vibration-free as any T6, engine designers sought power from stroke, by going for torque.    The biggest Talbots are 3.4L, with a bore similar to a T6, but a stroke of about 150mm.    They provide enormous torque, but cannot be revved beyond about 4.5K, without risking the bearings and rods.   This is because of piston acceleration, as they stop at top and bottom of the bore, but must traverse its length with each revolution.     Modern road and competition cars have gone the other way, short stroke and high revs, to gain power.   For instance, the 2014 Renault F1 engine had a stroke of 53mm and was limited to 15,000rpm, when the mean piston speed was 26.5m/sec, which still needed exotic material and fabrication.

Acceleration is a difficult calculation, and what is usually used instead is mean piston velocity (MPV), much easier.  In half a revolution, the piston must move from one end of the stroke to the other, so MPV = Stroke/ (60/(Revs x 2)).     A result that is over 20 meters/sec indicates that the stresses will be in excess of what normal production materials can sustain.   These tables show the MPV for a T2000 and T2.5, and reveal why the latter cannot be revved beyond 6K without risk.

2L, 76mm stroke

RPM	Mean speed in mm/sec	Mean speed in meters/sec
6000	15200	15.2
7000	17700	17.7
7500	19000	19.0

 

2.5L, 95mm stroke

6000	19000	19.0
6500	20840	20.84

 There is a 'recipe' calculation for actual piston acceleration.   0.000457 x Revs^2 x Stroke in inches x (1 + Stroke/(2 x Conrod length in inches) )   This gives a result in Imperial, but converting to Metric gives:

2L - 19558 m/sec^2

2.5L - 24854 m/sec^2

This acceleration should be compared with 'g', the acceleration that the mass of the Earth exerts on everythong we see around us, at 9.8m/sec^2.      It means that  a T2.5 piston that weighs less than 350gms on the bench, at 6000rpm 'weighs' nearly a metric tonne (882kgs).

So my answer to your question on the crank is no, and it needs more than just tuftriding.    The TR racers who claim more than 250bhp from 2.7L engines use billet-machined steel cranks.  For one of those, you must consult your wallet.

John

Edited July 22, 2018 by JohnD

[Triumph-V8]

I would take the risk!

My TR6 has done more than 20.000 Km and reved up to 7000

where I placed the limiter. Meanwhile I stepped back to 6500

but that is a limit I will touch from time to time. It is just the the

cam with 290 degrees and the EFI that provides Lambda 0.87 all

the way under full load.

 

The crank is billet EN46 and if tuftrided and with pretty much less weight

from piston and rod it will make the job (some time).

 

The VW pistons are not forged but with the smaller rings suitable for high revs.

They might be the limiting factor although I see the 20m/sec limit became a

bit weak during the last years. It is pushed to around 24m/sec.

Anyway we have very short rods and from that very high acceleration of the piston.

That is not nice but there ist not much room to improve. Next urgent  step would be longer

rods and shorter pistons but Maxspeedingrods would do them only if I take three sets. The

result and spent money might not be a perfect relation.

 

So I see the risks as pointed out above but would give it a try but be aware all must be

perfect, its mountain territory. Cam could be Kent 300 degree or a bit beyond.

Race engines are always at the limit, otherwise everybody could do the same........

 

PI can feed that engine but I would calculate some problems due to less manifold

pressure from the cam. Maybe the speed density with the diaphragm must be swapped

to alpha/n like Kastner explained on his pages. The metering is done by a curved disc

that rotates with opening the throttles. Both springs inside the MU must meet the cam

and the envisaged cam is far away from CP cam and will need different springs to be set properly.

Also these cams cause pulsations at various revs that affect metering badly.

It is some try and error, it may be easy to solve but may also require deep modifications.

[JohnD]

Thank you, V8!

Jerry, I think between us we have shown how far from normal reliable you are thinking of going, and the extremes of cost that you will need to cater for.

After that, it's up to you!

Good luck!  John

Edited July 22, 2018 by JohnD

[oldtuckunder]

A few competitors in the Sprint Hill Climb championship have run 2.7 T6's with around that BHP number, but have either run Tripple Webbers or EFI . I suspect because its easier to get the fueling about right, there may not be many people with the expertise to set up a Lucas PI at those limits.

