Im sitting here trying to rebuild my 40 IDFs I got last week, but I realize they are different carbs. I find the stamping, and one says "40 IDF 13" and the other "40 IDF 15". I guess there are different series? I saw in the Haynes manual there was a 28 adn 29 series that was closer to the 44 IDFs then the 40s, but I see no mention of the 13 and 15 series. Are they compatable with my 2.0? What modifications, if any, are necessary to make? Do I need new carbs??? Thanks!

I'm not an expert but that may just mean right and left. They changed the numbers later on, and some say 40IDF xxL or 40IDF xxR or something. I had a set and the numbers didnt match either.
Use the right jetting and vent's and you should be okay.
I would say as long as its a 40 IDF who cares?
Rebuild em' and drive.
You can tell if you have the early ones or late ones by the style of accelerator pump. One has an
eccentric "flipper" and lever (early) to activate the pump, and I think one has a more common style rod&linkage. I don't know if one is better.
Bob O

And You'll get different opinions, but if you have a correct 2.0 w/ the right heads and valves, 40 IDF's are a teeensy bit small. You can make them work, but you may have to go as big as you can on vents, and I don't know if even then you'll get max out of the engine. Make sure you get a good professional opinion on jetting for your combo, 40IDF's work great on a 1600/1700 VW bug, so I don't know about a 2 liter.

Matt, Ghost is probably right about the numbers indicating left and right carbs. I questioned similar numbering on my carbs and found that was the case. I won't worry about it.

As far as size goes, 40 IDF's will work well on a 2.0. I used a pair of 40's with 28mm venturis for quite a while on my mildly tuned 2.0 (mild cam, ported heads, balanced) and was happy with their drivability and fuel mileage. Very tractable. They might run out of steam at high RPM's but I never really pushed it beyond 5K so I didn't miss anything. If you have 28mm vents and want more you can increase the breathing capability by going to 32mm, but of course you'll have to rejet.

Mike

There's nothing wrong with 40IDF's on a mild 2 liter engine. Just compare the cross section of 4 40mm carbs to that of one stock FI throttle body. The standard 28mm venturis should probably be changed to 32mm (even bigger are available), and the jets will need to be changed too. You get better mid-range response with 40's over 44's. And there's room for a lot more perfomance with a little work, unless your engine is built to rev over 7000rpm. Many people select a carb that's too big for their engine IMO. A chassis dyno tuning session can make a big difference.

Chris is right most people over carb there motor
with out doing the internals on there motor."flowing" youre motor is a complete process
i use 36 IDFs on a 1.8/and a 1.7 i get screaming performance and great gas milage
40 IDFs on a stock 2.0 should work great
oh and the # diffrence is a left and right thing as long as the venturies match and all the jets, youre in great shape

when you have it apart write down the jet, air correction sizes so you know what you have if you have to make changes later on.

kevin

What Kevin said.

Hi,

The 40 idf 19 came with 28mm venturi. The 13 came with 32mm venturi. If someone has a Weber book they can tell you for sure. I don't recall anything about the 15, and my weber tech book went to the guy I sold the carbs to. I do know that weber used to make right and left handed carbs, but has stopped this practice.

Carlos

Old man still has a good memory. check this link
Weber tech info

A Quick google of 40idf13 turns up.

http://www.mirafiori.com/faq/tcmods.pdf

Which says in part about page 18,



FWIW and HTH................................

Specs here.

http://www.mirafiori.com/faq/content/idf.html

chris,

Is EP limited to 40IDF ?

If so, how do you set them up? I think they allow for a 38mm vent but I don't see one that size available as a standard part.

dr

I only spoke from experience with carbs.
And most of you have more than I do.
I just know I switched from 36 Dellorto's to 40's and went up a couple sizes in vents and noticed a HUGE, well okay noticable, difference in smoothness and power thru the whole RPM range. And I only have a 1.8.
No change in mileage and the plugs read nice.
I've used 40IDF's with 28 or 30mm vents on stock VW bug engines (w/engle cam) and conservative jetting and they work beautiful. No loading up, no plug fouling all year round. Just seems like with the larger carb size you have the option to increase power by reconfiguring, but you're limited with the smaller 40's.
BUT, I'd go with what the smart people say, because they're smart.
Bob O

Yes, EP has a 40mm carb limit. No venturi restriction, although I can't see the point of running no vent. except at places like TWS or or Daytona.
FP has a 38mm venturi restriction, but I am running 36's. I can have 38's made easily at the same place. The top of a 40IDF needs to be opened up above the main choke to increase the maximum intake air available for high rpm.
One thing to do is modify the secondary venturi. This is a picture of what I do.

Wow, you guys are great! Thats so much information. The left and right thing looks right, because one side appears to have 2 fittings for the fuel line (1 in and 1 out i assume) and the other has only 1 (for the in side).

I'll shop around for a 32mm venturi. I am going to rejet it, no question. I was thinking of spending a few hours on a dynometer locally to maximize performance. I ran into a few problems today (mainly finding enough space in the driveway to work on the 914), but it looks like tomorrow im going to drop my engine! I think everything is set to go, as per the Haynes manual.

If the link to the specs I posted is correct they already have 32mm venturi.....

Good luck with them.