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Thread: twin 40 jets any good?

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    Mechanic marshyboy2002's Avatar

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    twin 40 jets any good?

    Hay guys have taken one of the carbs now to go for the rebuild and just wondering the jets are sized right for the 2l pinto
    Jets are
    Progression 60 f5
    Pump jet 45/35
    Main jet f16/125
    Idle jet 45/f8
    I would say now is the time to change them if needed as I will keep them as spares when I change to 45s

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    Re: twin 40 jets any good?

    Ill be in the same position soon, although I have a big valve head and newmans 272 cam

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    Re: twin 40 jets any good?

    Quote Originally Posted by marshyboy2002 View Post
    Hay guys have taken one of the carbs now to go for the rebuild and just wondering the jets are sized right for the 2l pinto
    Jets are
    Progression 60 f5
    Pump jet 45/35
    Main jet f16/125
    Idle jet 45/f8
    I would say now is the time to change them if needed as I will keep them as spares when I change to 45s
    What size chokes?

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    Re: twin 40 jets any good?

    Ye didn't check that I'll look when I get back tonight

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    Re: twin 40 jets any good?

    Just found it on a photo on my phone
    Chokes are 34

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    Re: twin 40 jets any good?

    How do I check what chokes are in mine?

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    Re: twin 40 jets any good?

    There will be a number stamped on the choke
    If u remove a trumpet/air filter u can slide the venturi out and then slide the choke out and have a look or u may be able to look inside with a torch or even a mobile phone on record if space is limited

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    Re: twin 40 jets any good?

    Cheers I'll have alook

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    Re: twin 40 jets any good?

    Hay guys are these sizes any good before I buy some new ones the same

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    World Champion Decade Plus User alladdin's Avatar

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    twin 40 jets any good?

    I think the 50 f5 is the choke enrichment.
    Mains look ok what about air corrector at top of main stack

    Idle I see 55f8 spoken of but I can only repeat from reading up.
    Hopefully someone with actual experience will pop in.
    Last edited by alladdin; 13-12-2015 at 15:12.

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    Re: twin 40 jets any good?

    All right are u saying use 50 f5 instead of 60f5

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    Re: twin 40 jets any good?

    its been a very long while since i did anything with carbs, so im very rusty/forgetfull but, on 34 chokes i would think the mains are a tad small, and idles probably want changing from 45 f8 to 50 f9. but tbh i would recomend buying jets on the basis of my poor memory alone

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    Re: twin 40 jets any good?

    Will have a look what I can get off the net tonight
    Now the car is motd I have been out and about in it and it seem the more I'm driving the less it's hesitating although it's still there and I'm happy with how quick the car is so would I be right to change the main jets or am I'm barking up the rong tree as I'm as green as it gets with the carbs

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    Re: twin 40 jets any good?

    if the problem is only a tiny throttle openings, the the issue will be the idles

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    Re: twin 40 jets any good?

    Cheers graham

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    World Champion Decade Plus User alladdin's Avatar

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    twin 40 jets any good?

    Have you checked the accel pump jets arnt blocked ? Look into carb and snap throttle open, you should see 4 squirts one in each

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    Re: twin 40 jets any good?

    Transition has all to do about idle jet, progression holes, position of the throttle plate and model throttle plate. So it's almost impossible to give correct advice unless the carb is a well know model. Sadly the best know model for 40 and 45 are the new ones. There is mainly only one 40 mm DCOE and unfortunately a very poor build carburetor. I strip them to the bottom, build back up as it should and ALWAY have to make mods to the prog. holes, throttle plate angle or any other mod to make it work correct.

    This is probably the carb all others will use as a reference when they give you idle jet advice (yes you can make them run as it comes out of the Weber box but many points will be very to extreme poor tuned). It will only run. If this is a race or track day car it's OK but for a road car, not so sure, they run a lot in this transition position. But what if the carb in front of you is NOT the new Weber. Let say an old Alfa or any of the few hundred different models they have ever build. Total different story. Very difficult to give advice.

    Most 40 DCOE share the same main circuit. Easier to give a basic jetting. I would also start with a richer main jet and work down worth until it"s correct. But what size is your air jet?
    Last edited by Dyno; 13-12-2015 at 19:08.

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    Re: twin 40 jets any good?

    Alladdin I'll try and catch that on camera to c now
    Onyd I'm not sure I'll strip one Down shortly and report back

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    Re: twin 40 jets any good?

    Alladdin Defo spraying fuel from all 4 bud

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    Re: twin 40 jets any good?

    Is the air jet at the top of the emulsion tube if so they are 160

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    twin 40 jets any good?

    That's the one

    I have a set of 40s I am cleaning now with smaller ones than 160 but I think drilled out
    I have got some micro drills off the bay to check them.
    180 seem commonly recommended.
    I managed to pick up some 30 chokes cheap too as its for a std pinto
    Last edited by alladdin; 13-12-2015 at 20:31.

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    Re: twin 40 jets any good?

    What mm are we talking bud

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    twin 40 jets any good?

    A 150 jet is 1.5mm
    180 1.8 etc

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    Re: twin 40 jets any good?

    Nice one bud

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    Re: twin 40 jets any good?

    New idles and air jets on order although I did drill the old ones and it throttled reasonable well it would not tick over and the fumes was unbearable will post how the new ones go

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    Re: twin 40 jets any good?

    Well I have put 50f9 idles and 180 air jets in today and what a difference the car is running a lot better although every now and again if I'm staying at lowish revs I still get that one cheeky little pop butt it's a hell of a difference driving it now
    And driving it out on the public road of course I drove sensibly cough cough

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    twin 40 jets any good?

    Is it a std engine ? Just curious , sorry if I missed it previously

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    Re: twin 40 jets any good?

    Air correctors won't do much to low speed running, their size depends on what main jet you use, tune low end first, get idle jet transition to main sorted first then fine tune Afr by adjusting the corrector size, a 140-145 main jet with a 180 corrector should be close, 40 pump jets, and a 50 f8 or 9 should work fine until you get it on the dyno
    Last edited by Erikmex; 17-12-2015 at 17:01.

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    Mechanic marshyboy2002's Avatar

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    Re: twin 40 jets any good?

    Quote Originally Posted by alladdin View Post
    Is it a std engine ? Just curious , sorry if I missed it previously
    Standard pinto block with ported and polished head and a piper cam 285 I think

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    Re: twin 40 jets any good?

    Quote Originally Posted by Erikmex View Post
    Air correctors won't do much to low speed running, their size depends on what main jet you use, tune low end first, get idle jet transition to main sorted first then
    fine tune Afr by adjusting the corrector size, a 140-145 main jet with a 180 corrector should be close, 40 pump jets, and a 50 f8 or 9 should work fine until you get it on the dyno
    Will get to a dyno in the new year hopefully for the man in the no to do his stuff ��

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    Re: twin 40 jets any good?

    Best way, even when you think you've got it pretty close you can still be far off when you hook up an AFR meter and do some runs. I usually jet my engines on the rich side then get them on the dyno.

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    Re: twin 40 jets any good?

    Mine ended up with 45f8 idle and 140 main with 180 air correctors with 32mm chokes I hink

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