I think 2.7 head gaskets can also be wallet lightening, however I suspect from the spec your aiming at you'll have to do what we all have to at times which is tear up the invoices as they arrive.

I wouldn't take John's comment as don't do it. We all enjoy an interesting project as it develops. 

About my only two cents worth would be with a relatively heavy car think about an engine that will produce as much torque as possible in the 3-5.5K band as that's where you will get the most driving benefit, an engine that's producing 200 bhp at 6.5K sounds good, but I think I'd rather have 150 and an engine with way more torque  in the mid range. Its also cheaper to engineer as you keep out of the areas where things start stretching and flying apart.

NB. +1 for the maxspeeding rods, they happily pull 7K (for brief periods) in my 2ltr.

Alan

[jerrycan]

Thanks for the replies, food for thought. What are you thoughts on valve springs?

I don't want to learn from my own pile of scrap parts and I realise that there is some real life experience on here so I hope you all don't mind me picking brains!

I agree that maybe the Lucas pi is a bridge too far and I may spend the rest of my life trying to get it to fuel right. Maybe I'll just have to bite the bullet on the triple webbers.

Has anybody used 3 SU's with any success?

Triumph-V8 has pointed me in direction of a custom head gasket (thanks for that) and as long as I'm not changing it every weekend it's not going to hurt too much.

I hear what your saying otu I'm not expecting (or wanting) to set the world on fire I just would like to get out there and have some fun so maybe I should lower my sights just slightly and go in the direction you suggest. I certainly want to spend more time driving than with the engine in bits.

[Triumph-V8]

Gasket maybe Elmeso-Reban custom made for about 140 Euros.

They have a website.

 

Springs must suit the cam.

If they make the cam fail they bound what will eat the top of lobe

or will eat the lobe from bad oiling what happens at (long) idle.

To be on the safe side a race engine should not idle much or for a longer time.

The beding in cam and followers is the main process for long life.

Would take the springs recommended for the cam, run cam in with recommended process

for 20 minutes use ZDDP and that is what we can do.

 

A interesting idea might be with hard springs to bed in with soft springs avoiding high revs

ans when engine is ready to use swap the springs to the race springs.

[oldtuckunder]

47 minutes ago, jerrycan said:

What are you thoughts on valve springs?

I hope you all don't mind me picking brains!

 Maybe I'll just have to bite the bullet on the triple webbers.

Has anybody used 3 SU's with any success?

 so maybe I should lower my sights just slightly and go in the direction you suggest. 

The advice I have followed without regret is that Twin Red TR5 springs are just about optimum, however you should also be led by the advice of who supplies your cam, (unless of course you think they are just trying to up sell you).

IF anyone minded brain picking I'd have been thrown off long ago.

Triple CD carbs is a Marmite Question, a good start read could be https://www.tr-register.co.uk/forums/index.php?/topic/43950-are-triple-carbs-rubbish/page-3?hl= triple strombergs

I'd not consider it lowering sights, but maybe rather building an engine for intended use rather than aiming at a number that may deliver the opposite.

NB If your thinking of Historic Saloon Racing check the regs first before building the engine. Nothing worse that spending a lot of time and effort only to be told at scrutineers "you can't run".

NB.  If the regs allow it? EFI would probably be as cheap as triple webbers.

Alan

[socalspitfireguru]

3 hours ago, jerrycan said:

Has anybody used 3 SU's with any success?

This wont work very well without a massive balance pipe between the three.

Triple Webers / Delortos work well because they are effectively six single carbs all working together.

When three SUs or Strombergs are used, the timing of the Induction stroke of the paired cylinders is not 180 degrees apart, so the air flow in double pulses with a long gap between the pairs - this really upsets the way they work.

If you could create a very complex manifold to pair up 1 & 6, 2 & 5 and 3 & 4 then it would work - just like a proper extractor manifold. 

 If you could  make them fit, then six single SUs would work - unfortunately the float chambers stop one from getting them close enough together.  Synchronising them would also be a nightmare.

[Nick Jones]

Not a 2.5 guru but have always understood that revving the 2.5 beyond 6k brought it into the torsional resonance zone resulting in rapid crank failure.  Presumably this can be mitigated by suitable crank dampers (the factory one doesn't count!).

