Weber's Affair

[Joao Filipe]

Hello all, I have just "close" my last topic "Solex´s Affair" - viewtopic.php?f=1&t=41281) and reopen a new one "Weber's Affair" for an obvious reason: I decide to change my old Solexs for a new pair of Webers. May be one day I will (learn how to) repair the Solexs but not for now, sadly.
So, let me show you my firsts AFRs with the LM-2 with those pair of Weber 40 IDF 70 that I bought (especially) from Germany. The jet setting they send me should be suitable for a 1600 SC, stock engine… are they?

[Bruce Smith]

Joao - What mains/idles are they sending you?

- Bruce

[Joao Filipe]

Hello Bruce, I will show it next, thank you.
The second round, with other jet setting did it a little better? You tell me. I found many reputable opinions in the Registry forum but there aren´t two equal engines (...) and no time yet to try them all.
The tests were done with the engine out of the car and without charge (no, I don´t forget what C J Murray have said before: “To evaluate jetting you need to be under a load”… Well, as soon as I can (with the engine in the car, I will visit my friend - with a dyno 100 km away - and will do it then under load, I hope).
However I’m still worried about having too rich mixture between the 40’ and 50’ (AFR ≈ 8.5 – 9), reeving among 2200 and 3400 rpm´s. Please tell me what I should do to stay, ideally, in the yellow zone (AFR ≈ 11.5 to 12.3). Wath to change? Thank you.

[Joao Filipe]

Let me show you the adapter for the collectors (…) and also a “bug” in the rpm recording (visible in the first graph) that I can correct with Ingrid´s help (from Innovate Motorsports .de). I will show you the plan “how to link the cables and stabilize the recording of rpm ” without getting frustrated. Much obligied!

[C J Murray]

The LM-2 has a recording feature. You don't really need a dyno if you just drive around with the LM-2 and record data in specific rpm ranges at a steady throttle position AND rpm ranges while accelerating, partial throttle and full throttle. You don't want to attack everything at once. Start with the idle jet and get happy with the way the car runs at small throttle openings below 2700rpm. The correct idle jet should idle well with the throttle stop idle speed screw barely turned in and with the idle mixture screw between 1/2 and 1-1/4 turns out. Once happy, DO NOT CHANGE THE IDLE JET TO CORRECT A TRANSITION STUMBLE. Problems with stumbles are caused by bad main circuit tuning.

[John Clarke]

Not again!
Just get some Dellortos !
Jay

[C J Murray]

How many world championships has Dellorto won? This ain't no Ducati! Ok, enough fighting.

[Joao Filipe]

Hello C J Murray, thanks for the advice. I will be glad to put all that stuff in the car: 2 batteries, 5 devices (LM2, SCO2, Timing Light and two O2 sensors) plus several cables (some crossing the entire car and windows) plus the extinguisher and wife recording multiple and different trips. Well, I will tell you later. Wish me luck!

John Clarke, which was the engine? And what was the original carburettor? From the beginning I count 9 different types of carburettors for the 356 (even Webers, Solexs, Zeniths, but no Dellortos). Thank you.

[C J Murray]

my guess for a 1720cc street engine

IDF40
32mm venturi
F11
50 idle-maybe 47
125 main-130 max
190 air-may need 200 air to clean up transition and that may require 130 main

[Brian R Adams]

my guess for a 1720cc street engine

IDF40
32mm venturi
F11
50 idle-maybe 47
125 main-130 max
190 air-may need 200 air to clean up transition and that may require 130 main

There was a time when the first 40 IDF item changed for a 356 was emulsion from F11 to F7. Has the thinking on emulsion changed?

Brian

[Joao Filipe]

Murry, what a guess! Thank you! Well, I already ordered a 125 main (even a 120), a F7 e-tube and others jets and tubes. However this is a 1582cc (95 hp) not a 1720 cc and this can justify the difference.
Someone in the forum said (some time ago, in 2003?) – “after spending a lot of dyno time” the best with the Webers was:

• 28mm venturis
• 115-120 mains
• 175 ac,
• F7 e-tubes
• 50 idle

I believe this was certainly a car with a main venturi smaller then 32 mm. All of them, except the 1600SC, has smaller venturis. From the very beginning we saw: 23, 24, 26, 28, and 29. The SC – 1960 has 32 mm. Street engine, correct?

[C J Murray]

Porsche used 32mm venturis on 1600cc engines. Depending on cam they should work fine but peak power will come a few hundred rpm higher than the 28mm. F7 just cover up poor main jetting...waste of money and makes car too rich. 175 airs too small so mains will come in late and tuner mistakingly fixes this error with the F7. Try F11-50-200-130-32mm.

Brian, F7 is very rich and intended for American V8s but it will fix a late/lean early main. It will never be as good as a F11 and correct main and air jets though. The air jets usually need to be around 200 to allow enough atmospheric pressure in to get the mains to kick in quickly enough to take over from the idle jet/transition ports. Too small air jets are slow to get going. It's a timing thing more so than a mixture thing. After you get the main to kick in on time via the air jet you then adjust the main jet to get the mixture right. There is one setting that is best but there are a number of settings that may get acceptable results but the hesitation in a Weber can always be removed by having the right air jet.

[Brian R Adams]

Brian, F7 is very rich and intended for American V8s but it will fix a late/lean early main. It will never be as good as a F11 and correct main and air jets though. The air jets usually need to be around 200 to allow enough atmospheric pressure in to get the mains to kick in quickly enough to take over from the idle jet/transition ports. Too small air jets are slow to get going. It's a timing thing more so than a mixture thing. After you get the main to kick in on time via the air jet you then adjust the main jet to get the mixture right. There is one setting that is best but there are a number of settings that may get acceptable results but the hesitation in a Weber can always be removed by having the right air jet.

Thanks. Good to know - if I ever run Webers again in the future.

Joao, who made that adapter plate for the Webers?

Brian

[Dave Wildrick]

Someone in the forum said (some time ago, in 2003?) – “after spending a lot of dyno time” the best with the Webers was:

• 28mm venturis
• 115-120 mains
• 175 ac,
• F7 e-tubes
• 50 idle

I believe this was certainly a car with a main venturi smaller then 32 mm....

Joao,
It was John Willhoit who said this:

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

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]

[Joao Filipe]

Joao, who made that adapter plate for the Webers?

Brian, I will send you a private email with data from whom, in Germany, I bought the webers, adapter plates and filters. Thanks