engine and drivetrain 40DCOE help

[minicoop900]

yes, i did search, found most of what i was looking for but im still confused as to what i should re-jet them to.

engine specs:

stock head,block

stahl headers, aftermarket sport midsection and muffler

any help is appreciated.

im also looking for an electronic ignition if anyone has one lying around

thanks, logan

[02for2]

Pat Braden's book on Webers suggests the following for the 2.0L 2002:

Venturis - 33mm, aux. ven. - 45.0, emulsion tube - F16, Main jets - 120, Air correction - 190, idle jet - 0.50 (F8), pump jet - 0.40, needle valve - 175.

This is a good start, but to really dial in your individual motor, I'd go up/down 1 of each main and idle jets and see which works best.

Also, this assumes the engine is in good tune - valve lash, advance, ignition, no air/vac leaks, floats properly set.

If you haven't done this yet, you're in for an excercise in frustration.

Do the fundamentals and then fine tune the carb.

Cheers!

[TobyB]

I'd go fatter than that- maybe 130 main, 170 air. 50 progression's right on.

You can't get 33 chokes easily- I'd go down to 32's

But 02's exactly right- you pick a start point, then go from there.

t

[AlanM]

What jets and tubes do you already have? Don't get too fixated on the venturi size 32 or 34mm will be OK, 50F8 idle is a good place to start.

F9,15 or 16 will most likely work as emulsion tubes. Don't be too quick to buy different ones as they are expensive. And as above 130 main with 170-180 airs is a place to start. Each motor is a little different.

[TobyB]

Sure- if you have a set of 34's, use them.

But if you have none (or have 36's)

go smaller.

The thing is, the larger the venturi (choke) the better the

carb flows.

But the worse it meters fuel.

So a set of 36mm chokes in 40mm carbs

will be hard to tune well at cruise and for moderate acceleration.

You'll get more wide open throttle power- but at the expense of

bad manners in town and on the freeway. The progression circuit will

have to do most of the work, and it's not really very well adapted to

do that.

With a big choke, the main jets 'turn on' a lot later, as fuel's not

drawn through them as soon.

But a set of 30's or 32's will generate lots of vacuum 'signal' early on,

so you'll be able to tune the main jets for

smaller throttle openings. And the main jets will flow fuel sooner, so

you'll be less reliant on the inefficient progressions.

Carbs are really mechanical computers- if you mess up the

'input conversion' part, they don't give very useful output.

Make sense, sorta?

t