Emulsion tubes ?

[walt347]

I need some advise with regard to some weber specific topics. Who can tell me the difference between F5 & F7 emulsion tubes for the 48IDAs ?

Is there a negative impact on performance, torque and streetability (I'm a 100% street driver) when installing the F5 tubes ?

Your help is appreciated.

Best regards,

[Cal Metal]

Walter:

The F7 tubes are pretty standard for the 48 IDA's. It is by design a tube that is a little richer and is generally regarded as the best all around tube for both street and track. I have never seen a factory set up without them and don't know of any racer with down draft Webers that uses anything else.

Side draft Webers DCOE's ofter use the F15 which is a little leaner. I have never analyzed the rationale behind that thinking but the F7 works well in smoothing the transition at around 2,200 rpms.

The F5 is similar to the F7 but is used primarily in the 40-46 IDA and the 40 IDA (3V) triple carb used on Datsun 240Z's and other 6 cyl. inline engines. Both the F5 and F7 have orifices in the lower part of the tube thereby enriching the charge for lower rpms and slight acceleration. Etubes are really important during the low end of the range and for acceleration. In flat out, pedal to the metal applications, they have really little significance on performance. At that point, it becomes venturi size, air corrector and main jet dimensions that are critical.

If you have a fax I can send you a pretty detailed pictorial of all Weber etubes. Call me at 1-800-356-0520 and ask for Dan.