Can we talk Webers here, even if not on Alfa?

[oz3litre]

It is 7 or 8 years at least since I drove the car but the rev thing and the heat related issues were two different things. We didn't realize that the fact that it revved very quickly to 6,000 and then choked was due to valve bounce because we thought the springs were fine. We were looking for fuel related causes like pressure and flow etc. From memory the heat in the carbs caused flat spots, trouble idling and difficulty in starting. It was more of a problem in traffic than on the open road or drag racing. The carby heat wasn't due to the engine running hot because according to my cylinder head temperature gauge it was OK and it never felt any hotter than a normal engine. I am sure it was due to heat soak through the short cast alloy manifolds. As I said, I didn't come up with a solution at the time. My youngest brother has the car now and is rebuilding it gradually and will have it going better than ever I should think. It was never really daily driver material but good fun. It is a 1956 Beetle and my mother christened it "Big Bertha".

[AlfaDuc]

Quote:

Originally Posted by JRatto It pulls off idle ok, not as crisp as when cold, but if I open throttles (and this is after "hot start") and try to accelerate, it will nose dive around 2700rpm, only if throttles are open at pretty wide angle.

[oz3litre]

My 1984 GTV 2 litre stumbles at around 2300 RPM and it has Dellortos. I improved it a lot when I disconnected the fuel breather system in the boot and loosened the cap a bit and readjusted the mixtures, but I haven't managed to eliminate it altogether yet. The trouble is that it corresponds to city speeds. I plan to check the ignition leads etc at some stage. I haven't stripped the carbies yet because I am not sure it will help at this stage and the kits are $50 each. Any ideas on this would be helpful for me too.

[Slash]

Quote:

Originally Posted by JRatto Yes this engine is in a '67 Beetle. It has all of the factory cooling sheetmetal in place including a stock VW late fan housing, factory cooler, and a dual-fan Setrab cooler mounted next to transaxle. The fan intake is open, as a stock VW is. The bottom of the decklid is propped open about 4" to allow more air. The fuel line is routed through floorpan tunnel, away from heat. The regulator is mounted in front of fan housing, on firewall. Pump is up under fuel tank, in nose of car (cool).

[JRatto]

Quote:

Originally Posted by oz3litre The original fuel tap/outlet on your tank might be on the small side. If I remember correctly we put one from a type 3 on mine because it had a larger diameter outlet pipe. Have you taken the outlet unit off and checked that it is clean and unobstructed? As I said my car ran easily to 8,000 RPM once we fitted dual valve springs. I too had an electric pump up front and the needle and seats etc were stock 44IDF. Before that it was only pulling 6,000 due to valve bounce. The springs that were in it at that time were single, supposedly high performance ones. The dual springs made an incredible difference.

[Alfar7]

I had a long post written & lost it in a power failure!

Short synopsis: Way to large carb internals for air flow.
Suggest:
34mm choke tubes will flow over 200CFM in this carb
3.5 Aux. Venturi to match fuel use
F9 or F11 emulsion tubes. (F2 are for high fuel volumn & large jets)
Then use 160 mains & 160 air correctors (pulling fuel higher in etube )
If lean at top end go to 150 AC.
just use a larger needle & seat. 3.0 should be plenty.
If lean at idle change AC carrier to smaller. Idle jet itself is likely too large.
You are not likely running out of fuel. Just not creating airflow to generate fuel delivery. If you feel the need for more volumn, look at the inside & you will see a blocked off chamber. Drill or slice a opening from the fuel chamber into it at the bottom, so that fuel can occupy this space, thus increasing volumn & supply..
I still have a bit of IDA pieces & might have the Needle jet, etubes etc. Have a large supply of Weber tuning parts. Used 52 IDA on GT2 Mazda.
Good luck
Rj

[JRatto]

Quote:

Originally Posted by Alfar7 I had a long post written & lost it in a power failure! Short synopsis: Way to large carb internals for air flow. Suggest: 34mm choke tubes will flow over 200CFM in this carb 3.5 Aux. Venturi to match fuel use F9 or F11 emulsion tubes. (F2 are for high fuel volumn & large jets) Then use 160 mains & 160 air correctors (pulling fuel higher in etube ) If lean at top end go to 150 AC. just use a larger needle & seat. 3.0 should be plenty. If lean at idle change AC carrier to smaller. Idle jet itself is likely too large. You are not likely running out of fuel. Just not creating airflow to generate fuel delivery. If you feel the need for more volumn, look at the inside & you will see a blocked off chamber. Drill or slice a opening from the fuel chamber into it at the bottom, so that fuel can occupy this space, thus increasing volumn & supply.. I still have a bit of IDA pieces & might have the Needle jet, etubes etc. Have a large supply of Weber tuning parts. Used 52 IDA on GT2 Mazda. Good luck Rj

[101 Alfa Mike]

You might want to measure the intake vacuum at max load/rpm.

I'm currently working on my 750 1300 Giulietta. The old Alfa Owner's are full of advice to go to bigger chokes, but a temporarily installed MAP sensor shows there is no significant pressure loss at max load/rpm. Guess thats why the factory went to slightly smaller chokes on the 1600 Normals.

Mike R

[tubut]

Quote:

Originally Posted by AlfaDuc Well, I have the same performance with a '65 Spider Veloce (totally stock setup for Webers, cams and mechanical fuel pump with stock filter/ pressure regulator). The flat spot around 2700 rpm has been there for the 10+ years I've had the car. Carbs / jets have been cleaned at least once, synch is dead on, float levels per std. At times I think there could be an electrical issue (changed the coil lead once which helped a lot, for a while). Cleaning the contacts on the coil and making sure the junction between the leads and connectors to the coil are tight (no frayed wires, etc.) will also help. But I still have the 2700 rpm stumble. Jim

[Alfar7]

[QUOTEThanks. Typically, hot street Volkswagen motors above 2000cc run 37mm+ venturi. In fact a friend of mine was utilizing 34mm vents in his 2275cc engine, will not run past 159 hp @ 5300rpm on dyno. 40mm vents on dyno allowed 7100/ 213hp & 176ft-lb @ 5500.
][/quote]

Yes, but do you want HP or drivability?

[JRatto]

Quote:

Originally Posted by Alfar7 [QUOTEThanks. Typically, hot street Volkswagen motors above 2000cc run 37mm+ venturi. In fact a friend of mine was utilizing 34mm vents in his 2275cc engine, will not run past 159 hp @ 5300rpm on dyno. 40mm vents on dyno allowed 7100/ 213hp & 176ft-lb @ 5500. ]

[101 Alfa Mike]

Quote:

Originally Posted by AlfaDuc Well, I have the same performance with a '65 Spider Veloce (totally stock setup for Webers, cams and mechanical fuel pump with stock filter/ pressure regulator). The flat spot around 2700 rpm has been there for the 10+ years I've had the car.

[papajam]

Have you always run the D7EA plugs? I ask only because the 7 is the hottest plug in the DxEA series and considering your engine mods is perhaps too hot.

[AlfaDuc]

Quote:

Originally Posted by 101 Alfa Mike What you have is the dreaded flat spot between the progression circuit and the main circuit. My '65 Spider Veloce was the same way for years! Thought it was just the nature of the Veloce cams until I started messing with the carbs. The following will help - 1) Idle jets with a smaller air hole, typically F8 or F9's i/o the F11's 2) Higher fuel level 3) Smaller air corrector jets. 4) Different emulsion tubes. This is rarely recommended, but some spare F34's with the 2 top holes plugged worked for me. Mike R