Kadrons - Increasing Ported Vacuum Signal

Not sure if I am helping here but when I sent mine off to be ported for vacuum they only ported one side - said that was all that was needed. I have never had a problem w/ mine since and all works well. How about temp blocking the weak one and just using the vacuum from the strong carb and see if that works. Just a thought - hopefully someone else will have other ideas as well.

When installing the Kadrons I didn't touch the dist. Before install timing was 30 degrees vacuum advance disconnected on the 34PICT3. Nothing changed other than my Kadrons not being able to generate a strong enough vacuum signal.  Was getting a 40 degree timing advance total with vacuum on the PICT.  My question is whether the Kadrons are capable of generating a vacuum signal of at least 8 in. Hg.  Any input would be appreciated.  Thanks.

If you don't get the info you need you could always contact Jeff at the Kaddie Shack.

http://kaddieshack.com/

 sounds like te hole isant in the right position  or has a leek to another gally.with that said I have no clue about any cadog carb.but if done corectly the carb will have plenty of signal as did my 2 4 bbl carbs on top of my tunnel ram on a small block.itis a simple function of the carb if it's done corectly,not realy engine size related for the most part. but if you had put on true duels (40 idf style)it would run better and get beter mpg,make more power in the entire rpm range. might want to make sure you did the mod corectly.some have a angled cut tube sticking into the throght for a better signal, but like I said I dont do kadogs.(it does sould like the port is to low)

I always thought the vacuum port vented beneath the butterfly in the carb.....  This is the area with the highest vacuum at idle and decreases as the throttle is opened...  With a common connection in the carb, between a hole below and another above the butterfly, the   vaccum signal will be "diluted" and probably not strong enough to "get the job done"....

"I self-installed the ported vacuum tubes as many have described and illustrated (i.e., by blocking the below-the-butterfly hole of 2, very carefully removing the caps in the carbs covering the ported vacuum openings, blowing everything out to confirm the openings were open to the hole of 2 above-the-butterfly, then installing brass tubes using a little JB weld to seal around the outside)."

I went back and re-read this paragraph and it doesn't make any sense at all, even though I haven't seen these instructions and illustrations.  If you're tapping in to the carb throat ABOVE the throttle plate you'll get almost NO vacuum signal.  All of the vacuum occurs BELOW the throttle plate ( unlss the throttle is wide open and then only a small signal).  The holes ABOVE the throttle plate (and there are often two or three of those, arranged vertically, each about 1/16"-1/8" apart) are transition ports which assist the carb in supplying the proper amount of fuel mix for the throttle plate position as it opens up and are activated only as the edge of the throttle plate passes up past each hole and, as the hole transitions below the edge of the plate, gets a vacuum signal to draw additional fuel from the bowl into the intake manifold.

Unless I totally don't understand Kadron carbs (but I thought they were, basically, updated Zeniths which I'm familiar with) I would suspect that you're trying to get a strong vacuum signal from the wrong side of the throttle plates.

"Ported vacuum" means the vacuum port is just above the throttle plate at idle. This turns off the vacuum advance of the distributor at idle so you don't have excessive timing. When you crack the throttle, the port is uncovered and timing advance kicks in improving throttle response.

My understanding is that the bottom of the 2 ports (i.e., the one below the butterfly) is manifold vacuum, and manifold vacuum will provide you with vacuum signal at idle, which is something that you don't want for properly operating your SVDA distributor and why the lower port is blocked off.  You want a vacuum signal under load when the butterfly is cracked open.  Like the 34PICT4 advance port, there is no vacuum from it at idle.

I got the flat spot out of my Kadrons on my 71' bus by stretching the advance spring in my 009/making sure the accel pump tubes were not too far down in the venturi/adjusting the accel pump rod to squirt instantly/ran a bigger idle jet. You are trying to smoth out the transition fueling,you can do that with more fuel in the idle circuit. 

as usual justin knows what he is talking about. and gt has a good idea.

  below the throttel plates is manifold vacume, above them is ported vacume, where the port is and the type will determan how much and when it starts pulling vacume. and it will usualy pull more than the manifold vacume does. as manifold vacume decreses with load&throttell opening the ported increases.

 like I stated I know nothing about those carbs, you may or may not have them ported corectly, from the sound of it you dont.

 working in the performance end of things for most of my life I have a lot of expearance with a lot of diferent carbs, modifying,jetting,adding extra circut and more. I have however never messed with a vw carb of any kind,and the only single bbls carbs were either single for each cylinder , or single for a single cylinder.

The latest on this adventure is that I broke down and bought a vacuum/pressure guage from Harbor Freight ($20).  The best $20 spent.

 

I discovered that one of the Kads (on the driver's side) was putting out a spiky vacuum signal under throttle blips that would repeatedly hit about 8 to 10in. Hg.  The Kad on the passanger side had a similar spikey signal but was only able to pull around 2in. Hg.  The vacuum signal going to my SVDA dist from teeing from the 2 Kads was a stable 3in. Hg and no greater regardless of the revs (i.e., not enough to budge the vacuum advance)

 

I decided to plug the vacuum port on the low Kad and connect my dist directly to the higher vacuum signal Kad on the driver's side. I went for a test drive and suddenly my SVDA is working and life is wonderful.  No more 2,500 to 3,000 RPM stutter. 

 

I got so spoiled with how the engine responded and behaved having the extra advance runing with my 34PICT3, I was beginning to regret my move to the dual Kads.  But now I can really fell a sense that the engine's breathing has opened up.  Revs to 4,500 quickly and effortlessly.  Next stop will be ratio rockers.

 

Thanks for all input and advice.

 

Grant

 

My explanation for this is that the higher vacuum This makes sense to me as the

 

only

Glad that worked out for you. I did an install of dual Solexes on a sand rail a few years ago, got everything from John at aircooled.net. SVDA worked great with one ported vacuum line. Only one carb is needed for the signal and I was going to suggest that but you figured it out!

I would double check the carb with the incorrect vacuum reading as this could indicate a leakey base / manifold gasket.....  Just a thought....

I thought that might work - glad it worked for you - now on to driving.

Yes, it seemed that with my teed arrangement the carb with stronger vacuum signal would suck air through the carb with the lower vacuum signal, bringing the total signal down to the weakest of the two.

 

Now I found another issues that is with my distributor that has come to light.

 

Thanks Grant