TheSamba.com :: View topic

Wed Jan 15, 2014 12:07 pm

Here are some photos of one of my Weber 40 idf throttle plates.
The question I have is will this cause trouble with the air fuel mixture adjustment being that part of the lowest progression port is exposed?
Idle speed screw adjusted 1/2 turn after contact

Idle speed screw 1 full turn after contact. Have been having issues with idle mixture screw not responding with adjustments.
Other carb has the lower ports blocked at 1/2 turn out.
Any help will be appreciated.
Thanks, sorry for any posting issues using phone for post.

Wed Jan 15, 2014 5:09 pm

Need progression hole covered to adjust a/f mixture.

Wed Jan 15, 2014 5:09 pm

Need progression hole covered to adjust a/f mixture.

Wed Jan 15, 2014 5:10 pm

Need progression hole covered to adjust a/f mixture.

Wed Jan 15, 2014 5:31 pm

1/2 turn after contact?? wrong, DOn't do it like that.

Bench set the carbs equal either by eyeballing the first hole half exposed, or set with feeler gauges, then later on the car try to adjust same amounts to keep them equal.

Wed Jan 15, 2014 6:24 pm

Modok

Meant 1/2 turn after idle speed screw touches throttle shaft arm.
Was going by lean best idle procedure. In order for lower holes to be covered on this carb idle speed screw can only be opened about 1/4 turn or less then I have a reading on snail gauge of about 3
I will try the way you suggested by lining lower holes 1/2 open on bench. I didn't know if I could a proper idle mixture adjustment with any of the lower holes open? I had thought they needed to be covered for proper idle mixture adj.

Thanks.

Wed Jan 15, 2014 6:34 pm

saw2 wrote:
Meant 1/2 turn after idle speed screw touches throttle shaft arm.

Thanks.

I get it. There is even some instructions that come with the carb kits to set it like that, but it's very bad advice, because as you can see one carb is able to close more than the other!

Now, what does this mean??? it could mean the throttles are not aligned as well as they could be, but that's not necessarily a big deal.

The first hole half open is the correct idle speed angle IMO.
There is such thing as carbs machined with the holes in the wrong place, but Get out the feeler gauges and investigate and I think you'll find out it's ok

Wed Jan 15, 2014 8:06 pm

modok wrote: saw2 wrote:
Meant 1/2 turn after idle speed screw touches throttle shaft arm.

Thanks.

I get it. There is even some instructions that come with the carb kits to set it like that, but it's very bad advice, because as you can see one carb is able to close more than the other!

Now, what does this mean??? it could mean the throttles are not aligned as well as they could be, but that's not necessarily a big deal.

The first hole half open is the correct idle speed angle IMO.
There is such thing as carbs machined with the holes in the wrong place, but Get out the feeler gauges and investigate and I think you'll find out it's ok

Will I get proper idle mixture adjustment with lower holes half open?

Wed Jan 15, 2014 8:59 pm

I donno?? why don't you try it first, like I said. Then get them set and synchronized. IF you have problems then take them off again and observe where they are set.

If it is too rich and flooded out so you can't set the idle then measure the size of the idle jets and look for possible ways fuel is leaking past them, look at the cold start system, it can do that too, check fuel pressure and float height and float weight.

Try again, still problems?? take them off again.

if the holes are FULLy covered then you will want to close the bypass screws or modify the throttle plate to bring them open sooner.

If the hole is more than 1/2 open consider opening the bypass screws or drilling small holes in the throttles to get them where they are supposed to be.

this is not any special weber thing, it will say the same is a holley manual!

What's nice about these is you don't have to reach for the drill or file right away, since they ahve an adjustment for that. The bypass adjustments!, which WERE factory preset in italy, so I usually leave them alone and it's FINE.
Have your carbs ever been to italy?? Hmmm, if not then maybe they were not pre-set. who knows. I do see them in the picture, that's what they are for.

Thu Jan 16, 2014 9:09 am

Nope, never been to Italy that I know of, Spanish Webers. No cold start system.Here are my carb settings.
50 idles
115 main
180 air
f11 e tubes
2 3/4 lb fuel pressure
10mm-32 mm float level.
Starting jetting recommended by ac.net.

