Plugs foul on 1&3 only need help

[BlueBounty]

I cant seem to fix this issue. I have a 1776 with duel Kadrons rebuilt by I pro builder. I'm running Compufire with a vacuum advanced 009. I have the carbs jetted and set with a fuel ratio meter. My problem for ever is it runs great until the plugs on #1 & 3 foul. Then of course is starts sputtering and back firing. 2 & 4 look great. I can't seem to figure this out. I could see maybe an adjustment problem on one of the carbs if the fouled plugs were on the same side but this not the case. Can anyone help me out on where to go next?
Thanks

[Ohio Tom]

real common issue with dual-single barrel carbs like Kadrons.

Magnified when you go with a hi-po camshaft.

Can usually be managed by adding a balance tube from one manifold to the other.
Your manifolds likely have fitting bosses in them already.

Try to use 3/8" or 1/2" hose.

It should "help" your problem.

[Dauz]

those things idle on two cylinders. The balance tube like Tom mentioned should help

[oprn]

I always get a chuckle out of engines that run great but...

I suspect it's not, and has the same 2 cylinder idle/4 cylinder run mid range and up that I too had when running Kadrons. I played with them with a balance tube and without and quite frankly just wasted time and effort. If I got a good synchronize on the carbs it would run virtually identical with the balance tube on or blocked off. The best I ever got it was a 4 cylinder fast idle coming off a hard run that would drop back to 2 cylinders as the engine cooled off before the lights turned green again.

What that made the most difference of all the things I tried was to put the thermostat and flaps back on so that the engine ran warmer around town and at a more consistent temperature all around. Very hard to tune one that is hot - cold - hot - cold especially with Kadrons on it.

I was at a VW event 3 weeks ago and after talking to a Beetle owner about his Kadrons (he assured me that his did not have this problem and ran perfect) I listened to his wife idle it around the parking lot and out onto the street... on 2 cylinders and heard it clear up and catch the other 2 as she drove away!
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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)

[jimmyhoffa]

What is your idle ignition timing, cam, and compression ratio?
_________________
1974 Chenowth 2RL #1244 Street Legal
My other car isn't ridiculous.

[Alstrup]

[BlueBounty]

Thanks folks for the info. Let me gather the specs and post some pictures and maybe we can figure this out or I might just go to a single carb for reliability but my bounty hunter does not fair well for that as it has a overhang on the back and not much clearance. Stay tuned.

[Vanapplebomb]

Cam will be the biggest factor in if you can get the mixture evened out on those dual single barrel carbs with a balance pipe. As duration goes up, and overlap increases, the vacuum signature changes in the manifolds, and the balance tubes effectiveness drops off like a rock. On stock to mild cams, balance tubes can work wonders.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[mark tucker]

also plug type and heatrange.have the plugs been heat range checked to see if they are right or not??

[earthquake]

I wonder what effect a 1" spacer under the carbs would have? it would give you a little more plenum area. Kinda like putting a open bore 1" spacer on a V8 with a dual plane intake manifold, it kinda makes it act more like a single plane manifold.

eQ
_________________
74 CLASS 11 LOOK-A-LIKE
69 DUNE BUGGY
79 INTERNATIONAL SCOUT II
05 SCION XB SERIES RELEASE 2[#437]
95 Chevy C3500 dually
98 Ford E150
Link to Kelly J. Nolte 3/20/53 - 11/6/08
https://time-zonelabs.blogspot.com/p/about-kelly.html
DEATH TO CHINGERS!
[From a military recruitment poster in the novel "The Stainless Steel Rat" By Harry Harrison]

[Lingwendil]

Why not just increase the effective plenum area under the carb by porting the split further down? Assuming you run aluminum manifolds. Alstrup recommended this to me and it was relatively easy to do with a burr in a die grinder. It's supposed to help things a good bit.
_________________
73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[Alstrup]

I´m still waiting on engine details. Until we get that there is no telling what would be the best approach.
That said I agree on the plenum
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[Ohio Tom]

The problem is a fundamental design issue.
The firing order on a VW motor is un-even on each side.
First cyl 3 draws a charge in, then 4 air in, then a big pause as 1/2 side draws air.
So with any performance cam, 3 is still drawing air it, when 4 starts.
This robs 4 of some charge. Enough that it won't hit at idle.
The 1/2 side has the same issue.
So you get the 1/3 idle thing.

A balance tube can help to stabilize the vacuum, much like a plenum would.
The problem with plenums is always the same. It's a band aid to mask a poor manifold design. Plenums have to be jetted around and they usually suck fuel.

It is for this reason, you won't find may dual/singles on my motors.
I find it much easier and smoother running to just install a set of dual IDF's.
they actually run smoother and get better fuel economy.

[earthquake]

OK, how about putting two Kadrons on a IDA manifold on each side of the motor?

eQ
_________________
74 CLASS 11 LOOK-A-LIKE
69 DUNE BUGGY
79 INTERNATIONAL SCOUT II
05 SCION XB SERIES RELEASE 2[#437]
95 Chevy C3500 dually
98 Ford E150
Link to Kelly J. Nolte 3/20/53 - 11/6/08
https://time-zonelabs.blogspot.com/p/about-kelly.html
DEATH TO CHINGERS!
[From a military recruitment poster in the novel "The Stainless Steel Rat" By Harry Harrison]

[madmike]

Only if you build the linkage
_________________
'Black Ice'Drag Buggy 'Turbo'
Rail Buggy 1915 turbo
76 Drag/Street bug 2180cc 'Turbo' 11:85 @113 mph"If I go any faster I'll burn up the Hamster" ,gets 28 mpg. also 10/09/22 11.90 @115 mph
"If I'm ever on Life Support,UNPLUG Me, Then Plug me back In see if that Works"

[j-dub]

[Janne71]

[oprn]

The only 2 carb set ups that don't have this mixture imbalance in my limited experiance is a single center mounted one or give each cylinder it's own carb barrel. Even the stock twin singles were somewhat this way.
_________________
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)

[Janne71]

[modok]

the notch at the intake gasket surface is for single carb manifolds IMO.

Properly shaping the plenum area right below the carb is more important for this type of carb setup. You PROBABLy want to make sure it splits evenly both sides. The fuel also should IN THEORY come straight out the lower hanging side of the throttle and you can look at the manifold and think about where that is going to go, what it will hit.
Weird plug fouling without any other cause can often be traced to liquid gasoline dribbling into one cylinder or another. It could be a manifold problem or a carb problem. Float level is too high causing the main nozzle to drip, or acc pump squirt mis-aimed it can run just fine but still be fouling plugs. I don't know which is more likely the problem but these units do have a reputation of having problems with both.