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-   -   several 55 idle jets available whats the diff? (https://www.rx7club.com/race-car-tech-103/several-55-idle-jets-available-whats-diff-382737/)

xrotaryguy 01-05-05 01:48 AM

several 55 idle jets available whats the diff?
I was just looking at buying some different idle jets and I see now that there are 3 noy 4 different kinds of jets if i want to buy a 55. Theres a F12 F8 F9 and an F2. What the heck is the difference? Will they all fit in my carb? Im using a weber 48 dco by the way. And what does this F this and F that stuff stand for. And is there a F U size as well? Sorry, I oculdnt help myself from that one. Lol gravy!

Also my carb is acting very badly. It makes good noises between 3500 and 5 grand with my foot flat to the floor. but thats the only time it sounds good. it wont idle below like1800 and even then i have to keep clearing it out. and at any kind of part throttle it sounds really crappy just missing all over the place. I know.... thats not much to go on. I dont know what all the jet sizes are in this thing. Its a street ported 4 port 13b with a rb header lake citiy rotaries intake. The mains are a 200. I'll have to look at the rest. Are there marks on the jets to tell you which one is which or do i have to memorize whats in the carb all the time?

Tom93R1 01-05-05 11:39 AM

The jets all have a mark on them, so when you pull the jets apart you will know.
When you stop by tonight we will see what is in my truck right now and what was in it when you had the carb, compare that to what is in yours now and maybe that will tell us why it is running so bad.

I would let you take all my jets so you can have a few more to experiment with but my FD just started leaking coolant so the REPU is my primary transportation the next couple days. This weekend though if I get the leak fixed you are welcome to all the jets.

I did find something very much worth remembering regarding the air corrector jets, since we were talking a bit about them the other day.

For a given air correction jet, a larger main jet will flow more fuel across the RPM range.

For a given main jet, a larger air correction jet will reduce fuel flow in the higher RPM range
That came from http://www.teglerizer.com/dcoe/webertune.htm
Looks to be some good info in there.

xrotaryguy 01-06-05 11:32 PM

Ok well I figured out why my carb ran so bad before but now im still not happy with it by any means. with a 55 idle jet it runs very nice at idle, hesitates when slammed to full throttle and pulls unimpressively at full throttle before starting to miss fire towards the upper end. With a HUGE!!! (we're talkin drilled out to like 1/32 or 1/16 of and inche here) it idles horible and i have to keep flooring it to clear the plugs and even then it takes many attempts to get it running on both rotors again. but it has excellent throttle response (when its not flooded) and pulls like a raped ape to 6500 where it is still pulling hard but i dont wanna push my car too hard. This is with the idle mixture screws out only like a turn and a quarter. So I need a bigger idle jet. like a 65 or somethign. but what do i do with the "F" number? What does that number mean? Does any one here know?

cpa7man 01-07-05 07:32 AM

Good information here http://members.aol.com/dvandrews/webers.htm .

I started a thread on this in the 1st gen section that is still a work in progress. It would be good to get all the data in one thread. Engine & port's, carb type & size, emulsion tube, air correctors, main jets, idle jets and all details on the best setup.

The idle and transition from idle to mail jets occurs at around 3000 rpm I believe. So any stumble is caused by the wrong idle jets and/or accellerater pump size. After that it's all et's, ac's and mains. Some have posted that the in carb filter needs to be removed to allow more fuel flow. Also an in line fuel pressure regulator is important.

xrotaryguy 01-07-05 10:43 AM

I'll look at that one

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