Weber 40 IDF, on 1600 motor help please!!!

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56/69 beetle
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Weber 40 IDF, on 1600 motor help please!!!

Post by 56/69 beetle » Sat Aug 14, 2004 10:26 pm

I have a single weber 40 IDF on my stock 1600 single port the kit said it was jetted to work with this motor but when installed motor ran extremely rich and loaded up on idle (stop signs ect.)to the point of gassing out people behind me with fumes but the engine had great low end power and would rev till I thought it would fly apart. Now I downsized the idle jets from 55 to 50 thinking that would correct my problems and it did correct the loading up problem but I lost my low end power and some of my top end, my friend a long time VW mechanic says I should have asked him about webers, as he thinks they are junk and cannot be tuned to run on anything but race cars but I think there must be hope because lots of VW nuts run these carbs and are very happy.

So what jets do I need to run with my stock 1600? :?

another question, I am running this carb on an empi manifold with the single port end castings, would it be worth the trouble to switch to dual ports with this carb setup?

living_dead
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Post by living_dead » Sat Aug 14, 2004 11:07 pm

I'd goto dual port. Webers are great carbs.

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Post by turboblue » Sun Aug 15, 2004 9:27 am

My opinion? IDF on a stock single port is like a 650 Holley on a moped. That carb is rather large for your application. Think about it. You went from one 30mm throat to two 40mm throats. With that said, yes dual port is better if you are going to use that IDF. Try a 40-45 idle jet and about a 130-135 main. Not dissing your choice, but bigger is not always better. I bet it ran better with the Solex. If you are going to upgrade engine displacement, compression, cam and so on, your IDF can be made to work a lot better than it is for you now.
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JohnConnolly
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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by JohnConnolly » Sun Aug 15, 2004 3:23 pm

who did you buy this from, and why are they not helping you?

Those kits work fine if properly tuned and jetted. Most "experts" on webers have no clue what they are doing.

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bedlamite
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Post by bedlamite » Sun Aug 15, 2004 5:13 pm

would it be worth the trouble to switch to dual ports with this carb setup?
Yes, and put some 1.4 rockers and headers on at the same time.

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Perrin Aybara » Sun Mar 05, 2017 8:41 pm

So I'm looking at the same thing. But a little engine mods as well.

I have a 1970 Baja bug 1600sp with a w100 cam, 009 dist. and headers. (Basically equal length headers going to a collector then into a spark arrestor). I got a (I know people don't like them but it's what I could afford) EMPI 40 HPMX. I'm currently running what came with the carb so this is what I have.
.60 ideal jet
.135 main jet
.160 air correction
F-11 Emulsion tubes
.50 accelerator pump
28mm ventures

As of right now I'm have a hard time getting it started. Once started it seems to idle fine at about 1100rpm. Which is about what I had to run at when I ran the 30/31pict once I put the cam in. But just off idle it stumbles or has a flat spot. Don't really know the difference. Lol. But once off that spot it runs great. I expected a little more HP than what I feels like I'm getting but maybe I just need to change out jets to something different. Just seeing if y'all can help me out thanks.

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by sideshow » Sun Mar 05, 2017 9:00 pm

Perrin Aybara wrote:
Sun Mar 05, 2017 8:41 pm
... Don't really know the difference...
This is why a wide band is such a cheap and recommended tool.

But beware too-rich will sometimes show too-lean (on far ends of the scale) so it isn't idiot proof but compared to guessing and hundreds of A-B-A comparisons you at least know which direction you are tuning towards.

It doesn't really matter what the numbers are, you only care about what the engine likes.
Yeah some may call it overkill, but you can't have too much overkill.

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Piledriver » Sun Mar 05, 2017 9:08 pm

Welcome to the STF!

That sounds like the classic 009 flat spot, best taken care of by installing a later model std factory distributor with mech and vacuum advance and connecting the vac can to ported vacuum, which the empi carb should have.

Lack of properly working manifold heat on most weber single manifolds makes this worse, but the "009 flat spot" happens with stock carbs too--- the 009 is only a "high performance part" to people selling them.

You can help the symptoms a little by richening up the accel pump shot, and increase the idle jet greatly, but a working vacuum advance actually fixes the problem without destroying your fuel economy etc.

You can also limit the advance on the 009 to ~10 degrees by bending the stops in, and running far more initial timing.

Proper vacuum advance and mechanical is still better, but the recurve works on most vw distributors and usually helps, esp with a cam, even with vac advance.

