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Gt6 Triple 150Cd Strombergs

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I am hoping to get some feedback from GT6 owners that are currently running triple Strombergs. How pleased are you with the conversion, was it worth the expense?

 

Since I already have a mild cam and header, a triple Stromberg setup seems to be the most logical and cost effective next step to improve my engine's performance. Richard Good and Jeff Palty in the US post-1215-0-90008800-1357484606_thumb.jpgeach have decades of building Triumph 6's, and although their main focus is the larger TR6 engine, they claim that the triple 150CD setup has been very effective with the 2L engines.

Also, 150CD's are shorter and fit under the GT6 bonnet without modification.

I know a popular upgrade to series II E types is to revert back to the triple carb setup of the series I cars - that has to tell you something (I would think)?!?

 

From Richard Good's site:

The Triple Stromberg System has grown steadily in popularity since I introduced it in 1991. More and more TR6 owners are realizing how well it performs, offering the high performance they want without a sacrifice in fuel economy or street manners. I have had great success using this system on high performance TR6 engines that I have built and have received excellent reports from customers who have installed the kit on their engines as well. I have always worked with the 175CD's but some of my customers have had equal success using SU HS6's. Strombergs and SU's have a sliding air valve creating a variable venturi to maintain high air velocity across the jet regardless of the volume of airflow. At idle when the engine is using very little air the air valve is only open a crack so the air still rushes past the jet to properly mix the fuel. As the throttle is opened and the load on the engine is increased the air valve rises, riding on the airflow to maintain velocity. At full throttle under load the air valves are fully open exposing a wide-open passage for air. This performance simply cannot be matched by a fixed venturi carb. If a fixed venturi is sized large enough to provide adequate flow at high rpm it will not mix the fuel properly at low rpm resulting in poor fuel economy. With triple Strombergs the fuel mileage is generally in the mid 20's and the performance is fantastic with instant acceleration and smooth power throughout the rpm range. Installation is easy with no modifications required to the stock carburetors. This system is a worthwhile improvement to a stock engine and is of even greater benefit to a modified engine.

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Best you hear from Bruce and his tale of triple SU's. I don't think it was at all easy with many hurdles to overcome along the way.

In fact, you may turn the episode up on here with a search......

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Here are a couple of previous discussions on the subject

 

http://sideways-technologies.co.uk/forums/index.php/topic/1813-inlet-manifold-balance-pipes/page__p__23603__hl__+fuel%20+standoff__fromsearch__1#entry23603

 

http://sideways-technologies.co.uk/forums/index.php/topic/763-fuel-stand-off/page__hl__%20fuel%20%20standoff__st__60

 

Some of the pics have become detached when the forum was moved a while back.

 

I think that the bottom line is that the triples can be troublesome.

 

There are other, certainly simpler, certainly cheaper, to get similar results from twins. You can fit 175s to the standard manifold. You can fit 175s to the standard manifold and open it out/port match. You can use the TR250/TR6 manifold with longer runners and 175s (my favourite - could be bonnet clearance issues with the front dashpot though). Do be aware that some (but not all) US market TRs have different port sizes and spacings so check any TR manifold you buy matches your head before parting with cash.....

 

Cheers

 

Nick

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The exhaust header pictured has two groups of three cylinders. With two carbs each is effected by an evenly spaced negative exhaust pulse. With that exhaust the middle carb will receive an irregular pulse from each half of the exhaust and also possible upsetting the outer carbs.

If you feel your engine could make more power if it could ingest more air maybe a switch to 175 ZS or HS6 is the answer?

Three carbs look great but even with a 6-3-1 header -3 groups of two exhaust primary pipes- the middle carb will flow differently than the outer carbs.Not an impossible problem but will it make more power?

I recall several past discussions on this subject with better explanation of the pit falls.If you go with 3 carbs switch the Ex. manifold.

Edited by motov8id

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This triple carb set-up cannot work, doesn't matter who claims what.

(The US vendors of this don't have proper TR6 Pi with which to compare).

 

The stand-off issues got me thinking for months and months and have NOTHING whatsoever to do with balance pipe size.

