Korman Triple Carb Conversion

[boonies]

@Stevehose , i noted in a zenith string you mentioned:

"based on experiments with a balance pipe system on my triples, I believe the smoothness comes from added slight richness with the pipe allowing residual mixture to be sucked in from the other manifold(s). I never confirmed it on Zeniths but did on the triples."

Do you connect all three manifolds together directly from manifold vacuum port on the carbs? I am interested to know if you think it smooths out some of the vacuum pulse signals.

I have the coupe running, not well yet though. I didn't have time to put the air fuel meter on, but I did put a vacuum gauge on the manifolds and have never seen anything so crazy. The bounce would normally indicate valves or head gasket. I did adjust the valves, but have no symptoms that would indicate a head gasket issue.

 

[Stevehose]

Do you connect all three manifolds together directly from manifold vacuum port on the carbs?

I linked all 6 vacuum ports together with T's and hose, I ended up not keeping this because with individual throttle bodies it tends to steal mixture easier from its neighbor(s), and you can dial in the mixture on each cylinder's manifold anyway which you can't do with the stock 2-carb manifolds/carbs, hence the "improvement" in idle quality there with a balance tube. So I scrapped it. If you want to use vacuum for a distributor advance, you can use # 3 & 4 cylinders, they are on opposite strokes so the pulse is smooth and mixture robbery minimized.

The bounce would normally indicate valves or head gasket

On individual intake barrels you're going to get a useless wild gauge reading unless you have a liquid dampened gauge, basically unreadable on the generic cheapo vacuum gauge we all have.

 

[boonies]

Well, I have a sun electric gauge, so not cheap (when new), but definitely not water dampened. Thanks as always, for your insight.

The engine is definitely running smoother than initial start-up which had some pretty wild popping back through the carbs. Definitely still a work in progress.

 

[Honolulu]

+1 on damping the vacuum signal, this can be done several ways, the simplest being to squeeze down on the vacuum tubes, or put in restriction device(s). The sizes of the restrictions won't matter unless one is grossly different than another.

Another "old style" way is to rig some clear aquarium tubing, filled with nice red ATF (engine oil would work too and help damp vacuum pulses b/c it's more viscous). One tube for each cylinder, all tee-d together. You'll still need damping restrictions. The height to which the oil rises is a direct reading of vacuum in whichever port it's connected to. Warning: if one intake is pulling a lot more vacuum than another, it may suck the oil right in. No harm done, it usually won't suck in enough to cause harm, but you have to shut down and refill the tubing and work out the bubbles. BTDT.

In the beemer world there was the Harmonizer, a device with pair of digital vacuum sensors used to synch carbs on boxer motors. Sadly the developer died before bringing to market a device for more than two intakes at a time. I had a 4-cylinder K100RS and used a borrowed Harmonizer from a pal with a R1150. Those tools are quite scarce now, but sometimes someone stepping up from the old bikes will surplus one off.

I would like to think that with six intake tubes, one could smooth things out by careful selection of which ones were linked. Again, proper restriction might be key to making it effective.

 

[daicos35]

On my triples, I run a mechanical advance distributor (no vacuum), and have removed the chokes. Less to go wrong... start up is lumpy for 2 mins... thats it. Am sure vacuum advance etc, may add some drivability at the margin, but i am vv happy.

 

[Drew Gregg]

My Korman engine has their intake manifold and the 3 DCOE 40 carbs, no chokes, and the 123 distributor. This setup has never seen cold weather since the car has been in Hawaii and South Florida since 2006. My trip to Highlands, NC recently had the morning temp at 49 degrees F. The car started right up and completed the 110-mile mountain tour with no problems. The start-up was pretty much the same as usual with the temps 20-30 degrees higher.

 

[boonies]

I have dcom’s and @Stevehose shared his jetting which I am using as my baseline. I have removed the chokes and installed the 123 distributor last week.

Valves adjusted, new plugs (have about 1,000 miles on new wires) and just replaced the coil with a Bosch red coil. I have an air meter, and also a carbmate, but don’t have the additional carbmate splitter for multiple carbs.

Hope to get the coupe on the air fuel gauge later this week If time and weather permits.

 

[daicos35]

Are you simply grabbing vacuum from one of the cylinders, or do you have a fancy interlinked set up?

Do you know if the 123 can be used without vacuum?

 

[Stevehose]

Do you know if the 123 can be used without vacuum?

Yes it can

 

[boonies]

@daicos35 , I am also using the 123distributor curve that @Stevehose shared on this thread (or a related thread). As Steve indicates, there is a no vacuum option for the custom distributor curves, and that is my approach for now as well.

Loading the centrifugal curves into the 123 is really very simple. I had a little trouble with the first start-up after installation, but it was all me. I had the distributor timing off slightly and needed to go back to TDC and align the distributor.

 

[daicos35]

interesting,, personally , with triples, no choke, mechanical advance eliminates a lot of the gremlins, and from my point of view doesn''t effect drivability or performance. I have a bosch mech advance unit. same diff to yours.. the carbs and distributor were jetted / set up on a dyno, by a mob down here, who mostly do road rally prep (targa tasmania) for classic cars. They swear by it.