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Delving into the dark art of fitting triple Webers to the 6 Pot TRs reveals a huge combination of set ups!

I have 3 x 40 DCOEs 151s with 30mm Main venturi, 4.5 Auxiliary Venturi, 40 Pump Jets and F9/45 Idle Jets and standard progression holes, What combination of the following would give me a good start for tuning? Touring and Local Show stuff, definitely not Racing (although the odd track day might be fun). I have deliberately not put down what I have fitted already but have got the tick over slow running working nicely.

  • Needle Valve size
  • Air Corrector Jet size
  • Main Jet size
  • Emulsion Tube size/pattern.

 

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I was told there are 4 billion permutations for the DCOE ^_^.

If you have the CP cam and c/r per original the setup I have in my driver '250 with CP cam and wide port head can be a guide:

125 main

175 air

F7 emulsion tube

closed pump bypass

45 pump jet

175 needle valve

30 chokes

60F4 idle ( these may be scarce - 50F9, 55F8 are similar ).

This recipe has given joy for 95,000 miles and counting!

If you have a true extractor manifold like a GOODPARTS the main jet may need downsizing from the above.

 

Tom

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Hi Dave,

Looking forward to your fire up someday; there are several others going this way I'm in touch with. Might not be a wave yet but the trend is good!

 

For Uncle Pete:

Float level is critical; for the 40DCOE151 I believe the setting should be 12mm by the book method. For sure the height of the fuel below the top of the well ( where the main stack screws in ) should be 27-28mm, all equal. A makeshift dipstick is used to gauge this.

 

Tom

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Thanks Tom and Tush

Bit more spec for you; 1969 CC engine with wide port 2500S head. Original CAM. Extractor Manifold.

Fuel level 29 - 30mm below collar of access cap.

175 needle, 115 main, 200 air corrector, F9/45 idle jet, F11 Emulsion - anything there make you raise your eyebrows?

The inlet manifold is a Bastuck with solid rod throttle linkage bar. I have installed adjustable rose jointed linkages to each carb, although this would seem to me, to make the connection solid between each carb! Is it advisable to have a little slack at fully closed throttle?

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16 hours ago, roy53 said:

1969cc ?????????????????????

Hi Roy

1969 TR6 CC USA car fitted with carbs. as against a CP, CF or CR.

I popped an endoscope down the inlet track of the manifold and all checked out OK by the way.

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Hi Peter,

The CC engine with its 8.5:1 c/r and 10/50/50/10 cam is a poor candidate for triple Webers; the best that can be achieved is parity with the stock carbs. Sorry to be the bearer of...

If it were mine I'd get the head shaved to 9.400" thick and fit a CP cam or comparable. Then the Webers can do their thing and deliver full on CP performance once dialed in.

All the jets etc. you list are for the LOTUS ELAN engine; only the 30mm chokes are applicable in my experience and may need to drop to 28mm. I haven't dialed in Webers for the stock emissions engines though I drove one which was and it ran fine albeit was no faster than my stock '250. I don't know what its jets were.

Fuel level height should be measured from the top of the well where the main stack screws in. I don't have a reference dimension for the collar you mention.

Cheers,

Tom

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Have have not touched my dcoe configuration since 2012. This is how they are set up:
 

Chokes 30mm

Aux 4.5

Main 140

Air 160

Emulsion F11

Idle 55F9

Accelerator pump 50

Pump exhaust closed (made a big difference)

Float height (Spanish carbs, plastic floats) 7mm/15mm

Idle mixture screws 2 turns out from fully closed

Goodparts GP2 cam, 9.6:1 compression

 

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On 11/22/2020 at 6:19 PM, Tom Fremont said:

If it were mine I'd get the head shaved to 9.400" thick

Hi Tom

I might not have mentioned earlier that it has a higher compression head fitted (219015 TR6 PI CR) with a Compression ratio of 9.5:1. I'll work with the existing Cam for the moment.

Reading all your recommendations and various Journals I have put together the following set-up from the bits I have.

30mm main venturi, 4.5 Aux Vent, 125 Main jet, F9/50 Idle Jet, 180 Air Corrector Jet, F7 Emulsion tubes. I have managed to source and am waiting for F4/60 idle jets.

After checking all the fuel levels and screw settings, I ran her up yesterday. She started OK with plenty of popping, so I initially wound all the idle screws out a 1/4 turn which calmed things down a bit! After warming her up, I then adjusted the idle screws on each cylinder by 'feel', once happy with this - and the air flow between carbs - and the tickover, I then put a Colourtune on each cylinder in turn. I was quite pleased how my 'Feel' setting and the Colourtune indication matched up at Idle. I took her for a run and was pleased with the progression and flat out phases, although I would say it's work in progress!

 

 

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On 11/20/2020 at 3:59 PM, Tom Fremont said:

closed pump bypass

 

On 11/22/2020 at 7:50 PM, foster461 said:

Pump exhaust closed (made a big difference)

Guys

Is this the same thing?

I cannot find reference in any literature I have?

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3 hours ago, unclepete said:

 

Guys

Is this the same thing?

I cannot find reference in any literature I have?

Yes, it is the same thing. There is a jet in the bottom of the accelerator pump circuit (one per dcoe) that bleeds fuel off back to the float chamber. It comes in various sizes including a blank jet (no hole) that bleeds no fuel so everything from the pump gets inhaled. Listed as a pump spill on some dcoe diagrams.

Stan

Edited by foster461
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Situation so Far - Mk 2 PI head, Extractor Manifold, CP Camshaft 35,65,65,35, 30mm Venturi, Needle 175, Main 125, Air Cor 180, Emulsion F16 (tried the F7), Idle F4/60, Pump 40, Bleed nil.

Very pleased with running and about where I want to be. Gentle to brisk increase in Throttle, provides smooth response right up to 4500 rpm.(as far as I want to take it).

However if I stamp on the throttle there is a lot of hesitancy? I am thinking about increasing the Pump Jet? or reducing the Air Correction Jet?

 

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Could be too much or too little on the pump jet, if all else is ok I would go for pump jet.

Just check that the outlet of the spray hole in the pump jet is facing the right way squirting into the engine, I had one that was on the wrong side, squiring into the aircleaner!

John

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What about ignition timing? Book says at idle 4 deg ATDC with a strobe or 12 deg BTDC static.

I have an electronic Power Spark ignition Dizzy with Vacuum Advance, the manufacturers have said that leaving the Vacuum Advance disconnected is not a problem.

There is no vacuum take off with triple Webers, so what are your thoughts?

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10 minutes ago, ntc said:

With your setup you need 11 strobe btdc at 800rpm

Vacuum connected/disconnected? I do not have a Vacuum take off with the Webers!

Edited by unclepete
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Hi Peter,

My pump inlet valves have closed bypasses. Try this to resolve your " stamping " hesitancy. All else is on par with the setup I have on my driver with the same cam and c/r.

I never had any luck with the F16 emulsion tubes; with these mine would fall flat on their face at WOT. What happened with the F7s?

Tom

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