Setting the idle twin hS4E carbs

[leon.halliwell]

My Spitfire idles far too low, about 550 to 600 rpm which causes the engine to die if i fully close the choke even when warm, there's a fairly complex explanation of how to set the carbs up in the Haynes manual but i was wondering if you can just adjust the idle screws without fettling with anything else because the car is running with just the right mixture and i don't want it to change.

 

regards

Leon

[DerekS]

If you turn both idle screws clockwise a quarter of a turn at a time until you are happy then don't worry, you shouldn't disturb anything else. Equally if you want to slow it back down a touch, turn both screws anticlockwise 1/4 of a turn at a time. The idle screws on mine are conveniently cross-marked. Give it a few revs between each adjustment and let it settle... patience required!

[Pete Lewis]

I echo  dereks plan

[leon.halliwell]

Thanks I’ll have a go and see what happens

[sulzerman]

Hi 

Make sure you turn both screws exactly the same amount,  or else you will upset the balance of the carbs 

[Pete Lewis]

For future twiddling, the balance is setting the idle air flow to be equal on each carb

You can use a proprietry tool quite cheap to measure the flow , you can diy a cover with tube and make a U tube manometer 

Filled with water  , or do what triumph did on supplies to the line ,  gas flowed settings were only developed when emmission controls took hold late in the 70s

Thats in simple terms a mechanical throttle setting, undo the idle screw so the throttle plates are fully closed, turn the screw in to just toich its cast stop, turn it in 1.5 turns    this will be as close to good as you can get when other means are unobtainium.

There is  some free slack travel on the interconnecting rod , the small levers on this rod need to be set to opertate the throttles equally

For this you undo the small clamp bolt and turn the lever on its shaft so both ends work together

This free travel is there so when using the choke the fast idle cam doesnt have to pull  the whole throttle linkages, the fast idle cam is also 

adjustable it has a small dome headed  tappet bolt there must be a gap between this and its cam when choke is in

If adjustment is needed the  fast idle on choke needs to be around 1500 rpm 

So realy no special tools required just a little observation and care 

Pete

[DerekS]

I echo Pete's plan... 

(there's an echo in here!)

[Pete Lewis]

 think its catching   ha !

the trouble is writing about something quite simple makes it extraordinarily lengthy  more  Ha!

Pete

[leon.halliwell]

Pete you need to create some sort of video library of your vast knowledge!

[DerekS]

I echo that plan... 

Sorry, I'll get my coat.

[dougbgt6]

Leon,

Last year Pete organised Twiddle Day at TSSC HQ. A great event demonstrating all sorts of methods and techniques on the cars of the people who attended. Well worth signing up for Twiddle Day 2 whenever it happens.

Doug

[Pete Lewis]

It will be when the suns up  dreaming of maytime for day 2

The last video I made is now on youtube look up RB44 production video  I had hair then but it doesnt get in shot

Myself Ray and Garth tried  to develope a how to video but the time required to cover all servicing aspect would have taken a liftime to 

complete and we dropped the idea

Pete

[dougbgt6]

Pete,

Perhaps we could film Twiddle day 2? An epic adventure staring Pete and Ray? 

A long long time ago in a galaxy far far away...............Pete Skywalker and his trusty crew battle against the dark side to save the Millennium Spitfire.

Could we get Ray into a Wookiee suit do you think?

Doug

[leon.halliwell]

Well when twiddle day 2 arrives sign me up! Not sure my spit will make it all the way up north! (North is anywhere past the M4) might have to ride the Kia bus

[Pete Lewis]

I will ask Ray but response may exceed the forum rules

Keep, an eye open form a twiddle 2 date all are welcome

It will be anounced in the forum and the courier magazine

Pete

[dougbgt6]

As an attendee of Twiddle Day 1, am I allowed a place on Twiddle Day 2?  Alzheimer's being what it is I've forgotten it all, so it'll be all new!  And I do want to see Pete in his red PVC jump suit.

Doug

[Pete Lewis]

see latest post in general  twiddle day2  set for MAY 20th  at HQ  10am 

come and join us 

Doug do you want B&B   ???

Pete