As with the 1500, the smart tuning route is to go for big torque at moderate revs and over as big a rev range as possible.  With suitably chosen gearing this can produce a very rapid car.  My own 2.5 PI (now sold) with EFI made just under 150 bhp with the original "132" cam.  That had some head work, raised CR, and TR6 cast exhaust manifold.  The best feature of the engine was a nearly flat torque curve with > 160 lb/ft from 1800 - 5200 rpm.  Purely a road car, but a fairly rapid one and easy to drive fast as it didn't much care which gear it was in!

Of course 2.5 with claimed power outputs of 180 - 200 rpm are out there but not that many.  Fewer still that turn to 7,500 rpm and those that do are probably very pricey builds with billet cranks.  Of course, there is a big difference between touching 7 - 7.5 k briefly in 1st and second gear and holding it for 20+ seconds in 3rd/4th on those long straights!

Nick

[oldtuckunder]

14 hours ago, socalspitfireguru said:

If you could create a very complex manifold to pair up 1 & 6, 2 & 5 and 3 & 4 then it would work - just like a proper extractor manifold. 

 

Ah you mean this sort of thing!

[yorkshire_spam]

Has anyone ever done 6 mikuni/keihin carbs on a 6 pot? They crop up for sale in 3s quite a lot. I have a set of 4 waiting for a manifold so they can go on my 1500.

[oldtuckunder]

Yes there is a guy in the states that sells a kit for doing it. If I can find the picture or link I'll post.

[oldtuckunder]

Found a picture, but cant find link.

Pretty, but on a hot day that filter set up would be atrocious.

Alan

 

 

[JohnD]

Jeff McNeill, of Totally Triumph.Net in Ca, USA, fitted them to his Mrs.Jones Spitfire, and even with only four, said that balancing them was difficult.

For four Keihins, if there are only three conditions, 3 Bears style, there are 81 different setups, only one of which is all correct.   For six there are 243 (3^6)  so endless fun in the garage.  But of course, the possiblities are (nearly) infinite.

John

[Triumph-V8]

3 hours ago, Nick Jones said:

 Of course, there is a big difference between touching 7 - 7.5 k briefly in 1st and second gear and holding it for 20+ seconds in 3rd/4th on those long straights!

Would agree to that, the TR6 with proper fuelling and balanced well, maybe combined with a light flywheel,

becomes a totally different car even with a relatively mild cam with 290 degrees.

It likes to rev very free and so you touch the 6000 quite often because

it sounds nice and the engine likes that. Its fun......

 

But I would never hold the engine at 6500 on the straight,

the engine would do that but something inside tells me that

it is not good for that engine.

 

Torsions of the crank will be affected not only at the front end by the damper but also

at the rear end what normaly is fixed by the flywheel. If flywheel and

clutch is much lighter it might also have influence on the torsion.

Anyway these special cranks are so expensive that they boost every engine price

and from that it will be a late stage in engine preparation.

 

 

[GT6Steve]

1 hour ago, oldtuckunder said:

Yes there is a guy in the states that sells a kit for doing it. If I can find the picture or link I'll post.

That would be Chris Canicelli at PRIRACE.com.  Or WAS.  Looks like he's lost the URL??

 

[Nick Jones]

59 minutes ago, GT6Steve said:

That would be Chris Canicelli at PRIRACE.com.  Or WAS.  Looks like he's lost the URL??

 

He's changedhis trading name I think ( now MotoCancelli?). Too much negative publicity maybe.

plenty eye candy, eye watering prices, engineering quality and customer service........ bit mixed.

Nick

[Nick Jones]

Doesn't seem to have his own site any more.......

There's this

https://www.exoticautoshops.com/texas/moto-cancelli-dickinson-tx

My advice if wishing to buy his products would be to google him..... then, if still wishing to "invest", don't spend anything you are not willing to write off to experience.....

Nick

[jerrycan]

I'm beginning to have serious second thoughts about this, perhaps just keep it 2.5 with whatever over size the bores need to make good, twin HS6's and a camshaft that will give a nice flat torque curve. It will help the budget no end and probably keep running with just routine maintenance.

It's certainly been good to get info and opinions of people who have 'been there done that'

Thanks guys, don't feel you have to stop if there is anything else I could think about!!

[oldtuckunder]

No in my humble opinion you have now reached the right point, to start working out what you really want from the engine, and how to build it selecting things that will you give the best bang per buck and create an enjoyable reliable engine. Having formerly had to rebuild a broken competition engine 3 years on the trot, i'd say its the small inexpensive things and getting things right (which seems to take a lot of research) that really make the difference.