A wideband is a very handy, even essential tool, but won't really help that much here.
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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by sideshow » Sun Mar 05, 2017 10:33 pm

Now actual calibration bits are going to cost you, I wouldn't touch anything EMPI for that sole reason, having a single helps cost wise. I would run a 009, it limits the options you have and in the beginning that is a plus.

If the reading I have done is correct, you might need; holes in the throttle plates, zero bypass, F-7

viewtopic.php?f=18&t=144344&p=1180918
Yeah some may call it overkill, but you can't have too much overkill.

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Perrin Aybara » Mon Mar 06, 2017 6:09 pm

sideshow wrote:
Sun Mar 05, 2017 10:33 pm
you might need; holes in the throttle plates

Thanks for getting back to me

Had to look up what you meant by wideband but got it now. That is something I will look into and wouldn't think it would be that hard to install. EMPI already predrilled the holes in the throttle plates so I'm good there. One thing after doing some research today is a problem with my heat risers or lack thereof. I have the tubes but my exhaust doesn't have the riser hook-up. So I didn't install the tubes. Now I'm looking into finding weld on risers so I can install them. I didn't think they were that big of a deal where I live in SoCal as my 30/31 ran great without them. But now I have a lot more air and fuel going in and could be condensing down the tubes. I looked into the f7 f11 thing and I got mixed reviews. Some people said to run the f7s and other told those people the f11s were fine. So I don't know.

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Piledriver » Mon Mar 06, 2017 8:04 pm

Get the heat risers hooked up before doing anything else.

I suggest you run one via small steel tubing to the collector, rather than just to the other side.
Much more likely to actually work well.
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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Marc » Mon Mar 06, 2017 11:23 pm

Piledriver wrote:
Mon Mar 06, 2017 8:04 pm
Get the heat risers hooked up before doing anything else....
Finally, something we see eye to eye on. I guess we'll need to agree to disagree on some other things you mentioned earlier. The "deluxe" manifold that exposes more of the intake runners to preheat is mandatory IMO for street use, but since most all aftermarket exhaust systems don't provide squat for heatriser flow the modification you mentioned, extending one pipe to a low-pressure point, should also be high on the list, before jacking around trying to compensate with overly-rich jetting and big pump shots.

009's are NOT the problem, they just get the rap when other problems exist which they are incapable of masking like a vacuum-advance distributor can. Admittedly the quality control on them isn't what it used to be (especially the Chinese clones I've seen) but a "good" one can work just fine.

Very few non-stock carburetors provide the correct ported vacuum signal; even mismatched stock components can leave you no better off than with a centrifugal-advance distributor. The 49-state 4-speed 1974 Type I distributor known as "the" SVDA doesn't get all of its centrifugal advance until ~3800 RPM - higher than many cars ever cruise on the highway - so if the vacuum signal is insufficient they can give less total timing under real-world conditions than the maligned 009.

Jacking up the initial timing to cure a flat spot is hard as hell on the piston ring lands - you may not be able to hear the detonation going on, but it's happening.

A leaner mixture is harder to light and can take more time to burn completely, so more spark advance on "step-off" will help with a hesitation caused by a too-large intake tract that's insufficiently warmed. By the same token, most carburetor setups don't create any conditions that require anything more than a stock-style ignition, but the single center-mounted 2-bbl often will noticeably benefit from a higher-energy spark. Read the testimonials of folks who swear by their new $200+ ignition systems and you'll find an underlying theme, perhaps half of the satisfied customers are running a single IDF. Personally I prefer to address the cause of the problem rather than throw money at it until the symptoms go away ;)

What works in a temperate climate can be hopeless in cool/damp weather. In the Pacific Northwest, a single IDF is horrid to live with on the street about 9 months out of the year and would be about the last setup I would recommend - that said, I'm planning on using one on my trike with the larger engine it's getting this year, it shouldn't be much worse than the 34DMTR I'm running now - it runs great with NO preheat in the summertime, but it won't move out of its own way until it's warmed up for 5-10 minutes this time of year :)

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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by Piledriver » Tue Mar 07, 2017 2:55 am

We agree on more than we disagree, and most of that depends on application.

With a cam, the additional initial can help greatly due to low DCR and large amounts of inherent EGR (reversion) due to the bigger cam at lower RPM, have not tried it on a stock T1, but it does wonders for a T4, even stock, for several hundred thousand miles.
A stock 1700cc T4 is a totally different critter than a 1600DP, though, despite the layout similarity.
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Re: Weber 40 IDF, on 1600 motor help please!!!

Post by ainokea » Sun Mar 12, 2017 7:35 pm

Check the float adjustment, 30.5mm, 10.5mm,

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