Printable Version of Topic

Posted by: RobW Mar 7 2017, 03:29 PM

How can you tell what size Webers you have? Is there a website for /6 motors that lists out the configurations? I want to see if the 2.4 set up I have (just rebuilt) will work on a 930 / 03.

Also, how do you measure the headers, will they work?

Posted by: mskala Mar 7 2017, 03:37 PM

Not sure what exactly you're asking. Webers are very configurable.

The main body comes in:
40mm IDTP (T motors originally)
40mm IDA
40mm IDS (S motors originally)
46mm

Also PMO makes a compatible one in:
40mm
46mm
50mm

Also you can send 40mm Webers to Performance Oriented and he will make them 42mm.

What size you need depends on how much air you'll need.
I _think_ from the Bird Board that people start needing 46mm for their 3.2's or hot 3.0's.

Mark S.

Posted by: mepstein Mar 7 2017, 03:42 PM

46mm webers go for big bucks. I sold a set for $4800 that were in decent shape but nothing special. Probably could have gotten more if I was patient but sold them to a good customer.

Posted by: RobW Mar 7 2017, 03:51 PM

Thanks. Is the size and type stamped somewhere?

The 3.0 is a ROW 78-79, which is the same as US at 180 HP with the CIS. It has the original CIS on it, but I figure I can use the carbs.

Posted by: jmill Mar 7 2017, 04:07 PM

Do you have Bruce Anderson's book. He makes some recommendations in there for Weber sizing for just what you want to do. This is for the 3.0 SC:



Attached thumbnail(s)

Posted by: flyer86d Mar 7 2017, 05:33 PM

The 40 or 46 is the throttle bore size in millimeters. Flip the carb over and measure. I think that the carb type is stamped into the carb body. I'll look at the set that I have in the morning. 40 IDS are easy to identify as they have a brass squirt tube that goes up and curves pointing straight down the center of each venturi. Bruce Andersons book gives you a good starting point as well as some of some of the formulas to calculate venturi size and baseline jetting. Most parts are available thru PMO as well as others.

Weber's like clean fuel. Idle jets clog easily. Weber carbureted cars run from one third to one half way thru their range on the idle jets. It is dismaying to have a cylinder lay down when you are planning to blow off the guy next to you at a stop light or toll booth because of a clogged idle jet. Also, the idle circuit likes to be a little rich so they transition to the mains without a stumble, particularly the 46IDA's. Our old track car had them and those who tried to keep up said it was like following a refinery.

Charlie

Posted by: Mark Henry Mar 7 2017, 06:27 PM

Size and version should be on the valve cover side/outside when on looking at them installed on the engine, it's on the float bowls.
One bowl will have a big EW and the other is stamped with the info. The stamping is quite small.

They will work on a 3.0 just fine. You'll likely have to re-jet them and depends but you might need bigger venturis. If they are weber venturis the size is cast into them and you might be able to see this looking down the throat.

I'd invest in a WB 02 meter, it will save you a lot of jetting guesswork.
Also be aware a lot of tuners (like me) use jet reams to size jets, so while the size number may be correct, they also could be way off. You can buy jet size gauges.

I'd go over to the Performance Oriented site and read all the tech pages.

For parts the best price and selection I found is http://youroil.net/weber_carb_parts.html
They are the east coast PMO source and it's a much easier to navigate than the PMO site.

BTW besides the versions listed by mskala they could also be made in Italy (best and OE), Spain or USA.

Posted by: Mark Henry Mar 7 2017, 06:44 PM

This pic of one of my carbs the version info is on the left in the little box/boss beneath the word Weber

Posted by: Bgyglfr Mar 7 2017, 07:11 PM

As mark said above. 40s will work on a 3.0 unless it is upgraded significantly. Ida, ids, Idt will all work. The idtp are odd but can also be made to work well with some mods. Most likely your carbs only need a venturis, emulsion tubes, and a rejet since you already had them running on your 2.4. I have a bunch of jets and venturies for webers around so I might have what you need.

Posted by: Justinp71 Mar 7 2017, 07:16 PM

I had 40's on a mid horse 3.0 and they were perfect. I think they are the right size for a 160-240hp motor.

Posted by: larryM Mar 11 2017, 02:07 PM

start by looking at the venturis - IIRC they have a mm size mark on 'em -
on any heads from an injected car you will need the spacers that cover the injector cutout - PMO, Pierce & others sell 'em

http://forums.pelicanparts.com/porsche-911-technical-forum/650058-weber-venturi-size-question.html

http://forums.pelicanparts.com/porsche-911-technical-forum/299927-weber-venturi-size-what-difference-does-make.html

http://www.performanceoriented.com/throttle-body-and-main-venturi-sizing/

Mike Pierce's pages - https://www.webercarbsdirect.com/Technical-Information-on-Weber-Carbs-s/74.htm

Posted by: r_towle Mar 11 2017, 04:23 PM

QUOTE(RobW @ Mar 7 2017, 04:29 PM)