It's the carbs and their mode of operation that is to blame,- (stupid!)

 

Without wishing to go into the intimate details of why this stuff will never work

(and why E type Jags/Healey's sort of function in a bodgy kind of way), you have to understand the way the CD carb works and how it all falls apart the moment you start opening the venturi really wide.

I won't even mention the diabolical design issues, which make the manifold incapable of flowing air except round and round in circles.

 

So, right,-

If you want the engine never to work at full throttle, and deliver some extra torque up to about 1/2 throttle and look very blingy and powerful, it's for you.

Plenty of people fit into that category, and don't care if it doesn't work.

 

If you want it to deliver decent torque, go get the twin SU manifold fitted to the later cars with long branches.

 

It will require plenty of attention also, to get it to flow right but will WAY outperform this dumb triple carb setup.

I've seen as much as 165bhp from a vanilla TR5 engine on 2 HS6 carbs & the 6-3-1 system.

(Nigel G claims more from his 2L).

 

As far as I am aware, no-one with that triple set up has squeezed more than about 130bhp.

I did manage to hit 155 from the 2L with all sorts of troughs and peaks, 2 weeks of extra work+masses of TIG welding and some "trick bits" about 3yrs ago.

 

I would never do it again..(something to do with not getting paid if you remember)

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Good for a friend of mine who did not know that it does not work and knew nothing about the negative comments

when he installed the 3 carbs with the goodparts manifold and used three 44HIF from the Rover SD1 on the TR6.

Just from the beginning the performance, behaviour and fuel economy was better than original

(with the 3-2-1 manifold by the way).

 

In my opinion it depends more in what shape and setup the original two carbs have been

compared to the new ones and how it was managed to get 3 totally equal carbs from the market.

 

Last great influence will be how much work and how good work

somebody is willing to put on to the setup for the new system.

With no doubt a carb from another car needs that setup essentially to perform well.

It would be a rare event to have a plug and play solution.

If it feels that way I would suggest to try out other needles to learn what potential is still hidden in the carbs.

The wideband oxygen sensor is essential for that (Innovate LC-1 or similar)

 

With no doubt it can work very nicely and be very reliable. I have seen that!

In my personal opinion it is the half step from twin carbs to fuel injection

and just a little bit below the Weber 40DCOE which again are the half way from 3 carbs to fuel injection.

 

But with no doubt the steps are so narrow that a perfect setup of twins

still will outperform a bad setup of a fuel injection!

Difference from two carbs to fuel injection on a stock TR6 is about 20HP,

increasing with modified engine needing better breathing capabillities.

So I would expect a bit less than 8HP from 3 carbs on GT6.

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In my opinion it depends more in what shape and setup the original two carbs have been

compared to the new ones and how it was managed to get 3 totally equal carbs from the market.

 

I have seen that!

In my personal opinion it is the half step from twin carbs to fuel injection

and just a little bit below the Weber 40DCOE which again are the half way from 3 carbs to fuel injection.

 

But with no doubt the steps are so narrow that a perfect setup of twins

still will outperform a bad setup of a fuel injection!

 

Difference from two carbs to fuel injection on a stock TR6 is about 20HP,

increasing with modified engine needing better breathing capabillities.

So I would expect a bit less than 8HP from 3 carbs on GT6.

Look, you are comparing apples with oranges again.

 

The twin carb setup people take off is almost invariably a completely STOCK worn out piece of rubbish.

On that basis alone, and the well known fact the original manifold restricts 2 out of the 6 cylinders by as much as 35% how on earth can you compare anything at all?

 

I very adequately proved merely flowing the original stromberg manifold worked so brilliantly, the standard (150) carbs were immediately completely maxed out.

The original engine in fact already needed 2 x 175 carbs doing that mod, FROM THE FACTORY, and that was a 2L bog standard GT6 engine.

Then we come to the airbox which originally is completely inadequate at anything over 3500rpm.

 

Hence people believe there is a miracle happening when you actual equalize the flow of 3 carbs/6 ports and put an airbox on which hasn't got peashooters as pipes coming from the outside air.

