Ok, Webbers - but which ones??

[dave harris]

I've search on this and the only inputs I've found said that the IDF's were a better choice for the street. When I contacted Pierce about the choice I told them I was planning to put them on a 331 stroker assembled to produce ~ 425 HP. They gave me the following answer;

"The 48 IDA's with 40mm venturis and 3rd progression hole added is the smoothest running combo in that range."

Not what I expected - also, I've not heard of a "3rd progression hole" and can't find it described in any of my webber books - -

Need opinions from those more experienced!

thanks

 

[David Briggs]

IDF's are working fine on my 347, which I specced out for that same power level. Excellent driveability and idle, great response and torgue. As advertized.

 

[Ron Earp]

Pierce seems to be hit or miss on the helpfulness side of things. I have gotten things from them in the past but a couple of calls to Inglase has convienced me that they are more knowledgable, more helpful, and not "hit or miss".

 

[Trevor Booth]

The third progression hole refers to an additional hole drilled in the throttle body at or near the butterfly. The purpose is to smooth out the transition when you crack open the butterfly. Webers supplied as OEM to some manufacturers had 1,2 or 3 holes dependant on the particular vehicle for which they were setup. It has been my experience that 'off the shelf' units had 2 progression holes. For road use some benefits can be gained (smoothness) in experimenting with progression holes (number and size). For competiton use I do not bother to fiddle with them.
The position of the hole(s) relative to the butterfly is critical. If you have the Weber tech manuals it is explained in detail. To set webers up correctly you need to understand the reasonings behind the function of the individual components. Make provision in your exhaust system to fit an O2 sensor, the portable hand held meters available to day make it an easier job either on road, or on dyno, experimentation. If you spend the time the benefits are substantial.
Ciao

 

[dave harris]

Thanks Trevor,

That's what I thought was being talked about (I took a magnifying glass to the photos and they show 3 progression holes - two up by the butterfly and one down lower).

cheers