Triple Webers or PI?

[Madmal]

Good evening, from a new TR Register member!

 

Just purchased my "new" 1971 TR6, having spent an age trying to find one for the right budget and condition. Finally settled on a body off restoration from 9 years ago that needs a bit of TLC to bring it back to scratch. The forum has been superb in providing a wealth of information, some of which answered questions I didn't even ask...

 

So my TR6 has had the SU carb conversion. I'm thinking of either converting back to the original PI system (which I can source at a cost) or fitting triple webers which look fantastic but appear to have a few issues, if some of my research is correct.

 

Does anyone have any experience of fitting triple carbs that they could share?

 

Thanks

 

Mal

 

 

[TriumphV8]

I did all the swaps, driving twin Strombergs, Twin SUs

and the PI in CP version and Weber 40 DCOE.

 

For a friend I did the twin downdraught Webers that

I would not recommend because they make no sense.

 

A friend did the three SUs and was quite happy with them,

it was an easy swap and a lot can be kept as with the twin SUs

but the direct swap to EFI two years ago gained a significant

power increase. He had the SU HIF44.

 

Actually I do the EFI on CP system with ignition control

what seems to be the best conversion to me but needs some skill.

As I am familiar with it its the cheapest, best and easiest way to get

a high performance engine that makes no trouble.

 

The twin SUs are not bad, I would stay with them and try them out.

Individual runners like PI, EFI or DCOE give around 15HP increase

if set properly and a better idle with wilder cams.

Is that worth the effort to you?

 

If you say Yes be aware that all solutions do not work right out of the box

but all three can be made to feed a nice running engine.without bigger differences.

 

The PI needs some attention to establish a proper fuel supply

especially in summer.

 

The DCOE need some additional parts as there are jets to do

the setup or somebody who does the setup what rises the costs.

 

EFI needs the most skill to produce some individual parts but

later provides the easiest way to do the setup.

 

For the swap to PI the cylinder head with the wider inlet spacing

is necessary, the DCOE or three SU manifolds can be obtained

in both narrow and wide port version.

 

Hope this helps to make a decision!

[Nigel Triumph]

Conventional wisdom is that a well set up PI system will give better low end torque than triple side-draught Webers, especially with a longish duration cam as fitted to CP series engines. It's said that with long duration cams Webers are more liable to spit back and give a rough tickover. At the top end, there shouldn't be much to chose.

 

I'm a fan of Lucas PI but must admit I've never done a back to back comparison with triple Webers.

 

 

Nigel

[marki]

Hi Mal.

PM sent.

Mark.

[Peter Cobbold]

Hi Mal, welcome to the forum.

A year or so back I'd have suggested looking into the Moss supercharger kit, but they appear to be NLA.

I would get to know the car first, see if the SUs deliver the torque you need for your driving style. If you rarely run the engine at over say 4000rpm then the SUs will work fine and could even be 'smoother' than the alternatives you suggest. The cost of the change to PI or Webers might be more effectively spent on a cam and gas-flowed head.

Peter

Edited December 12, 2016 by Peter Cobbold

[Madmal]

Thanks for such a rapid response.

 

I am favouring the PI conversion, although I will have to install a high pressure fuel return line from the engine to the tank, but the tank is original so at least it has the necessary connections.

 

Is there anything else I should be aware of regarding a PI retrofit?

 

Mal

[Peter Cobbold]

Mal, Don't forget the disy pedestal, that might be tricky to find. Peter

[Steves_TR6]

Hi Mal

 

Welcome to the forum!

 

Was your car originally PI?

Ie was it a uk car and not a reimport?

 

If it was PI then reinstating PI would be my favourite option, the PI when set up properly is reliable and adds so much character.

 

Whereabouts are you, maybe meet some local members and compare cars/options?

 

Steve

[TR NIALL]

Hi Mal and Welcome to the Forum,if you fill in some of your Profile Details you might find out you have TR Neighbours.

[Tom Fremont]

Hi Mal,

 

One of my '250s has been on triple DCOEs since 1994 and has done 115,000+ miles on them since the last engine rebuild, set up seat-of-the-pants by me. I couldn't be happier. It has the P.I. cam, Racetorations head and exhaust manifold. It is faster in the 1/4 mile than the stock TR5 by at least 1/2 second with me driving ( total amateur ). Plugs are clean and get changed after 30,000 miles whether they need it or not. Rear end is totally soot-free. Fuel economy is 24 mpg IMP overall, 31-32 highway only ( it has O/D ). It will idle at 550 rpm if I want it to ( see video below ).

 

I've been in (2) Racetorations prepared TR5s with triple Webers and one P.I. TR6. The Webered cars gave everything anyone could ask for performance-wise; very strong throughout the range. Purred like kittens at idle too. The P.I. car burbled and farted on overrun but otherwise was fine.

 

My carbs haven't been adjusted in over 15 years. With their ball-bearing mounted throttle-shafts, brass floats and exquisite precision they are hands down the most reliable component of the entire car. Note they were well used when I got them, '60s vintage ( 3 generations before the Spanish version of today ).

 

 

Here in the 'States TRs with the LUCAS P.I. are very rare. The few I've encountered don't seem to have pleased their owners much; they usually come up for sale not long after their restorations. The main issue I'd have with the P.I. system is it gives more fuel at higher altitudes, the opposite of what is needed. Hence they foul and run like !@#$ according to reports from those who've taken them over the Swiss Alps. My '250 ran like a Swiss watch on its Webers at 11,150 ft in the Rocky Mountains - they're self-adjusting for altitude, evidently.

 

In the UK you have numerous rolling roads with Weber experience. You can get them set up any number of places. At IWE in 2012 the TR Enterprises guys told me " We put them on everything we do! " Spoiled for choice, I'd say.

