TR6 Conversion to SU carbs

[cotswold]

hello wise ones,

Today I bought a yellow 1975 TR6 It is running rough and missing occasionally on a couple of cylinders and whilst I will go through the electrics and ignition to eliminate issues there I have never warmed to PI and would like to know if anyone can tell me what I would need to do (and roughly what it would cost) to convert to SU carbs. I understand that twin SUs give better fuel consumption than Strombergs and are more reliable than Webbers.

Thanks

Charles

[mike barrett]

I would give the PI a chance. Its actually not that difficult to sort and does give much better performance.

I have had a PI for about 2 years and really like the injection system (having had carbs on a 2.5L GT6 and Vittesse), its not perfect but can work very well.

So what the issue with your car?

 

cheers

mike

[Red 6]

I have travelled this very route.

 

Search out a pair of SU's with manifold from a triumph 2500 saloon (obviously the card version not the PI) and bolt them on.

 

Get an electric petrol pump and plumb it in, you wont need a return pipe to the tank.

 

You can remove the MU and pedestal so the dizzy sits directly on the block.

 

There is a vacuum advance take off on the manifold which needs to be blanked off or connected to the dizzy. I ran mine blanked off.

 

You can buy an accelerator cable and cut it to size and a 2nd one for the choke mechanism.

 

The su manifold is water heated so that needs to be plumbed in. When refilling with water it is best to backfill rather than via the radiator as you could get an air lock.

 

So it really is straightforward although my response is from memory.

 

It should run fine from the off and you can play with needles and advance curves at a later date.

[John Bracher]

Hi Charles.

+1 for the previous post.

Helped a firiend do the same some years ago.

The only "non saloon' item(s) were some decent K&N air filters, as the saloon ones didn't lend themselves to good breathing compared to 'more open' ones.

Ran fine after some fiddling with mixture, possibly due to cam timing?

If you do change from PI, let me know by message, will possibly buy all your castoffs!

[cotswold]

Thanks very much Red 6 that is very helpful indeed. I will try and give the pi some attention Mike to see if I can get it running ok but won't spend too much time and money on it. John thanks but I would probably keep the old set up.

Cheers

[RogerH]

.....or TRiple SU's as per E-type and a certain TR5.........

 

 

Roger

[cotswold]

Hi Roger, yes I did consider that but read that you would need a tanker tender!

Regards

Charles

[TriumphV8]

1.) The Strombergs: These seem to have the rubber diaphragm

broken or the fuel supply is broken. Cheap to fix and a good idea anyway

to sell the Strombergs probably later and so can tell they worked on your car.

Anyway the reason for stumble must be found before changing things, thats the rule.

 

2.) The PI: Although claimed to be unreliable in these days they work nice and

can be made nice choice especially with the BOSCH fuel pump. Anyway

do not underestimate the work and costs to let it fit in the car.

A not overhauled and proper setup PI is a pain! So here especially: Build it right or forget

 

3.) The tripple SU: Despite some rumours that they do not work according to the wrong

following of suction of cylinders they do their job properly, power increases and fuel

consumption can be made perfect like Stromberg and Pi, too

 

4.) The Weber: They are expensive and only few people can set them properly

that you have power and low fuel consumption. In these days I would recommend

to those who have them fitted to keep them and others should swap to electronic

full engine control with MegaSquirt or similar. This has the perfect fuel injection,

the test bench and the perfect ingnition similar but superior to 123tune already on board

and it is much cheaper than the Weber and easier to setup when fully understood.

 

My recommendation is to look after the diaphragms and leave the rest till winter

and make a well planned decision mavbe guided by some bargains found at Ebay.

Edited September 26, 2015 by TriumphV8

[john.r.davies]

You need to get together with fredell, who is doing the swap the other way: http://www.tr-register.co.uk/forums/index.php?/topic/53756-2500-pi-and-tr-6-engines/

 

John

[Steves_TR6]

I'm a convert to the PI system.

 

My natural inclination would have been for triple webers, always fancied DCOEs!, but after three trouble free years and more than 10k miles with my PI car I love it!

 

Get the PI system fettled and use it regularly, you'll love it too I'll wager :-)

 

Steve

[Dave McDonald]

Charles

You have a PM

Dave McD

[Tom Fremont]

Hi Charles,

 

With the CR cam dual Strombergs or SUs make sense.

 

If using a CP cam or hotter then Webers are hands down the optimum solution for:

 

1. Reliability - I have over 110K miles on a set of really ancient 40 DCOEs on my driver with no maintenance in 21 years. Brass floats, ball bearing throttle shafts and way too many ingenious features to list set them apart from the rest of the field. They remain the fuel system to beat on these engines most of a century after their conception.

 

2. Fuel economy - my driver gets 23-24 mpg overall ( Imperial ) and the tailpipe takes a tank of fuel to blacken after wiping clean. No soot accumulation on the bumper, unlike all emissions TR250/6s I've ever seen. I get over 30 mpg X-country ( O/D fitted ).

 

3. User friendliness - mine are DIY calibrated .

 

4. Period correct

 

Six throttles is the end of the line short of supercharging. This means less extreme mods with their attendant longevity shortening issues needed elsewhere for the same power.

 

Carburetors are immune to altitude sickness unlike the LUCAS P.I. Mine have gone over 11,000 ft. without issues ( though as they say, a point of c/r is lost for every 5000 ft. so a little more pedal is needed on hills ).

 

Cheers,

Tom

[cotswold]

Food for thought thanks Tom.

Cheers

Charles