Can anyone help please...... My friend put a new motor into his manx, it's a 1916cc motor with Kadron carbies and Empi manifolds. The engine is running flat on cylinders 1 and 3 when idling. There is plenty of spark..... The engine seems to run fine on full speed, just seems to be flat when idling. Any assistance would be greatly appreciated
Hmmmm....does it have a balance tube fitted??? Sounds like there might be a slight air leak.When started from cold,can you touch the extractors on cylinders 1 and 3??Do they get warm/hot at idle like 2 and 4?? Just curious how you determined they were not firing.👍
Baja Wes wrote:This is fairly common. The VW engine likes to idle on the rear two cylinders, especially with Kadrons.
Wes, sorry mate, pardon my ignorance, but "what the" ??? I'm not doubting what you're saying, but I can't for the life of me figure out why/how that would occur
I noticed it a little when I ran a stock carb, and more so when I ran kadrons. I figured the reason was this;
The VW firing order is 1432. Which is also 4-3 then 2-1. Basically the pairs of cylinders on each side fire in order.
So look at the drivers side kadron (cylinders 2 and 1);
* Air/fuel goes into cylinder 2 for 180 degrees of crankshaft rotation,
* immediately after air/fuel goes into cylinder 1 for 180 degrees of crankshaft rotation,
* then you have a whole 360 degrees of nothing,
* then air fuel goes into cylinder 2 again and the process repeats.
The same thing happens on 4 and 3.
So basically cylinder 2 starts the air moving in the carb. Because the air needs time to accelerate, cylinder 2 initally doesn't fill very well (at low revs like idle).
Then as soon as #2 intake valve closes, #1 intake valve opens. So now cylinder 1 fills really well because the air is already moving in the carb from cylinder 2 filling.
Then #1 intake closes, nothing happens for 360 degrees and the air flow in the carb stops.
This effect means #1 and #3 get a better intake charge at idle, and I think a slightly richer mixture than #2 and #4.
yep perfect sense - mine does the same (only idles on two - smoothly, but u can take a plug lead off and it makes no difference) and has done for about 15 years!
Very common knowledge that kads idle on 2 cyl a bit, especially with a bit of cam.
Playing around with venturies, and jetting can help sometimes, but its nothing to worry about.
Do your dell's have dedicated manifolds to the twin ports or do they swirl it so each pot can grab from both barrels?
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When your running dual webbers or Dell's each cylinder will have its own carby throat (They are not linked). Therefore the issue wes mentioned no longer exists........
I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!
BiX wrote:When your running dual webbers or Dell's each cylinder will have its own carby throat (They are not linked). Therefore the issue wes mentioned no longer exists........
Thanks Bix....
Eggzeckrly what him said.... plus i realy dont think Kads on a 1916 would give it full potential....
Expensive? not really.... i think Empi was trying to sell a set for like 275 bucks... even if you had to get manifolds and stuff you would get out if it for less than 500 buks... worse case..
You could recover that easy with the sale of the Kads.
How big is your cam, I had a similar problem with a 1916cc, 120 engle cam, sounded like a mack truck at idle.
Fixed the problem with a single 48 ida (which popped a little), then went to twin dells. Can't beat them for value and response (smooths the engine right out).