Again IMHO I'd perhaps take a look at Rally Spec 2.5 engines, as they will probably be far nearer to what you want lots of grunt, rather than high bhp race screamers.

Alan (Now in 3rd year on good engine, but still anal about oil)

  

[jerrycan]

2 hours ago, oldtuckunder said:

No in my humble opinion you have now reached the right point, to start working out what you really want from the engine, and how to build it selecting things that will you give the best bang per buck and create an enjoyable reliable engine. Having formerly had to rebuild a broken competition engine 3 years on the trot, i'd say its the small inexpensive things and getting things right (which seems to take a lot of research) that really make the difference.

Again IMHO I'd perhaps take a look at Rally Spec 2.5 engines, as they will probably be far nearer to what you want lots of grunt, rather than high bhp race screamers.

Alan (Now in 3rd year on good engine, but still anal about oil)

  

I think you've hit the nail on the head!!

Sometimes I just need other people to point out the obvious (so the wife says)

[Triumph-V8]

There are several things that must be taken into account.

If you want to participate in competition you need an engine that

is on a level to compete with others, otherwise its no fun.

 

If the competition has rules it is essential to read them first.

Old Group 2 regulations for example will not allow to swap rods and crank

and also the head must be original.

 

If you aim for power with a limited budget you must do the things that will give

best performance for money.

With no doubt that are single inlet runners for each cylinder and a wilder cam.

The other thing is more displacement, that is the easiest way and keeps low

end torque.

 

It is not advantageous to build a sports engine on the twin carbs because

the things become nasty from a 280 degree cam on.

The PI system offers 15 BHP over the SUs without disadvantages and is a

must on a sporty engines like EFI or Weber DCOE or similar.

 

So do not jump from one extreme to the other and leave mountain territory

and now fiddle on the ground what is boring. Its like drinking: Half full is

wasted money! We had several British machineries that bored out the block to

77mm without additional price. The VW piston is 30 Euro and from that I would

recommend to do that first especially because the stock pistons are already

at the limit.

 

So now good luck and keep us informed about the results!

[TRTOM2498EFI]

I run a very tuned, fast road TR6, and read this thread with interest.

If the engine is assembled well, and very carefully balanced, with a good cooling system and very frequent oil changes, the engines and very robust, smooth and powerful, and will last.

I used a ribbed block from a saloon, and I am on a +40 bore, with AE pistons, late TR6 crank, Carrillo rods, Newman cam, Newman steel followers, lightweight steel flywheel, ARP head bolts, line bored, and has not given me a single issue since it was built in 2011, after X2 Round Britain Reliability Events, X3 10 Country events, trip to Le Mans, Sprints and hill climbs, track days, and driven regularly to 6500+RPM based on an electronic (Stack), accurate tachometer.  40-50k miles. I just run a regular crank damper, and had no issues in the department either.  

Vibration free balanced the below components:

AP Racing Clutch cover.

Lightweight steel Flywheel

Crank pulley

Carrillo rods

Pistons

Camshaft.

https://vibrationfree.co.uk/ 

Not a cheap undertaking, but well worth the effort.

 

Some good advice above, and read with interest !

 

 

Cheers.

 

 

[jerrycan]

Well thanks for all the inputs. So I've had a rethink, due to talking to various people reading the posts on here and looking at the costs involved.

So my current thinking is 

Block line bored and + .060

Steel rods

Newman PH3 cam, steel cam followers and valve springs

Triple HS6 SU Carbs (yes I know!!) If these can't be made to work then PI is a fallback!

Standard flywheel, tuftrided crank and standard damper all balanced at Vibration Free

Undecided about exhaust manifold (It's the cost/benefit thing)

I'm thinking of using a Gripper LSD.

I'm keen on using the oil gallery mods which have been described on various threads on here and using an accumulator. I like the idea of having oil pressure as soon as the ignition is switched on before the engine has turned!

I'm thinking of using a standard but rebuilt o/d gearbox, I have a choice of an A or J type overdrive. Is one better than the other?

By the way this car will be primarily a road car but able to run around (maybe at the back) in the occasional CTCRC Pre 1966 Touring Car round.

Any thoughts are very welcome.