Carby Jetting

[Talasas]

Okay, let's talk carby jetting:

I have here an as new Weber 32/36 DGAV set to go on a Datsun A12 engine. What I'm curious is, I don't understand when I need to change the jets and/or how the size of suitable jets are worked out.

I know it's something based on engine capacity and performance, but is there a direct formula to calculate jet sizing?

So in this case it's a stock 1200cc Datsun engine, and the carby is running some jets of unknown value x (I don't have it with me where I am atm)

So how can I work out what is suitable to use for this engine?
I'm a little new to carbies still but am dying to learn...

Experience welcomed

[Screamn_Sleeka]

www.datsun1200.com

Use that site to find out what people are getting decent results with.

Then you need dyno time to perfect it.

To change there sizes, use a soldering iron to fill the whole then drill them out to the new size. Buy a pack of micro drill bits and a hand drill (its like a pen but metal and takes drill bits). These kinds of drill bits are all junk in australia, google search usa site, you can have good quality stuff delivered to your door for under $10.

Make sure you measure the bits with verniers before you use them, cheap ones are always off.

[Talasas]

Thanks mate, but I'm already a member there.

I'm just more curious at how people know what jet sizes to change them to, by the looks of all the reasearch I've done that it is mostly guesswork and experience.

Anyway we'll see how it goes, I got my hands on some reccomended baseline setups.

[MWP]

... that it is mostly guesswork and experience.

Yup and yup.

Every engine behaves differently due to different VE's.
Cams, chamber, intake, exst, etc, etc, all change what jetting is required.
So there is no formula by engine capacity.
You can guess, but itll always need to be tuned properly on a dyno to get the most out of the engine.

I did mine by feel only and it worked out ok. Took a long time though, a few months of tweaking now and then.
Has a little dead spot at the end of the first throttle, but is quite good considering...

[Talasas]

Hmm interesting. Well at this point we are putting a pause on the Weber as all the bits needed to convert to EFI have come up so we might make the most of the chance.

Anyone interested in an as new 32/36 DGAV?