Plugs foul on 1&3 only need help

[FreeBug]

What's the cam? The whole problem is the cam....

[Janne71]

[FreeBug]

Stock cam? Then maybe take a look at what VW did on later type 3 twin-carb engines: a balance port per intake valve?

I'm really intrigued, as twin-carb type 3s, with that cam, and tiny-plenum manifolds idled on all cylinders. But the pros who knows say that a bigger plenum is better. I'm confused; there is definitely some element of the equation I'm just not getting, probably several.

[oprn]

The one my sister had ('66) did have a bit rougher idle than my Beetle but I understand the cam was the same. I am thinking the difference between the Kadron idle and the VW Solex idle is carb size. Kadrons are 40 mm but the Solex are 30 or are they 32mm? I forget off hand.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[BlueBounty]

Ok folks here's what i have sorry for the sideways pics.
1776 Berg engine I built 10 years ago
I have a W-110 Engle Cam
I believe its 8.1 comp
Duel Kadrons rebuilt by Kaddyshack
Pertronix ignition
Blue Coil
Manx Exhaust

Fouled plug is from #3 and has maybe 2 miles on it its the upgraded NGK number but supposed to be the same as the older on .
Clean plug has 500 miles on it and has the older number on it.

Hope this helps. I guess I can always swap to a single carb but I don't have much space.

[oprn]

I believe Freebug is correct in saying that the cam has a lot to do with aggravating this inherit single throat/dual carb problem. I think the plugs are telling you the true story, you have one lean and one rich cylinder on each head.

I also see another problem. You have no temperature control on that engine and I would hazard a bet that it is running too cold. My Kadron equipped stock cam 1600 DP would not fire on the front two cylinders cold period! Even fully warmed up on the highway the front two would drop out when I stopped at a set of lights before the light turned green. These engines cool off that quick! Around town driving, it rarely ever idled on all 4. With or without the balance tube it was the same, no difference. I am talking about 70* F days here not winter by the way.

Then I sourced and installed the thermostat and flaps. The difference was remarkable in around town drivability. It still only idled on 2 cylinders on start up but after it was warm it only dropped the front two occasionally if idled for a while. Most of the time they stayed lit.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[Alstrup]

Maybe try and swap to non resistor plugs on all cylinders as no1 task. A wimpy blue Bosch coil will not handle resistor plugs very well.
Also, that exhaust is a - shall we call it a challenge. you can not rely on the AFR readings until about 22-2300 rpm with that one. Too much pulsing. You - can - cheat it by closing ½ - 2/3 of the outlet while testing below 2500 rpm.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[FreeBug]

[oprn]

What about more initial advance, say 14* BTDC? That is something I never tried.
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[Alstrup]

Correct. Sgl dual carb engines with more cam duration need higher idle timing. I did not recommend that because we knew too little about the set up until "now" 13-14 degrees is a good starting point, and especially with only 8-1 CR.

An engine with stock cam and Kads can - and should idle as a type 3. If it doesnt you have goofed up somewhere.
With sgl barrel carbs the rule of thumb is that the more valve overlap you have the larger plenum you need in order to keep the cylinders from making charge robbing. A balance tube can sometimes make it up for a larger plenum, but the "suction poiint" needs to be in the correct position. (Take a look at the Riechert Solex manifolds and you´ll see what I mean.)

Some people may disagree with me, but I have found that with cams a´la the W110 under dual sgl barrel carbs you need at least 60 mm from underside of carbs to the divider.

These manifolds were made for a 117 hp 1914 buggy engine. Split cam 284. 248/240 @ 0,050" 0,473"/,425" valve lift. on 110 LC. advanced 2 degrees. Puurs like a kitten at 900-925 rpm. and pulls very well from about 1300 & up with peak hp @ 5300.
Ohh, and NO balance tube.
Also, the rough texture is deliberate for best possible fuel atomization.

To further illustrate the matter. This below is a set of manifolds for 34/35 mm Solex PCI´s. The customer had built a street legal (In Austria) 2110 engine for his pre 60 car. But the engine didnt make power. It hovered around 100 hp. I got heads and manifolds up to try and improve them. I did some trial and errors to figure out where the restriction was, and a large part of it was not enough plenum. I made the plenum larger by some 30% I believe and along with a few other improvements like a better valve seat cut along with going from 37,5 to 38,5 mm intake valves to get a better throat relation I was able to increase hp to 115, with more torque everywhere.
On the flow bench the plenum increase was good for almost 15 cfm with nothing else done.

PS. One last thing. When you do this you want to make the center divider sharp like on the top pictures. The Solex manifold is actually too sharp, but I didnt know that at the time. It is better to have a little shoulder there to divide the fuel stream. Reason is, that you want the fuel to shoot off of the edge and back into in the flow. If it is sharp as in the Solex manifold the fuel has a tendency to devaporize and just slide down the wall and enter the chamber like droplets that are very hard to ignite, so you wohnt get much use out of it.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[BlueBounty]

So it seems like what everyone is saying is if I dont want to continue to mess with this setup, change everything out to a single carb set up. What does eveyone recommend for a duel port single carb? I'm tired of messing with this and I'm ready to bite the bullet and swap the kadrons out. I'm not looking for power or speed, I just want to putt around town reliably. Thanks for everyone's input.

[BlueBounty]

What are the chances that my valves are mis-adjusted causing this issue? Anyone?

[Janne71]

[Alstrup]