Weber idle jet O-ring?

206aa · 12-22-2003, 02:29 PM

Hi,

Forgive me if this is a stupid question. I have rebuilt my webers (40 IDAs) on the 68 911 that I purchased approximatley a year ago. I am having trouble getting the mixture set. While cruising through other posts I noticed someone made reference to an O-ring around the idle jets.

The carbs did not have o-rings installed around the idle jets when I started the rebuild, the only o-rings present where on the air/mixture screws. Do I need to have o-rings around the idle jets? If so, that would probably explain why I am having a bit of difficulty setting the mixture screws at 1200 rpms.

Thanks
________________________________
206aa
1968 Porsche 911 (2.4T)

cegerer · cegerer's Garage

There are definitely O-rings around the idle jets. Not sure how the lack of same would affect the mixture screws though.

rickeolis · 12-22-2003, 02:37 PM

I wish I had the legend that came with this, but here you will see #37 which is a rubber O-ring, which gets covered into place by the next item #36; this is a concave cap which the spring pushes against. Pelican's rebuild kit has the new O-ring's in it, but not the caps or springs.

Hope this helps some-

dhoward · dhoward's Garage

Number 37 goes around the mixture screws. I had the same question as I have to blow dirt out of my idle jets every so often (gotta get those PMO fuel bars and filters!). The drawing I had from Rennlist was very poor, and I didn't see a washer on the idle jet holder (which I think 206aa was referring to) Looks like #25 on your drawing. My guess is not o-rings, but fiber washers?

206aa · 12-22-2003, 03:05 PM

Rickeolis,

Thanks for the reply! Great picture by the way, most I have seen aren't as clear as yours. I was talking about the idle jets not the air mixture screws. So my question would be, is #25 rubber or brass?

I thought I had read somewhere that if air is making it in around the idle jets then it would be difficult to tune. I have rubber o-rings installed for #37. Perhaps they are the wrong size and air is coming in there? Anyway, turning the air mixture screws in , makes little difference until they are almost all the way in. . Does this make sense at all? Thanks for the help!

206AA

206aa · 12-22-2003, 03:06 PM

From dhowards post: "Looks like #25 on your drawing. My guess is not o-rings, but fiber washers?"

This is exactly what I was referring to. Fiber eh?

206aa · 12-22-2003, 11:34 PM

Thanks to everyone who replied. I think I am going to try the rubber o-rings and see if they help. .

Steve@Rennsport · 12-23-2003, 12:14 AM

Ohhhh, yessss,..they WILL help a lot.

One cannot adjust idle mixture on these carbs without these rubber O-rings on each idle jet holder.

Wayne 962 · Wayne 962's Garage

There is a pic and legend in "101 Projects" of this carb...

-Wayne

dhoward · dhoward's Garage

The pages in my "101 projects" are all stuck together.....

rs911t · 12-23-2003, 05:39 AM

YES you need rubber O-rings on the idle jets and you won't find them in any of the pictures (at least, the one's I've seen). Go down to your local auto parts store and get 008 o-rings.

206aa · 12-30-2003, 12:10 PM

Interestingly enough, the illustration in "101 Projects. ." doesn't show an O-ring, or any type of washer for that matter. The above picture definetly does show something. Anyway, hopefully installing the O-ring as Greg suggested will remedy the problem and I will be able to set the mixture. If not, it might be time to drop it off with John Walker

Thanks
Alan

206AA
1968 Porsche 911 2.4T

rs911t · 12-30-2003, 04:45 PM

All of the diagrams I've seen fail to show this o-ring.

cegerer · cegerer's Garage

Beyond the mixture issue, I don't see how you can seal the idle jet holder against leakage of fuel without the O-ring???? It would be just brass against brass. I've mistakenly left the O-ring off of a holder in the past and it leaked!

john walker's workshop · 12-30-2003, 05:21 PM

they'll still seep over time. every carb you see has red seepage marks around the gaskets, jets and plugs.

206aa · 01-02-2004, 04:39 PM

I installed rubber o-rings around the idle jet holders and replaced the main jets (with 130's, the previous jets were tiny in comparison with no size stamped on them!). The o-rings seemed to have made the mixture easier to set or maybe I have finally developed an ear for it, beats me . . Anyway, after installing the correct main jets, correct idle jets (with o-rings) and oiling the o-rings on the mixture screws. . . My webers are finally tuned and the car purrs. It is really nice to have seamless transistion between the idle and main circuits now, what a difference!. . My 2.4t weber setup is as follows:

Main Jets-130
Idle-.55
Venturi-30
F26 Emulsion Tubers
Air Correction jets-180

This seems to be a winning combination so far. .

Thanks to everyone that replied and to all of those who have contributed to my weber tuning education

--Alan

206AA
1968 911 Targa (2.4T w/webers)i