Weber's Affair

[C J Murray]

I think the O2 sensor should be put away for a while. I do not think you are staying within the range of jetting that is likely to work and I suspect that the meter is just confusing the issue. For instance, when jetting gets very rich the meter will read very lean and confuse most people. If you did not know this you are not alone so put it away until you have the car running very well.

Idle jet...with a 50, does it idle best with the mixture screw not far from 1 turn out? Does the car run smoothly driving on a flat surface at a steady throttle position at near 2000rpm? Yes, yes? You have the right idle jet and you should leave it alone. DO NOT USE AN IDLE JET TO FILL IN A FLAT SPOT. Leave it alone!

Air jet...start with a 200 with a 135 main(likely to be too large main). Flat spot 2000rpm or a bit higher? Keep going larger with the air jet until the flat spot goes away. It may seem very good at this point but avoid extended wide open throttle in top gear.

Main jet...with the air jet chosen you can start reducing the size of the main jet to see if that improves the running of the car. If the first move makes the car run worse then start going up in main sizes until it runs best. The objective is to use the smallest main jet that drives well.

Now hook up the O2 meter and test the mixture reading at wide open throttle in 3rd gear to hopefully confirm a mixture near 12.8.

[Joao Filipe]

Hello Craig,
Thank you for your post. Nice to have you both in Portugal at 39th International Porsche 356 Meeting, 2014 (1). Maybe I have found you here (2), right? We were there (3) too, me and my good friend Heick in his 356 C, 1964. Very nice memories, indeed! Congratulations for your “How to make them fly” that I true appreciate. I read careful the Weber’s chapter and your current remarks. I’m quite sure the engine has his original camshaft so your previous advices about the bigger idle jets may be still okay. I will pay attention to that too. F11 or F3 (?) - I try both with 200 correction air and they seems to me very similar. I Know that someone in the Registry with a S90 use 225 correction air “to get the mains to kick in sooner” as you say in your post (and 64 idle jet – but has a no stock web-cam…). Glad to know that is possible to eliminate lags or flat spots. But I’m not a tuner (in fact I’m a retired math teacher), so I will take my tiiime…
Thanks again for your answer and for the nice references to Portugal and to our International Porsche Meeting.

(1) https://www.youtube.com/watch?v=lsPBYlQUaFc
(2) https://abtfoto.smugmug.com/Cars/39-MEE ... 9/n-3x56L/
(3) https://abtfoto.smugmug.com/Other/39-ME ... 8/n-4cQc4/

[Craig Richter]

Joao,
That's our red Speedster in the back of your photo! Jose Guedes and his team were such charming and well-prepared hosts. Wonderful memories.
We hope to attend next year's meeting in Barcelona. My brother-in-law's '60 S90 is currently in restoration, so we'll have to wait and see if it's ready to ship in time. Hope to meet you there!

[Dave Wildrick]

I don't wish to undermine the advice of noteworthy folks like Cliff Murray and Craig Richter, but it's worth repeating John Willhoit's advice on setting up the Weber IDF40 (w/28mm venturis) for a stock engine with a stock cam:

[Subject: Re: To all you weber experts
From: John Willhoit <jbwillhoit@yahoo.com>
Date: Sun, 20 Jul 2003 16:09:55 -0700 (PDT)

[Hi Paul,

First step in adjusting would be to screw the idle
bypass valves closed (the little screw with a nut on
it next to the idle mixture screw). Next make sure the
throttle linkage is balanced (back off the idle stops
until the butterflys just close and check that the
adjustment from side to side on the throttle rods is
even). Open the idle stops about 1/2 turn, the idle
mixture screws 1.5 turns and start the car. Adjust the
idle equally on both sides to get it at about 1K rpm.
Screw the idle mixture screws in individually until
the idle starts to slow down then back them out about
1/2 turn.

That should adjust the carbs correctly. Before doing
the adjustment, I would recommend changing to the
following setup with Weber 40s: 28mm venturis, 115-120
mains, 175 ac, F7 e-tubes, 50 idle. If you have an
050, set the max timing to 36 degrees (about 10
degrees at idle). We have spent a lot of dyno time
with Webers and this will produce the best running
engine, especially with a stock exhaust With the
smaller venturis you will give away about 2 hp above
5200 but will gain torque and drivability up to that
point. If you still have a hesitation it could be a
characteristic of the cam. Norris cams use older
profiles which have a slower ramp and a lot of seat to
seat duration. You can help this by opening your
valve adjustment to .008/.0010".

Try it. If you're not happy I'll eat a bug.

John Willhoit]

I'm currently using this setup on both of my C coupes, with no complaints.
The only difference is that I am using the 123 ignition (from the Netherlands) instead of a Bosch distributor, although performance was also good using the Bosch 050 before I went to the 123 ignition.

[Craig Richter]

Hi Dave,
With all due respect to John's considerable expertise, and your own, I don't run stock motors or 28mm venturis. I still like my street 356's to... FLY. I wish I could someday give you a ride in Speedy, because he can actually beat those socker moms in their new KIA's...

[Joao Filipe]

Thank you all: C J Murray, Craig Richter and Dave Wildrick. I will be working hard on it almost all the time - waiting for a miracle. Merry Christmas!

