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TR6 TR6 Weber 40dcoe HELP


Darth Vader
is any one running weber 40DCOE on a stock TR6 that can help with getting these running ok,or is that not possible?
additional: 3-28 I am waiting on a carter fuel pump, and MSD spark unit. The distributor mechanical advance was frozen but got it free and working past weekend, thanks for the emails, keep them comming also is anyone has spare jets that they would be willing to sell or loan out I would apprecite and we can work out payment thanks


Chassis Dyno, good amount of Weber tuning parts, someone with good Weber experience, patience and good luck.



Darth Vader
I might have to do the rolling road but I was hoping someone has actually got a set and could give me the jetting numbers and compare them to what I have, thanks


Jedi Warrior
With 10/1 compression, 1.65 roller rockers, headers, 2 1/4 single pipe, here is what worked best for me. Chokes-30, venturi-45, Mains-135, Emulsion tube-f7, Idle jet-f11, Accelerator pump 45. Very strong through all rpm ranges, good Idle, spark plugs with light grey color. Gron Perry from Pierce Manifold in Gilroy CA. (Weber experts and parts supplier) dialed me in on this set up. The only luck you will need is if you go back to Strombergs.


Luke Skywalker

/ubbthreads/images/graemlins/iagree.gif Ideally you should put the car on a dyno and tune specifically for your engine *in its present condition*. Best would be a shop with a dyno that also has a good supply of Weber jets and knowledge of the carbs, so they can swap them around without you having to buy a bunch of extras just to give them a try. Tuning Webers yourself by pulling the plugs and trying to guess what will work can end up being very time-consuming, expensive and frustrating!

However, below are the *initial* setup specs for stock TR250/TR6, per a Weber manual.

First of all, you should have triple 40DCOE2 model carbs. I think in most cases the "2" at the end designates the float bowl capacity and range of the floats themselves and/or the method of cold start fuel enrichment. It's quite possible other models like 40DCOE18 will work, but they also might give some unexpected results.

Here's what's recommended by Weber for stock TR6 with triple 40DCOE2, and I would guess these are for a car operating at sea level:

chokes (primary venturi): 27
aux. venturi: 4.5
main jets: 1.30
emulsion tubes: F2
air correction jets: 1.60
idle jets: 0.50 F11
accel. pump jets: 0.45
accel. pump air inlets: closed
needle valves: 2.00

Again, this is just a starting point and many other factors come into play with Webers. Racers who use Webers usually have a box full of jet sets to swap around for different track conditions: altitude, ambient temperature & humidity, etc. Changes you make to your car - such as installing headers and a freer flowing exhaust system, adding velocity stacks, increasing compression, porting, going to larger valves, etc., etc. - will require retesting and, most likely, re-tuning.

A few other details:

Also check your fuel pressure is relatively low, between 2.5 and 4 psi if memory serves. If it's higher, install a fuel pressure regulator or the carbs will flood.

And, folks sometimes don't install any support brackets for DCOE and end up regreting it when the flanges of the carbs snap off due to engine vibration. (Must admit I ran DCOEs without any support bracket for years on my TR4 and was just plain lucky. Not wanting to trust my luck any longer, I finally fabricated and installed a support.) The reason a support should be provided is because the carbs stick out so far from the side of the engine. The support should have some sort of shock mounting.

There are special sealing gaskets and rubber shock-isolating mounting pieces used at the manifold, too.

If you end up rebuilding the carbs, rebuild kits can be purchased with or without new needle valves.

One good argument for sending the carbs for a professional rebuild is that there are a number of special tools - used to reform jet seats, etc. - that would be very expensive to collect to do all the work yourself.

Heat shields can be a very good idea, too, although a stock, cast manifold doesn't transfer as much heat to the carbs, fuel lines and intake manifold as tubular headers would. (Last I heard from him, Joe Alexander at https://www.the-vintage-racer.com had come up with a prototype and was thinking about producing Weber heat shields.)

There should *not* be a vacuum takeoff from the intake manifold, for distributor vacuum advance. The dizzy itself should be modified to work with only centrifugal advance, not vacuum.

You might also find it very useful to pickup a copy of the Haynes Weber Carb Manual, if for no other reason than to understand in general how these carbs work and what the various jets actually do. There's even a Haynes manual covering Webers, SUs and ZSs, all in one book. There are some good websites with Weber info, as well, you might want to do some Googling.

Finally, I think most folks find Webers' cold start enrichment circuit (actually like a mini-carb itself) isn't all that useful. I've never even hooked a cable up to it on my TR4. I always got by just fine with a couple pumps of the gas pedal and then by holding the pedal to a slightly higher idle briefly after starting, maybe for a minute or so.

Hope this helps!



Jedi Warrior
Alan, thats alot of good info and a good point to make about the fuel pressure. The numbers you gave should be good for a stock motor. yes-a dyno would be ideal, but I think a reasonable tunning job can be done without it. With the Haynes Weber manual and/or the Pat Braden Weber manual you can get a good idea on how to tune without the dyno. Even with a dyno you are going to need alot of extra jetting parts to get it dialed in. Good point on the vibration problem although it is not as critical on the tr6 but still a good idea to have a support.
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