Engine info.
1600
8.2: 1 comp
Engle w100 cam
ac.net L3 heads
ac.net SVDA
Tri- Mil 1/1/2 header
Dual Weber 40 IDFs

I will try your suggestions as carbs are very easy to get off, engine is on test stand then on glass street buggy.
What little I have ran them they are very rich on idle A couple of cylinders had little response with idle mix screw adj. Will look for idle circuit issues. This is the first time with these carbs.
I know it is a carb issue as with weber ICTs I just took off engine ran great.
Not really sure why I messed with it but most said I will notice a lot of difference between the dual 40 IDFs vs. 34ICTs. Also installed lightened flywheel at same time as IDFs
Always lookin for a little more I guess?
Thanks.

Thu Jan 16, 2014 11:28 am

Have the butterflies been taken out to replace the bearings? maybe one is out of place and not letting them both close. I would try to loosen the screws on both butterflies and see if it will close all the way, make sure to back the throttle stop is backed off.

Casey

Thu Jan 16, 2014 12:07 pm

Tried that, loosening butterfly screws then letting them settle in and tighten. This is how they ended up.

Thu Jan 16, 2014 3:34 pm

Try swapping them with the other carb and see if the issue still exists. They should not be exposed when not contacting the throttle lever. They may be bent.

Thu Jan 16, 2014 5:38 pm

should say 78 on the plates. are the throttle plates in the wrong way??

Thu Jan 16, 2014 9:44 pm

Yep, 78 on the plates. They are installed correctly. Switched plates between carbs, found a little nick on edge of one plate. Lightly sanded it off and it did make a little difference. All lower holes are now covered when idle speed screw in not touching throttle arms. One of the lower holes in one of the throats is a few thousandths lower, but I dont think it is really enough to make a difference.
Will give them a try and try to figure out idle mixture adjustment issues this weekend. Will report back.

Thanks for info and ideas.

Sun Oct 29, 2017 2:16 pm

Sorry to but in, but it was suggested I gap the throttle plates to .003 and back the idle speed screw out one turn. Is the lowest progression port supposed to be exposed? At .003 the lowest/first progression hole is half exposed. Backing the idle speed screw out one turn resulted in none of the progression hole being exposed. Is there a general rule of thumb when it comes to the progression holes? Thanks!

I've 40IDFs on a type 4 2.0

.003
[img]https://www.thesamba.com/vw/gallery/pix/1706728.jpg[img]

.003 baced out one turn
https://www.thesamba.com/vw/gallery/pix/1706727.jpg[/img]

Sun Oct 29, 2017 3:36 pm

I do not use the gap method.... I setup by "lean best idle procedure".....

You can gap throttle plates all you want, but as soon as you touch the idle speed screws all the effort to gap butterfly goes out the window....

http://www.piercemanifolds.com/category_s/313.htm
http://www.piercemanifolds.com/category_s/311.htm
http://www.piercemanifolds.com/category_s/312.htm

There is good read here...

https://www.thesamba.com/vw/forum/viewtopic.php?t=572107

And I really think this method is superior for sync...

https://www.youtube.com/watch?v=Y_WDF6glD5k&t=166s

Dale

Sun Oct 29, 2017 4:09 pm

All of the methods have pros and cons.

If you bench set the carbs so the first hole is half open, that does not necessarily mean that's going to be the right adjustment, however when installed you will know both sides are adjusted equal in relation to the transfer ports, and be able to tell what needs to be done to make them right if they aren't.
For instance, if one side needs more air than the other, you will know the right thing to do will be open the air bypass ports on that side, or close the bypass ports on the other side. This is what the air bypass ports are intended to adjust. Originally they were pre-set at the factory to be equal but, probably not anymore.

Also, see this thread, everything goes wrong, and great illustration of flashlight test
https://www.thesamba.com/vw/forum/viewtopic.php?t=661445

Tue Oct 31, 2017 7:24 am

I read all the links you guys shared. Thanks.

My last attempt at syncing the carbs didn't go well. I set the speed and idle mixture screws as instructed but I end up with an engine that has no response to turns or the idle mixture screws. I'm assuming the carbs were running off the progression holes. It was also suggested for me to adjust the air bypass screws (I think Modok mentioned it in another thread) in order to get the RPMs up without having to expose the progression holes to do it.

I've yet to start it on this attempt as I'm waiting on a snail I ordered. Both carbs are at .003 and backed out one turn. No progression holes are exposed. Thanks for the great insight. Wish me luck!

Tue Oct 31, 2017 8:07 am

If you get no drop with the idle mixture screws, it means you have too much fuel being metered from elsewhere. This can be the progression holes, especially if the idle jet is too big.

It can also be too high a fuel level (wrong float level, too much fuel pressure, choke pistons leaking, or bad needle/seat).