1965 200ci Mustang: Weber carburetor jetting

Hello everybody,

I'm a new french forumer. I'm here to have help, and I don't find answer to my question in France....  

I'm going to put a Weber 38 DGAS synchronous on my 65 L6 Mustang. I'll have 2 carbs, but anyone has jets...

So I would like to now what jet size (main, idle, and air corrector) I have to put into my carb to work well with my engine.

My inline 6 is equiped with a MU BA55 header, a Comp Cam SK-KIT HIGH ENERGY 252H, and a home made stainless steel dual exhaust with CherryBomb glasspack.

I've a Petronix ignitor I too...

Dual exhaust with glasspack sound

Thanks a lot.  

just curious...

weber DGAS...  2 barrel...   there are weber jets available all over the web...   i have tinkered with weber carbs over the years...

are you running a single 2 barrel carb.. or 2  two barrel carbs.. that i am confused about..

you are going to want to search out a really good book on weber carb tuning..

a few things...   i have little info on the 38 DGAS... is that a progressive carb.. or is it a 1 to 1 opening ratio carb.. as i can see a quarter gear to open the secondaries..?????/

you are probably going to want to invest in a air fuel ratio display..    an oxygen sensor bung installed in the header collectors..   depending on the collector flange size..  there are a few spacers for the collector to exhaust pipe to allow an oxygen sensor without damaging your collectors..

lets talk about idle jets..

idle jets screw into the side of the carb.. easily changed..

if your idle mixture screws are too far out..  and its still too lean at idle.. you need to go larger.. ONE size at a time... sizing on this model idle jet  is 40 to 80..    so.. if you back the idle screw all the way out and its still too lean.. step up one size..

if the idle mixture screw in almost seated...  the idle jet it too large...    

i am recalling that the idle mixture screw should be out about 2 .5 to 3 turns..  

the idle mixture is adjusted by the screw..  the idle jet... controls how much fuel is pulled into the idle circuit..  

what is NOT written... is the idle jet is the IDLE FEED RESTRICTION for the IDLE TRANSITION SLOT..  this is where you are going to get your incredible fuel economy or NOT..  if it has a nice transition off idle.. or not..  

the idle mixture screw limits the fuel being pulled in below the closed throttle blade...

the idle jet limits the amount of fuel pulled through the idle transition port/slot just above the closed throttle plate.. when its in transition from fully closed to part throttle and air flow is enough to pull fuel over the booster venturis..

all this and you get to about 2500 RPMs...

anything above that is on the main jets.. the air correction jets.. and the emulsion tubes...

the idea is to buy a bins of the various idle jets..  air correction jets.. main jets..   even a few sizes of accelerator pump discharge nozzles..

its a shame that dynos are so expensive..  and that carb calibration parts are so expensive . but the payback if you get it right is worth it..

i don't personally like to do WOT tuning.. until i get the idle tuned.. then the idle transition verified..   then the mains... with fine tuning done with main jets and air correction jets...  

Thx for all these explanations!!!

So I don't want to install 2 two barrel carbs. Only one is enough...

I just want to say that somebody will give me 2 carbs, but none as jets, they're uncomplete.

The 38/38DGAS carbu isn't a progressive but synchronous carb (HERE a pic), with as you said a quarter gear to open secondaries.

What's WOT tuning?

I found docs about Weber setting in french. It seems to be hard... I won today on ebay a complete 38/38 DGAS carb in good condition, I think I'll try to see if it my engine runs well with. I'll keep others as parts donors...  

all the jets removed... OHHH!!!

hopefully the ebay version will be complete...

please..   take it apart with  care...  write down the various jetting numbers... so you know a base tuning..

i am taking that you have some kind of adaptor to go to the single opening in the ford head casting..


What's WOT tuning?

Wide Open Throttle...   full power...  this is calibrated with the main jets... and air bleeds...  mostly main jets..

so ..please make a list...

please..  start at idle tuning..   then off idle...   then the low speed tuning..  then go to the high speed..

since you have a synchronous carb.. the jetting should be close to the same for both primary and secondary..
idle jet #..

air correction jet#

emulsion tube#

main jet numbers...

hopefully all the other small parts will be there.. and not stripped out..    there are PDF diagrams online..   print one out.. so you can verify the parts..

i don't know personally of any written down tuning specs for jetting.. but i bet they are out there in the hands of weber carb techs..

i have a question..     what are your plans for this car..    street driving or drag racing??  rally racing..

why did you select a synchronous carb rather than one of their progressive carbs...

even something downdraft from SU or . perhaps solex...  or even one of the 34MM weber single barrel carbs..  

Ok, so I must make adjustments step by step...From idle to high speed...

I've got diagrams, I found them.

Plans for this car? Daily driver, with a little beat more power than stock, sometimes drive on a circuit... Have a mixed-use car.

1/ Why a Weber... Many classic Mustangs owner do that conversion from 1V to 2V with Weber... I said me "why not". lol.
2/ Why a synchronous and no progressive... I still have a progressive, that's not bad, and I want to see if synchronus is better or no... It seems that 38/38 synchronous is a good upgrade for 32/36 progressive... As we say, wait (try) and see...
3/ Why a two 38 and not a single 34... Stock autolite 1100 carb is a 36mm single barrel... Upgrade carb (for me) has larger butterfly, 32/36 is a good upgrade with some modif. on engine, 38/38 is better when engine is more prepared (it appears)...

As I said, I had 32/36 progressive, that was better that stock one barrel. So I'll go to see if with 38/38 that will be better...

I'll tell to you what's better, which improvements it brings (or doesn't brings)

Thx for your interest & see you soon