weber jetting 40-IDA

[206aa]

hi,

I have a 2.4t running weber 40 IDA's. The idle jets are .50. I have been experiencing an irregular idle and the transition from the idle circuit is a little sloppy. This is after a complete rebuild on the webers, valve adjustment and carb synch. Oh yeah, new alternator and fuel pump as well (seperate issue). . .So I figured that perhaps the idle jets are too smalll and should be bumped up to .55.

So now the interesting part. I started on a hunt for idle jets and ran across a picture of what the 40 IDA idle jets look like. They don't look like mine. Mine look like IDF idle jets. Is this possible? Could I be using IDF idle jets? If so, does it matter?

Also, any recommendations on where to purchase idle jets? I don't think our host carries them.



Thanks,
Alan

arringto
1968 911 Targa (2.4T)

[Tyson Schmidt]

Before you do anything else, pull the fuel level sender out of the tank, and shine a flashlight down into the bottom. Check for rust. Also remove the fuel filter and blow through iut backwards into a white rag. If you have fuel contamination, you'll just drive yourself crazy trying to tune the carbs.

The rust will actually make it past even th finest filter, as it is a very fine dust. Then, it will rust together in the float bowl and form larger particles that will then clog the jets.

[206aa]

Been there and done that. Thanks for the suggestion though Tyson, it is good advice.

-Alan

[cegerer]

For reference, I'm running 55's on my 2.5L.

Here's some parts sources:

Weber Carb Websites

[206aa]

Excellent, thanks for the parts sources. I just ordered the 55's from Pierce Manifold. I read a post from John Walker recommending 55's due to the changes in gas over the years. .

So, it couldn't hurt

--Alan


Arringto
1968 911 Targa (2.4T)

[Tyson Schmidt]

When I had Webers on my 2.4 T with 10/1 CR, I ran 32mm venturi's, 1.35 mains 1.80 air correctors, and .55 idle jets, and F1 emulsion tubes. Ran damn near perfect.

[206aa]

thanks guys, I will let you know how it goes. The jets should be here in two days.. .

--Alan
______________________________
206aa
1968 911 Taraga (2.4t)

[obrut]

I took the easy route - faxed PMO will ALL my major engine specs and Richard sent me his recommendation for street and street/race jettings. Went with the latter, ordered the bits from him, car was transformed.

Cheers - Ryan

[Rich911E]

Ditto to Ryan's post -- ask PMO. They will give you good recommendations and can supply the parts. Their recommendations worked perfectly on my car.

You didn't mention what the plugs look like?

If the idle is funky make sure the carbs are balanced perfectly from right to left with all the linkages disconnected. Then make sure you don't disturb the balance when you reconnect the linkage (very easy to do).

Regarding the transition problem, did you evaluate the volume of the accelerator pump shot? If you are getting too much fuel from the accelerator pump on throttle application, it will cause a bog.

I have a really good tuning procedure that was posted earlier on this site. e-mail for a copy.

Rich

[arringto]

This is all happening after a complete rebuild,balancing and tuning of the webers. I noticed tonight that there is a little bit black smoke when you crack the throttle. . Too rich? Or could this be timing/point gap? I plan on checking the timing and gap tomorrow. . . Hopefully I can test accelerator pump volume tomorrow as well. .

Ordered some 55 size idle jets. . Thanks for the help guys.


Alan

206aa
1968 911 Targa (2.4t)

[Rich911E]

A little black smoke when you hit the gas -- sounds like a bit too rich. Is it just a puff or does it stay for a while?

First, pull the plugs and see how it is running. There must be a color photographic spark plug reading guide somewhere on the internet. Champion used to publish one. Check your plugs against that. Are the plugs on the right cylinder bank similar to the left cylinder bank. If the carbs are not balanced, one side may be sooty while the other side are OK.

It sounds like you had somebody do the carburetors? Is that correct? Once upon a time I had a "expert" set my carbs which were so wacked out when I got it back that I just did it myself. This board provided a great tuning procedure that has worked well and has worked for others besides me. I can send it to you if you send me an e-mail (too big by PM).

Rich

[206aa]

Black smoke stays for while. It also puffs a little white smoke at startup. It seems like it is running rich. I just checked the timing, dwell and point gap. They all seem correct. I rebuilt the carbs myself with proper float levels, I have had them apart atleast twice double checking things here and there. I also went through tuning them with side to side balance. . Maybe I just need to start from scratch.

I still need to do the following:

*Pull the plugs and have a look
*check acclerator pump volume.

I'm puzzled to say the least

Rich,
Are those the same directions posted by T-Bird (John)? If so, I already have them. If not, I am always up for new instructions/ideas. .


Thanks
Alan

__________________________________________________ ______
206aa
1968 911 Targa (2.4t)



Thanks for the help guys.

--Alan

[206aa]

Also, one other somewhat related question. If I am not going to use the vacuum advance on the distributor, do I need to plug it?


-Alan


__________________________________________________ _______
206aa
1968 911 Targa (2.4t)

[rickeolis]

You obviously need to plug the end coming from the engine, but the end on the dizzy should simply be covered to keep dust out.

[206aa]

I checked the fuel pump volume, it pumps over a pint in 30 seconds. Not too much more though. I installed the idle jets (.55) (2.4T) that seemed to help the low end but there is a dead spot when it transistion off the idle circuit followed by some popping in the exhaust. Car kind of bogs after that.

I checked the float levels. They are off, using the PMO tool it shows beneath the top two lines but over the bottom two. Could this be the problem?

Thanks,
Alan

206AA
1968 911 Targa (2.4T)