Dual Weber IDF 40's lacking top end power

[Brentonodon]

So went through and cleaned them again to check to make sure there wasn't something obvious that was causing me to not get the full punch out of these two. Noticed that the fuel color in the float bowls was noticeably different. Any thoughts on what would make the one side so much darker? I took these photos to show that the float bowls were metering the fuel to a pretty equal amount so they were taken after taking the carbs off and avoiding spilling as much as possible. There were about 4 pumps of the throttle to check the pump jets functionality.

[Brentonodon]

Decided it was time to get some proper info to help dial in this beast. Ordered up an AEM wideband A/F gauge and Bosch sensor.

Installed it all up. Realize now that I've got to move the bung to angle the sensor downward to keep schmutz from building up and fouling the sensor.

[pullstart]

That 4 into 1 collector being slip fit might scavenge air and muck up the reading of the a/f gauge... not speaking from experience but from what I see.
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4 seater Appletree buggy, road legal with 002 IRS, 3x3 Appletree kit, 6" over Dan's beam with 10" towers and Fox 2.0 shocks, '00 Subaru EJ25 with KEP stage 3 clutch and KEP adapter plate.

my build page: https://www.thesamba.com/vw/forum/viewtopic.php?t=662104&start=0

[Vanillagurilla]

I've been looking at throwing a wideband in mine as well but I'll wait to see what readings you come up with. I have almost the same motor that's acting the same, seems to really fall off at 4500rpm even though I can feel the cam come on around 2200. 1835 dual hpmx 40 carbs, 135 mains, 52 idles, 50 pump and 200 air, 110 cam and empi gtv-2 stage one cnc heads.

[Multi69s]

[Brentonodon]

As soon as I can get some time available I'm going to move the sensor to one of the exhaust pipes coming from a single cylinder on each bank. That way I can see what, say cylinder 2 and 4 are doing. That will allow me to see float bowl information and get the jetting right on at least those two cylinders and just set up each barrel of the carbs the same.

[pullstart]

[Brentonodon]

New bungs installed! Sniffing cylinder 3 I'm seeing it still pretty rich practically everywhere except when I'm barely touching the throttle off idle. Ordered some 45 idle jets and 130 mains along with a sync tool to be doubly sure everything is where it needs to be. I've got a sneaking suspicion that when I'm touching the throttle the left carb might not be pulling at the same rate as the right side which could lead to that lean state I think.

Here's what I've got in there so far.
1915cc
dual port heads - not sure on valve sizes as I haven't had them off yet
engle 110 cam
28mm venturi
F-11 emulsion tubes

jets currently are as follows
50 idles
135 mains
200 airs

Things I'm seeing.
after doing LBI I'm chilling at about 13.5 on the AF gauge
just a hair off throttle, like barely touching it, cylinder 3 is shooting lean around 15
once I'm up into the 1000-2000 rpm range I see about 12.5 on the gauge.
when the mains come in it doesn't really change a whole lot. Might make it to 13.

Will update you all this weekend on how it changes with the new idles and mains.

[Vanillagurilla]

I have an 1835 and almost the same jetting except my idles are a 52, I bet mine is pig rich especially when I take it to the high desert. What altitude are you at?

[Brentonodon]

Right on. I'm in SF so right at sea level. Maybe a few hundred feet.

[Brentonodon]

Ok. Feelin a bit like a dingus. Put in the 45 idles and cruised around a bit. After warming up I adjusted for LBI and got the idle smooth. Was pulling a bit over 1000 rpm and the sniffer showed 11.2 or so at idle. Scratched my head for a bit as I'd read on the wideband results thread that I should be looking for somewhere around the low 14 high 13 range at idle. Then I got out the ole trusty tuning light and low and behold, the possible cause of all this frustration, my timing was WAY out. Like 20 deg! So I go to loosen the distributor pinch clamp and discover it's already loose so I've set it back to 8 deg at idle for now and tightened it back up. Readjusted for LBI and there it was, the magical upper 13 reading I'd been looking for.

For the life of me I couldn't understand how people were getting such clean data from their AF setups. I believe it's much more possible when your timing isn't all over the map. This might also explain the one good day of running like a bat out of hell then back to normal the next. Geez. Decided to call it quits at 10 to keep on good terms with the neighbors. More to come this weekend as the saga continues.

[Vanillagurilla]

So the 45 idles were the ticket? Can i borrow your afr gauve and probe when your done? Haha. I'm curious now what mine is running. Probly in the 10-11 range at idle. How does yours star when the motor is cold? Mine spits and chirps out if the carbs untill it warms up, sometimes it won't idle when it's cold and if it does it's around 450 rpm.

[Multi69s]

[Vanillagurilla]

[Brentonodon]

Alright. So I tried out the 45's, that led to some super lean running and popping and stalling when trying to take off after a stop. Back to the 50's which are definitely a bit rich. Thinking it might be time to order some 47's. Wish they weren't $7 a pop but oh well.

Today I put in the 130 mains to see if I can't at least get the main circuit closer to dialed in. Funny thing is that it didn't seem to change anything. That got me thinking maybe my floats were off on their adjustment. Pulled them, dead nuts at 10mm. I'm wondering what effect fuel pressure has as it's the one thing I haven't checked yet. I can imagine that higher fuel pressure pushes the inlet needle to the float bowl harder which would fight the "floatyness" of the floats, allowing more fuel in the bowl than the set height. Any thoughts on that?

I'm going to chase down a fuel pressure gauge this week. In the meantime, also ordering some 47's. The saga continues.

[Vanillagurilla]

If fuel pressure was the problem you would either run out of fuel in the bowls after a pull or it would flood at idle.

[74 Thing]

You need to verify fuel pressure before starting the tuning process since if it is off it can cause multiple symptoms.

Verify fuel pressure (tee in a temporary vacuum/pressure gauge)
Verify floats are set correctly
Verify timing
Valve adjustment
No exhaust leaks
Linkage adjusted correctly

[Brentonodon]

Won't let this thread die just yet.

Did check fuel pressure. Is a steady 5psi.

After a long while of mucking with it I decided to swap out the heads. Now it's got panchito 044s on it. After going through it all it sure is breathing better at the top end.

200 airs,
135 mains,
50 idles

I feel like there's a little more to go through on the timing but that'll come.

[oprn]

Yes your down links should be at the same angles. Viewed from the rear they should be perfectly vertical. From the side it may not be possible to get them vertical but they should at the very least be identical angles.

As for the dirt in the idles issue, they sell tall idle jet holders as a "fix" but the REAL issue is your air cleaner elements. They are junk! Especially for an off road car with exposed tires/carbs. At the very least they need to be oiled but better yet they need pre-filters.

The first time I took mine off I was horrified at the volume of road dust sitting on the top of the carbs! Those filters only stop rocks, sticks, low flying birds and small woodland critters! Everything else sails right on through! My wife sewed up some pre-filters out of flannelette diaper material, I oil them and the original filters and not a bit of dust gets through now. No plugged jets going on 2 years!

I ended up with 47 idles on my 1910 cc engine. If you are running rich mid range larger vents could help perhaps by delaying when the mains come in. I am running 31mm vents in mine. Others here have more experiance with these carbs than me.
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[L5wolvesf]