[Joao Filipe]

Hello all, maybe I finally found one of those "magic jets combination" for Webers in this SC standard (?) engine - Goodbye “flat spot @ 2000 rpm”, hello nice and “linear performance” all the way (Craig).
Well I did not measure the consumption yet (high for sure or maybe not, but who cares for now (…) let me enjoy that feeling of being a “proud tuner” (Craig) for a while.
No, 28 venturi are not for me either, 32 sounds pretty right (Cliff) and cool in the SC. I was told that “problems with stumbles are caused by bad main circuit” and that we may need more air to clean up transition” (Cliff) or “210 even 220 air correction jets” to get the mains to kick sooner” (Craig).
Of course you are right and I’m quite happy with the results, thank you.
Why F3 instead of F11? They seems to be quite equivalents (except the body diameter that is smaller - Jeff Stevens) and the shape of the holes in the F3 seems to be conical (photo). Is it only a cosmetic finish?
As I was told to put the O2 sensor away for a while (Cliff) I did it, but I found an old “abgastester – bosch ett 008.03” in Netherlands and could not resist reading something instead. As the CO @ 1000 rpm was ok = 2.0% (in both sides) I felt better. Besides that 2.0% CO ≈13.8 AFR with Idle jets = 60 (!)
With so few kms done I cannot start reducing the main jets yet. The rain must stops first... (it’s Winter time) then I would like to put the LM-2 on board and read with a “wide open throttle in 3rd = 12.8” AFR for the mixture (Cliff).
After changing the “firmware” of LM-2 (Innovate Ingrid’s advice) it stopped rebooting “all the time” as it did before. Now it reads both AFR ok but the rpms are unreliable. Another setback but we are closer.
Joao

[Neil Bardsley]

I enjoy your weber adventure. How does your rpm/torque graph look now?

[C J Murray]

Joao, I am glad that the advice we all gave was useful. Carb settings are never "carved in stone" and there is more than one way to get good results.

Now you can evaluate your settings by driving under all types of conditions and you can also closely measure your fuel consumption. The very best tuning/jetting will result in easy starts, no popping from the carbs or exhaust, no stumbling, no surging, no pinging, and fuel consumption in the 28-32 miles per American gallon. If you have achieved that you must enjoy some quality beer or wine.

[Jeffrey Leeds]

Interesting to me, that Bruce Anderson , who spent a lot of time with the 356 and later 3.0 ltr. and 3.2 ltr. 911 engines while at Garretson's, settled on the F3 emulsion tube for 40 mm Webers also.

[Pascal Zundel]

For the record, my 356 with a 1720cc engine and Webers runs (or flies should I say) with John Willhoit recommended set-up.
If you have time to waste or plan to race, feel free to try your own tune-up.
If you don't and just want a great-running engine under normal road-going conditions go for John's recommendation.
My own advice (for whatever it's worth) would be to add a 123-ignition and your car will fly.
Cheers

[Dave Wildrick]

For the record, my 356 with a 1720cc engine and Webers runs (or flies should I say) with John Willhoit recommended set-up.
If you have time to waste or plan to race, feel free to try your own tune-up.
If you don't and just want a great-running engine under normal road-going conditions go for John's recommendation.
My own advice (for whatever it's worth) would be to add a 123-ignition and your car will fly.
Cheers

I agree with you totally with respect to the IDF40s with 28mm venturis (and that's the setup I use including the 123), but Mr. Filipe is using 32mm venturis, and the tuning situation may be different based on what Cliff Murray and others have posted.

[Joao Filipe]

Cliff, I still must wait for the fuel consumption and for the “Porto" wine too - it will do ok. Thanks.
Hello Jeffrey, maybe we need to get back to the subject: air correction jets. Thank you.
Hello Neilbardsley, thanks for your feedback about this “weber adventure”. Maybe one day I will “ride” again my friend’s dyno… it scares me a little, but I let you know then. Thank you.
Hello Pascal and Dave, thank you for your posts. I understand your point of view (1). However let me remark: this engine is a late SC 616/16 with an original pair of Solex 40 PII-4 as in the S-90 616/7. The main venturi was in both = 32 mm (not 28 as for the C 616/15 with Zenith, or even others…) (2).
Rebuild the old “Solexs” or buy new "Webers" was an option we take, change the venturi´s diameter wasn't an option. We have changed the distributor and set there a 123ignition – it works fine (hard to pick up from there an ignition pulse = rpm to the LM2)
(1) C J Murray says: - “(…) 28mm will be easier to jet but make less power and peak a few hundred rpm lower. 32mm will be slightly less responsive at lower rpm.”
(2) “Porsche Spec’s, Carburetor Specifications”.
Conclusion: I think they both fly 

[Joao Filipe]

Hello all. Well, never say never. So, as my old LM2 is working again (thank you Ingrid Bieser) finally I can do a graph again and continue testing my jets setting. I have changed my last "Magic Combination" twice and will show you the results. Air Correction Jets 225 instead of 220 = minus one (occasional) flat spot - this is the first graph made in the middle of the traffic, sorry; and the second one is in a short highway cruising near 3000 rpm with 140 Main Jet instead of 135 = nice response but one more (occasional) flat spot. You tell me. Thank you. Joao Filipe

[Joao Filipe]

Hello all. To celebrate 100 000 km soon (57 km are missing) I will post a photo of two spark plugs that are burning in brick color, aren't they? - No Photoshop! Cheers.