 

Cheers,

Tom

 

 

 

 

A US TR5 idling.MOV

[cp25616]

Lucas Pi all day long, no brainer really.

Alan G

[astontr6]

Hi Mal,

 

I have to agree with the points that Tom made! Altitude is a real problem for the standard PI metering unit, as a number of our Group found out on their Swiss Trip All 6 cars suffered plug trouble.

.But, in my view before deciding which way to go. What is the condition of your engine, regarding compression and inlet manifold vacuum, etc.? These are key points for the Lucas PI system to work properly. Do you know why that owner went over to Carbs?

 

Bruce.

[foster461]

As much as I like the DCOE's if I had a UK car that was originally PI I would do whatever I needed to to put it back to that configuration. It is such a unique part of the TR6 character.

 

If the car was a USA re-pat the DCOE's look great and perform well and also suit the character of the car.

 

Stan

[Tom Fremont]

As much as I like the DCOE's if I had a UK car that was originally PI I would do whatever I needed to to put it back to that configuration. It is such a unique part of the TR6 character.

 

If the car was a USA re-pat the DCOE's look great and perform well and also suit the character of the car.

 

Stan

I agree with this - should have included it in my post. As it is, I've got one I can thrash with reckless abandon and another so over restored that it makes me nervous to drive it more than 20 minutes or so. So I'd need one of the former ( with DCOEs ) to offset the insecurities the P.I. car might give me. No doubt exists in my mind which to take X-country...

 

 

Cheers,

Tom

[foster461]

I agree with this - should have included it in my post. As it is, I've got one I can thrash with reckless abandon and another so over restored that it makes me nervous to drive it more than 20 minutes or so. So I'd need one of the former ( with DCOEs ) to offset the insecurities the P.I. car might give me. No doubt exists in my mind which to take X-country...

 

 

Cheers,

Tom

 

As long as you carry a spare injector, a bag of frozen peas and stay away from mountains the PI is very dependable.

[Peter Cobbold]

 

the PI is very dependable.

That's what I found over ca 180k daily driving. Not sure the PI likes infrequent use or long winter layups though.

Peter

[Madmal]

Hi Mal,

 

I have to agree with the points that Tom made! Altitude is a real problem for the standard PI metering unit, as a number of our Group found out on their Swiss Trip All 6 cars suffered plug trouble.

.But, in my view before deciding which way to go. What is the condition of your engine, regarding compression and inlet manifold vacuum, etc.? These are key points for the Lucas PI system to work properly. Do you know why that owner went over to Carbs?

 

Bruce.

Hi Bruce,

The car is a November 1971 UK spec with matching CP numbers so I'm assuming 150bhp. It seems that the engine was overhauled in 1999, new big ends, pistons etc and then had a body off overhaul in 2007. The photos show the car with injection during dismantling but only one fuel line was installed so I guess it went to SU's during the rebuild. Has covered less than a 1000 miles since then but no smoke on start up or overrun and seems to pull cleanly so hoping engine is OK. I'll check compression to make sure all is well.

Cheers

Mal

[vitessesteve]

Mal, Don't forget the disy pedestal, that might be tricky to find. Peter

I bought a new alloy one from Canley Classics a while ago. A well made component worth checking if still available.

[elclem1]

Hi I have a 6 with webers that I use for hill climbing and messing around on the back roads here, my wife has a CP 6 with injection which we use for long tours and going into the mountains. Both are great, the injection system was set up and left alone 10 years ago when I restored her car, apart from a couple of injectors sticking last outing it has been fantastic, so my advice is if it's working why break it.? If I was honest the injection wins over webers just! That said SU,s are great for long tours and fuel economy. Sorry but I guess that isn't too helpful. Things only get expensive on a 6 when you can't do them yourself. Andy

[Andy Moltu]

I would have thought the call should be between PI & efi.

The former simple and original, the latter more efficient.

 

These days the triple carb option would seem like an expensive and probably thirsty option.

[elclem1]

Sorry astontr6 but I disagree about altitude, I did French,Swiss and Italian alps last year in my wife's cp injection 6 it didnt miss a beat. It's a standard system as was in 69. However I did compleately overhaul it when I did the restoration in 2006. And I have an ally fuel tank maybe that's the difference?

[Alec Pringle]

Read what it said on the original tin . . . . . Triumph TR6PI . . . . .

 

Set PI up properly and it works, and it doesn't have much of a problem with altitude either . . . not as long as you keep your foot down . . . . .

 

Cheers

 

Alec

[elclem1]

Hi Alec it is a triumph tr6 cp PI,

[Alec Pringle]

Indeed so, but CP wasn't part of the original nomenclature . . . . . .

 

The significant clue lies in the PI . . . . .

 

All too often someone buys a TR6, CP or CR, and doesn't quite grasp the significance of the original PI installation, a full race Lucas F1 system by origin that only Maserati and Triumph ever succeeded in adapting and applying to a production range . . . . . if you could ever have called 1960s Maseratis production cars !

 

What we now all too often take for granted was a thing of pure wonderment back in 1967, teenage boys and grizzled veterans alike gazed in awe at the PI system under the bonnet of TR5 . . . . . and then the following year we were even more astounded to find almost the same engine lurking under the bonnet of the hitherto mundane Triumph 2000.

 

That was our heritage, an engine that broke the mould, and love it or loath it the six-cylinder 2498cc PI engine in whichever format was a radical innovation back in its day, and the single best reason for owning a TR5, TR6 or 2.5 PI today . . . . .

 

Cheers

 

Alec

[elclem1]

Sorry Alec I should have said - a PETROL INJECTION 1969 tr6 it is a CP numbered car' nominally 150bhp it goes up hills very well, such as the alps or here in the Pyrenees. I have no problems because it is set up correctly. So do I have the correct tin ?