 

I would take a bet on it, I can rival any day of the week a properly modified twin carb set-up against that triple piece of rubbish and win hands down every time in both economy and driveability.

Wanna take a bet?

 

In fact as you may recall, Mr Gair, showed pretty conclusively how to get around 170bhp on a 2000cc road car with just a decently modded head, inlet manifold and a properly sized airbox....how?

2 x HS6 carbs, a Mike Randall (mild steel) exhaust and some common sense.

 

3 carbs? it's just another rip-off job to sell a heap of rubbish.

 

Check some figures.

The XJ6 S3 engine on EFI with a tiny single butterfly/plenum makes just as much power as those over hyped E types with triple "bucket brigades" and uses half the fuel.

 

Don't believe a word of the original Jaguar figures

(!265bhp never existed, all they ever made was 200Bhp DIN!)

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Right Gareth, but as I said earlier at another forum:

People like me prefer "straight forward" tuning.

We do not have an engine bench or a flow bench and will not change cams, heads or manifolds several times.

We are more or less "users" who like to benefit from some more HP.

 

If I go for more displacement or change from carbs to PI system with MegaSquirt

I definitely go some steps forward and get more HP.

If I work a bit on the head and increase compression ratio and do a good 3-angle-valve-job

it is the same: Definitely a step forward!

So is the change from 2 carbs to 3 carbs on a mild tuned engine!

 

This is not so if I try to climb mountain territory

with squezzing out the last HP from the 2-carb-manifold or the head.

There you might have to deal with steps backwards unless you know what you are doing.

 

Look how shiny the tripple carbs can look:

 

gallery_1588_1_673117.jpg

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Look how shiny the tripple carbs can look:

 

Big deal, if it comes with a 30bhp "DEATH".

 

Look at this instead.

The Late USA TR6 comes with EXACTLY the right kit apart from sending the Strombergs for alloy scrap, and the camshaft for iron/steel to build some more reinforced concrete in China.

 

triumph-tr6-federal-engine.jpg

 

Here it is apart from sending the "yuck" rocker cover for alloy scrap as well & the "foul" grainy image.

 

Cheap, cheerful, and much more efficient than the triple trouble, with its wrong length inlet tracts.

 

TR6_Engine_C.jpg

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In my limited tuning experience on TR6 the Twin Carbs always limited the power.

My favorite is the Megasquirt + PI manifolds gaining a huge 25HP on my 2.7 litre

over every Twin Carb solution and cost half the price of the WEBER.

 

3 carbs is neither my solution nor did I tell somebody to use that.

I just wanted to show "docman" that there are solutions that work properly.

More or less with the hint not to blame the 3 carbs when it is not perfect from beginning.

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Hello,Wow I think I was almost getting some concussion there! Anyway, I am rebuilding/upgrading/was upgraded in US  TR 6 motor (I am in Australia)and I have a "long"inlet manifold and 2x2" SU's to fit when it's finished so will be interesting to see what I end up with.Regards,Michael.  

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2x 2" is Big for a 2.5 6.unless you are intending to spend a lot of time in the upper rev band range (where 2.5's aren't that happy without a lot of work)My prediction is that below around 2k rpm the airflow through each carb across the bridge around the jet will be so slow that atomisation will be a real problem, not saying it won't run but getting spring/damper rates anywhere near sensible could be fun so that when you open the throttle and want acceleration, you don't get an instant rich or lean bog. If it was me i wouldn't even attempt setting them up without fitting a wideband AFR sensor, could save you weeks/months of head scratching/blind experimentation.

In fact if it was me i wouldn't fit them until i'd proved that the engine i'd built had run out of head room on the existing carbs, like manifold vacuums increasing at high rpms. a just big enough carb will normally give best pick up mid range acceleration but may restrict top end, too big a carb normally gives you the reverse, getting a bigger carb(s)to perform across the range is fun believe me !

alan

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Agree with Alan. Unless building an absolute monster (and that should have triple Webers/Dellortos or FI) 1.75” will be enough and easier to calibrate.

Wideband AFR meter is a great tool whatever you are doing....,

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