TR6 (CR) Setting PI Inlet Manifold Butterflies

[Chilp3]

Good evening,

I have just spent a rather frustrating few hours this afternoon trying to set the butterflies on my 1973 CR series TR6. First a little background information; the car is fitted with the 'prestige' throttle linkage kit together with refurbished inlet manifolds (3,000 miles ago) and prior to me 'meddling' was running OK with the exception of a little hesitency at low revs. I took previous advice on the forum that the hesitancy could be as a result of the butterflies not being set correctly. To help me with the task I purchased a Dellorto carburretor balancing tool although in reality I think this may have confused me further. What sort of readings should I be looking to achieve from the balancing tool and at what point should I be looking too take readings? I have been working at idle although I suspect that providing the readings are roughly equal across each manifold this will make little difference. Happy to be corrected if I'm wrong here of course.

Firstly I have set each pair of butterflies to just 'grab' a cigarette paper with the throttle closed following previous advice on the forum. When I started the car (with the air-box removed) I was surprised that it fired happily with no choke and had a very high ticker even with the air-bleed valve fully closed. I assume this was because there was air flowing into the inlet manifolds with the throttle closed as I had set them partially open albeit only 2 thou (thickness of paper). Closing the air-bleed valve did not stall the engine so clearly this was not the correct set-up. I tried setting the butterflies firmly closed with no throttle but the car drove terribly and I had to have the air-bleed valve virtually fully open to achieve a reasonable tick over.

I would appreciate some simple step by step instructions to set and balance the butterflies as clearly this makes a significant difference as to how the car drives especially at low revs (so i'm told). In hindsight I wish I had left things alone as I have now rendered the car un-driveable which is a shame. Having said that it would be really great to be able to set the car up properly and get it running properly once again.

Thanks for reading my post and as always all suggestions and/or ideas are greatly appreciated.

Best Regards, Peter

[JohnG]

Peter

Hi

 

Don't know if it helps, but . . . . . . . .

 

I have a '75 CP '6'

 

My car has refurbish inlet manifolds, fitted by Clive Manvers.

His team had problems getting the engine to run slowly and Clive admitted that he made a mistake in having the insides of the refurbished inlet manifolds cleaned.

 

He explained that, as a result of the lack of a build up of contaminants on the inside of the manifolds, a good air seal around the butterflies was difficult.

 

His team got her set up as best they could, within a 2 day time scale

Clive's advice; go out and give it some welly to get a build up started inside the manifolds. This will help seal the butterflies

 

The car runs really well

Starts quickly and reliably

Pulls through the range of revs and pulls like a horse.

 

Only 'problem'; when hot, tick over is about 1050 rpm rather than 800 rpm, with the air valve closed

This has come down from the 1200ish rpm when she left Clives place.

 

I'm happy, things seem to be going in the right direction and that, as usual Clive's advice seems to be good

 

Note

The refurbished manifolds and linkage are all from a '71 car

Edited June 12, 2016 by wjgco

[TR NIALL]

Are you sure the Choke is returning fully on the Cam at the Throttle Linkage and also the Enrichment Lever at the Metering Unit,both need to be fully closed or you'll never get the Set Up right?

[DaveN]

So! If these TB's need to be coked up to get a smooth idle and good light throttle performance, how did ST manage in the early days when the cars were new?

[JohnG]

So! If these TB's need to be coked up to get a smooth idle and good light throttle performance, how did ST manage in the early days when the cars were new?

Don't know

Didn't ask

All I know is she is running better as the miles are put on the clock

 

Clive knew his Triumphs

[barkerwilliams]

Peter,

 

I have a 150 PI 1970, Prestige refurbished bodies and throttle linkage.

 

Engine should not rev more with air box removed - unless you have a really, really, really dirty air filter.

 

The theory is to get all butterflies shut completely (which is not actually possible) so the engine only ticks over on the large air screw which feeds air into the manifolds behind the butterflies.

 

Have you checked for air leaks around the manifold? Unless it is sealed between head and butterfly it will never balance.

 

I did the following:-

 

1 I bought Dellorto carb balancer

 

2 I bought some new butterfly screws as they are quite small and stiff and vulnerable.

 

3 Balanced each pair of throttle bodies at a slow tickover - seems impossible to get exactly the same but can get close. Doesn't matter what the reading is but as low as possible.

