problem with the engine and weber

[frank356]

Hi, I have just bought a 356 b convertible 1960, with the 60 horsepower engine.

The car drives very good in the + 3000 rpm (garage did timing work and new sparks etc.). I still have a
problem with the 1000-3000 rpm's. The engine doesn't run smoothly and the engine's makes a 'firework' noice (bangs). The garage told me this was because of the webers. They have too large 'intakes' for the small engine. They suggested to go back to the zenith's, but i prefer the webers. They say that the pressure of the mixture going into the engine is too low, because of the large intake of the webers.

Does anybody know any solutions for my problem. Help would be very appreciated.

regards, frank.

[id10t]

I'd go subscribe to the 356talk list at www.356registry.org - no offense to pp, but there are a LOT of very knowledgable folks on that list that just don't feel like dealing with a bb like this.

[sixbanger]

Go back to the stock carbs.

[914Ghost]

which webers are you using?
I run dual 36mm dellortos with 28mm Venturis on my 1600 cc VW truck.
runs perfect and dell's flow better than webers- so my 36mm dell's flow like 40 mm webers. I run 40mm dell's on both my 914 and my 912- they run FLAWLESS. I haven't seen the engine in the 914 in 4 months!!
You can probably get smaller venturis (throats) for your webers and if you're running anything larger than 30mm then it could help.
Dont listen to anybody that says "GO BACK TO THE STOCK CARBS" without even tryting to figure out what your problem is. Sure put the Zeniths back on then try and find parts..good luck. ANYONE can tune a weber carb setup with a little patience and care.
1st Step. Make sure EVERYTHING ELSE is set correctly- valves, timing, points, etc....
2nd Step Any exhaust/ intake leaks? THat can give you some backfiring.
Now your problem- does it backfire through the intake *POP or exhaust *BANG! Those have different causes.
3rd Step : NOW GET A WEBER TECH BOOK. They're like $15. Seriously..why not? it will tell you what carbs you have whats wrong with them and how to fix it.
4th-You need to tune the carbs- Synchronize the MOVEMENT of the carb linkage- PRECISELY- this is an under valued procedure. Both carbs must work exactly the same.
They must open and close at EXACTLY the SAME TIME and the same amount.
There's your start, get that far and come back. Get the book and you wont need to come back and ask anymore questions....I know from experience.
-Bob O

[C. Clark]

Ghost,
What size Webers would you run on a 63 "Normal" 1600? aren't the stock carbs 32s? that said will Weber 40s operate correctly if jetted right? I run Weber 40's on my 69, 912 and after re-jetting I'm like you...I never look at engine... unless someone wants to see it.
Chas.
63/356
69/912

[914Ghost]

I personally like dellorto's, Webers work great- but my 914 runs like its fuel injected, absolutely smooth.
I would run 40mm webers on a 1600 with 30mm Venturis. I think the Vent's in the Zeniths are 28mm.
The reasoning behind venturi size (diameter) and airflow is this:
The airflow into the head draws fuel from the various ports in the carb- starting with the idle ports and then to the "power circuit'. These overlap usually- the car will run off Idle AND power circuits much of the time.
If you keep the vacuum constant (same throttle plate opening) the size of the throat (venturi) determines how "rich" the mixture is. A smaller venturi with engine speed say at 3k will effectively cause the mixture to be similar as a larger venturi at 3800rpm .. if vacuum is constant more air must pass through the carb per time as the venturi size decreases which is equivilent to increasing engien speed. ..? See...don't quote my numbers - its just for thought.
So you can get away with running 48's and 40mm venturis but you'll never produce enough 'vacuum' to run in the correct mixture range in the carb. You can laugh at the weirdo's who covet the 48 IDA webers and run them on their 1700cc engines- they're useless.
My stock 914 has 40mm Dell's and 34mm Venturis- those are a teeeny bit big, but it runs perfect, just lacks a little low end- better with 30's.
Any 1.6L VW / Porsche can run a 36-40-or 44mm Weber or Dellorto carb setup and be tuned just fine (better than stock). For a stock engine the 40's are great
just run a 28 to 32mm venturi depending on your cam.
Weber's are great carbs, but they're a little noisy (throaty) and require a tiny bit more upkeep than Dellortos- and I've found the 'feel' of the Dell's is smoother.
I'll shut up now...
Bob O

[C. Clark]

Ghost.
Thanks for the info, since you like Dells where do you get them? Most Porsche supplier I deal with seem to deal Weber kits, and what do they cost relative to Webers?are there adapters available or do the Dells bolt up?
Thanks again,
Chas.
63/356
69/912

[id10t]

As I understand it, the Dellortos are a "clone" of the Webers.

I have Weber 44 IDFs on my stock '65 C coupe, and they work fine. Most on the 356talk list would say that it is too much carb, unless some "inside" work has been done on hte engine.