Weber strange idling settings

[BartdeBruijn]

Hi,

I completely lost it.......

- Porsche 911 2.0T 1969
- Engine completely rebuild with some mods ( no power increase)
- Before rebuild engine was running relatively fine but many oil leaks
- Webers (40 IDTP)are been taken apart completely cleaned and rebuild (throttle shafts have 'some' play car was running fine with them)
- carbs are 100% original)
Fuel pump is old
Float heights are set NOT while car is running ( took me long to get it running idle)
- distributor has been rebuild and tested by professional German company
- new spark plugs correct electrode gap

I followed the basic carburetor setup described in the great "essay" by Paul Abbott!
When I Start the car I have to nurse the pedal for a while and then I can find a steady idle around 1000 rpms using the hand throttle (beside handbrake). At this steady idle it (almost) doesn't spit through intake.

Now the strange thing is that my STE synchro meter measures around 10(kg/h)!!! At +/- 1000 rpms. See pictures.
One picture shows how far the hand gas handle opens the throttle valves, the other shows how much air is been sucked in.....
What I remember is that 5 kg/h @ 1000 rpms is normal.
Not all exhaust pipes seem to have the same temperature.....

Does anyone has a clue what is wrong here's?
I am running out of ideas.
Maybe Paul Abbott or another Weber guru can help

Hope someone can help to get me on the road after a 18 years full car restoration ;-))
Regards,
Bart

[1QuickS]

Check out responses on Early 911S Registry forum: Weber strange idling settings

[BartdeBruijn]

Thread also running on early911sregistry......driving me nuts so try to find the answer(s) solving issue ;-)

Dear Weber and engine gurus

I am still struggling with the carbs.......

As you know I did the following since the last emails:
- checked hidden galleries -> were open/free (air came out of auxilairy venturi holes
- checked float level with PMO-tool ( exact between two lines)
- set static timing ( as a starting point ;-) running at +/- 1000 rpm @ 5* ATDC
- measured compression (cold) all between 130 & 135 psi
- distributor marelli has been restored and curve checked at specialised German company
- new spark plugs (checked spark plugs in lawn mower ;-)
- new spark cable/leads
- checked resistance all the same
- Someone on early 911 registry mentioned to have the right cam shaft timed wrong.....? For me unclear what he means as car is running!?
- carbs are 100% standard (Italian) Webers 40idtp that (before cleaning etc. we're functioning ok.
- I am still using my old fuel pump....!?

So where are we now:

- situation is still as earlier pictures in thread. Throttle plates are still so far open that that progression holes are free. In this situation engine revs +/- 1000 rams and uni sync reads almost 10. Right weber bank spits almost constantly! Exhaust pipes all reach more or less same temperature however could also be due to nursing the throttle. Engine seems to rev ok when nursing throttle.

- I mounted 3 colortune plugs on right bank (cyl. 4, 5, 6) -> difficult to check, but see sparks and almost no blue / orange when I push the throttle I see some yellow colour due to rich (accelerator pump) mixture.
- I can turn in mixture screw on right bank all in without any effect.
- mixture screws on left bank have effect -> Rpms go down
- also sprayed carb cleaner in right bank weber intakes without any effect

Could it be timing cam shaft right side ?

I am slowly pretty much out of options......

So anyone? Would be very appreciated because it is starting me nuts!

Best regards,
Bart

[Steve@Rennsport]

Bart,

Tough situation to resolve on internet forums due to the sheer number of variables!

Naturally, your cam timing and valve adjustments must all be spot-on and all the same.

Further, there can be NO air/vacuum leaks between the heads, manifolds, carbs, and throttle shafts. ANY,...any false air will result in these very issues.

Fuel pressure must be 3.5 psi and the floats adjusted so they are all perfectly identical (this takes time & lots of patience to do).

Once this is all done and confirmed, look at Paul's page for setup instructions as this is the next step: do NOT assume anything!!

Good luck!

[BartdeBruijn]

Hi Steve,
Thanks for quick reply!
The engine is the last part on a 17 year restoration project..... So it's about time ;-)
There is some play in throttle shafts but using carb cleaner near shaft, manifolds etc and in ventures gave no rise in Rpms..

I did all engine myself including timing, checked it several times and was then surprised that I was lucky that I got it second time right..... I thought....
Is there a (quick) way checking cam timing with engine in the car?

Could be wrong cam timing of the right cam be the cause of these strange idle settings(see pics)

Cheers,
Bart
From the Lowlands

[Steve@Rennsport]

Originally Posted by BartdeBruijn

Hi Steve,
Thanks for quick reply!
The engine is the last part on a 17 year restoration project..... So it's about time ;-)
There is some play in throttle shafts but using carb cleaner near shaft, manifolds etc and in ventures gave no rise in Rpms..

I did all engine myself including timing, checked it several times and was then surprised that I was lucky that I got it second time right..... I thought....
Is there a (quick) way checking cam timing with engine in the car?

Could be wrong cam timing of the right cam be the cause of these strange idle settings(see pics)

Cheers,
Bart
From the Lowlands

Hi Bart,

Assuming there are no vacuum leaks for the moment, cam timing differences create differences in intake manifold vacuum. This alters idle jetting and carb adjustments.

If the differences are big enough, you may not be able to get the engine to idle properly since you may be out of range of adjustments.

You can check & adjust cam timing in the car, however the muffler, rear tin and rear engine crossbar need to be removed to gain access. Naturally, the upper valve covers and chain covers need removal as well.

Its also possible there are still some obstructed passages in the idle passages so I would investigate that first.

Hope this helps,

[Heinz911]

Bart,
Carburetors for me are like Black Magic, so best to seek a magician. I have very good experience with BAS in Lichtenvoorden. I don't know where you live but for me it is a 2 hrs drive worth while.
Groeten, Jasper

[turbo nut]

If the engine is only running on one side and you think you may have the cams timed incorrectly switch the plug wires in the cap and see if it runs on the other side.