 

4 Connect two throttle bodies together with linkage, then when similar reading on gauge connect the third pair.

 

5 Fit (if not there) screw into throttle opening cam for choke.

 

6 Screw this in to raise revs to perhaps 1100 revs and check that all that all throttle bodies are drawing the same (similar) volumes of air.

 

7 Found that a couple of pairs ended up with readings of 3.5 on one and 5 on the it's partner body

 

 

Having tried (and cried) over getting all my pairs exactly the same I thought about the build up of "gunge" to assist with sealing the butterflies mentioned by wjgco above.

 

So I thought I would speed up the process. I thought about using high temp paint, but that would glue the butterfly to the body, and as you opened the butterfly the first time it would rip the paint off one of the surfaces and leave the other surface with a lumpy paint edge. Paint forms a relatively thick coat and I was only trying to simulate the build up of carbon.

 

So I wanted something that would not set, would not glue components together, would withstand a reasonable temperature (D321 is 450'C) and form a very fine film. And if it ended up in the valves / combustion chamber would do no harm.

 

So I ended up with Molycoat - a spray can, some of their products are used to coat pistons and rings to reduce friction (Bentley for one) so it seemed like a no-lose experiment.

 

I sprayed my butterflies on the car.

 

All their product sheets refer to surface preparation and as the TR6 breathers recirculate crankcase oil vapour through the inlet manifold there is a need to remove the oil.

 

So I used brake cleaner - a vigorous blast from a spray can or two over the butterflies and bodies and a wipe out with clean tissue.

 

Then a very fine spray of Molycoat into the throttle bodies with the butterflies closed. Followed by a second fine spray half an hour later. Trying the car out an hour later had a measurably different set of individual flows through each of the bodies. (Dellorto carb balancer). The high reading bodies had come into line with their partner.

 

Yes the butterflies and everything were coated in D321- but is a very fine film and a lubricant. In an ideal world the best would be a ring of Molycoat just around the edge of each butterfly where it touches the throttle body and seals.

 

Car was, and has remained for 4000 miles so much better. More even, as if all cylinders are pulling together.

 

I can't see a down side to using it, an expensive but really good product.

 

 

 

Alan.

[GT6M]

if yer TBs are worn, or moer specific, the spinnals that the butterlys attach too

are worn,{ spinnals alays wear, v v rare the TBs wear, Allyoxide,wears the brass away}

 

How many of you ladds oil yer TBs ona regular basis to stop wear,!! ,mine get done every its going out, teks only seconds

 

then wots happening is on v v low throttle openings, the butterfly nearest the arm will open slightly

befoer the other, so if ye got em all set right, then it could well be running on 2 4 6 cyls at v v low throttles,

 

this cos 2 4 6 = throttles end positions.

If ye tek the log off, put a wee bit of oil in throttle plate base, and move the cable, then what im onaboot can be seen, as oil will move on the link side first.

 

can tek spinnals oot, and re solder,braze, devcon up, then hone to fit better.

I hard soldered mine, work great.

 

also, coat the insides of the butterly area wid a v v thick dry grease

this will bed into worn bits, and help sealing

 

Butt, first, hve a good long hard close Loook at the actuall butterflys,

there is a level bar just above the middle, its quite easy to fit a butterfly in the spinnal, and its NOT level,or sitting right, which means its sitting askew, and will no shut right.

 

gotta slacken off, level up as best as ye can, the, tap top of butterfly, to mek it seat.

 

if oot of the car, can hold em up to the light, and its quite clear then, where they no sealing at.

some good taps can, and does work wonders.

 

I did a wee thread on fettln the manis up a while ago, but can seem to find it noo

 

 

 

M

Edited June 13, 2016 by GT6M

[DaveN]

+1 for Molykote 321r. I have actually used it on the half shafts sliding joints to good effect.

[Stanpartmanpartwolf]

Injection timing is more important for mild short duration cams & I find CR cars idle poorly & respond roughly to small throttle openings if it's advanced- presumably as the fuel lands on a closed inlet valve.

Adhere strictly to the factory timing method.

[GT6M]

Yer on aboot the wrong info given in some books Stanley

cos it does mek a bigg diff, even a 270 deg cam, if timing just matches idle.

ECUs,can fiddle it up / doon till its best,

 

M