Hello Everyone!
I've been reading around for a while and have decided what carb jets to order but i still have a few questions.

My current setup on the carb as I bought it is:

Main Jets: 185
Air Correctors: 180
Idle Jets: 70
Emulsion Tubes: F7
Needle and Seat: 200
Chokes: 42mm

What I plan to buy is


Main Jets: 190
Air Correctors: 150
Idle Jets: 65
Chokes: 40mm

This would leave the F7 emulsion tubes and the 200 n/s (is that ok?)

I am not too sure about changing the Pump Jets but if it will get my car running better I'm not opposed to it. Anything to get it not to idle at 3k rpm lol.
The filter under the banjo bolt is gone and I installed a big carter fuel pump.

Do you think that will be a good setup for a stock 12a with a full exhaust?
I daily it in the summer.

Thank you in advance!

 

i would try to find a larger needle and seat, we're all running a 3mm or bigger. keep the F7 for now, its the correct one for a 12A.

for the jets, you really need to see what the AFR's are on your engine, the carb works based on airflow, and airflow changes with the engine/exhaust. so its not really possible to say that changing from a 70 idle jet to a 65 idle jet will do X to the AFR.

if you want an example, i have the same carb on my P port 12A, and i'm running the same fuel jets as you are, and how is that possible unless the carb responds differently.

 

So do you think the jets Im gonna buy will be a good start? Ill order a 300 N/S along with them too.
How do i check the AFR?
Thanks again!

 

most of us are using a wideband oxygen sensor to find AFR's, although since the carb is a little simpler, you can tune without it.

i should ask, what problem are you trying to solve by rejetting the carb? as a note it is important to go through the carb in a logical sequence, you must always start from idle and work your way up, due to the way parts interact, if you take a short cut you can easily end up totally lost.

a high idle can really be only a couple of things. basically too much air is getting into the engine, either its a vacuum leak, or the throttle isn't closed, or the throttle shaft seals are bad. closing the throttle is pretty easy, back off the throttle stop screw, mistakenly known as the idle speed screw until it doesn't touch the throttle arm. screw it in, until it touches, and then turn it 1 more turn. set the idle mixture screws out 1 turn from seated. start the car and see how it runs. idle should be ~1000rpm, give or take. adjust the idle mixture screws, in a perfect world they should end up between 1/2 turn from seated and a full turn from seated. if your car idles best with these all the way in, then you need a smaller idle jet. if it is further out then you need a larger idle jet. you just tune this where it runs the best, although you could hook up a vacuum gauge and tune it for the highest vacuum too.

if its idling way too high or way too low, look for vacuum leaks. i use carb cleaner, but propane works.

once you've got it idling, find a space of road or parking lot thats flat and without traffic. then pull the main jet stack out, and go for a drive. the idle jet will only supply fuel from idle to about 25% throttle, so the car will be really slow. try a couple of idle jets, you want the best driving one, or maybe the next smallest. again this one is a runs the best, if you had a wideband, you would be shooting for around 14:1 here, give or take.

then you can put the main stack in, and go for a drive. with the main stack the fuel jet controls how much fuel is delivered, and the air controls when its delivered. the test for the when part is to run the car in 4th, at an rpm where the idle jet works (depends, but ~1800ish) and floor it. if the air is correct the car will just go. if it goes, and then stops running, its too lean. if it goes and then bogs, its too rich. too lean needs a smaller air, too rich needs a larger one.

the how much, is the AFR, and without the wideband you need a stop watch or something, and go from the biggest jet you have, which ideally means the car doesn't run, to the point where its the fastest, and then you want to go a jet or two richer. method B is to get it so rich it doesn't run, and then the next leanest where it does run. max power AFR is somewhere between 12.5:1 and about 13:1. leaner gets a little dangerous, we want a little margin for a really cold day (cold air is more dense, more dense = more oxygen and more oxygen = more power). richer is fine, you will start to loose a little power.

 

Ok thanks man! ill try that out once it is a little later in the year as my car wont be insured until then! Should i order jets so i have them or not even worry until i have the time to test?

 

you can start just in the driveway/garage. i wouldn't order jets until you've at least done the first round of testing either, its hard to estimate what you'll need, and buying all of them get $$$