The Synchrometer Is Here! What do I do with it?

Well the Sychrometer arrived with the Kadron adapter. Ok, that's all I know except that I have to remove the air cleaners and put it on the carbs to measure the air draw.

What is the ideal measurement in kg/h?
What rpm do I want to try to achieve and how do I set that?

I guess these few questions should start a nice discussion.

Rich
Naples, FL

Hi Rich; all I can tell you is that the VW Service Manual indicates the idle rpm's for a stock engine should be around 800 to 900. I wonder if it's the same for engines with dual carbs, etc.

OK, Rich, let's see.

I use a Unisyn - it's the same as a Synchrometer, but looks a bit different. The Synchrometer must have an adjustment method to "baseline" it - someone else on here should be able to tell you how to do that if you don't have instructions. Basically there is something you turn or adjust to set the Synchrometer meter for a "baseline" reading that you'll then compare against.

If you're running basically a stock 1600 dual port and all that's been done to it is adding dual Kadron's, then this adjustment should be reasonably straight forward.

First, the Synchrometer. This is a device that measures air flow down through the throat of the carb. That's all it does, but having that ability allows you to balance all four cylinders so that they're all working the same amount. Balance is important, otherwise the engine will run roughly, especially at idle. When you first use it, you must adjust it for a "baseline" reading. That means that you place it on a carb velocity stack, notice the reading on the Synchrometer and adjust it such that it's reading about 1/4 scale (say, 3.0 ). Remove it and you're ready to start testing.

First, run around the block a few times to get the engine up to temperature, stop the engine and then remove the air cleaners. You should see a couple of little, vertical, trumpet cones sticking up on the top of each carb. Those are velocity stacks, and they guide the air into the throat of the carb. The Synchrometer should fit nicely onto one stack at a time.

Disconnect the linkage from one carb only (doesn't matter which one), then re-attach it but only finger tight.

SEVERAL WORDS OF CAUTION HERE. We're going to be working on a running engine with an exposed fan belt and several spinning things that can seriously hurt you. Take your time, and steadfastly avoid anything moving, like the fan belt. It can really hurt you. 'Nuf said.

Start your engine and let it idle. Disconnect that carb's linkage again (you needed it connected to get it started, right?) and it should stay idling.

Focus on the carb still attached to the linkage. Place the Synchrometer on a stack and notice the reading. Now, adjust the air mixture screw (that little Brass Screw on the side), on that barrel only, for a maximum reading on the Synchrometer. Once attained, move the Synchrometer to the other stack and do the same for that stack. They should come pretty close to the same maximum reading. If you run off scale (high) then re-adjust your Synchrometer to bring it back down to mid-scale or so and keep going.

Once both barrels are adjusted for max flow, go to the other carb and do the same thing to both of those stacks. Again, they should be pretty close to each other, BUT THEY MAY BE SLIGHTLY DIFFERENT THAN THE FIRST CARB - That's OK for now.

CONTINUED IN NEXT POST >>>>>>

Now, note the reading on that last stack you max'd, and return to the first carb. Put the Synchrometer on the rear stack and note the reading. It may be higher or lower than the other carb. If it's lower, it means THAT carb is drawing less air than the other side, i.e. it's idling slightly lower than the other side. Find the idle speed screw for that carb and turn it IN to increase the Synchrometer reading to match the other side. One of two things may happen - it may begin to idle a bit smoother and/or it may increase in idle speed. If it is higher than the other side's reading, then turn the idle speed screw OUT to bring it down to match the reading from the other carb.

Note your idle speed. It should be between 800 and 1,000 RPM. ANYWHERE in that range is fine - it's all in what sounds good to you. If it is too high or low, you'll have to walk the idle speed up or down by turning each idle speed screw in turn 1/8'th turn until you get them to where you want them and then re-check side-to-side to re-balance left-to-right. You now should have all four cylinders balanced AND your idle balanced as well. Time to re-connect the linkage - I can smell the Beer Reward now! - Onward!

You can stop your engine now......

Dual carb linkages are adjustable separately on both sides with little turnbuckle ends on the linkage. All you have to do now is make sure the linkage is adjusted for the disconnected carb. Lift the linkage end up, and straighten it to line up with the hole on the throttle actuator. If it looks like it'll go straight in, congratulations, you lucked out. If it looks a little high or low, you'll need to loosen the locknut and spin the head either up or down to match the actuator hole such that it'll go straight in. Once there, re-tighten the lock nut, attach the linkage, tighten it up and you're done.

Remove the Synchrometer, return the air cleaners, clean your tools and Synchrometer, put everything away and go have a beer, you've earned it. Better yet, take it out for a spin and go get an ice cream or something........

Hope this helps.........gn

The synchrometer is simply to get both carbs running the same idle setting. pinch the crossover tube with vise grips. Remove linkage. Set idle screws so both carbs are using the same air flow.

lowbugget.com has detailed instructions for tuning the Kadrons.

Felt I should correct one aspect of Gordon's great response (sorry Gordon!); the Kadron's only have a single barrel in each carb, not two. (Unlike the more usually used weber IDFs)

The good news is that there only half the work to do to balance the Kadrons :)

Eric is right that the lowbugget.com site has great advice for setting up your Kadrons.

Setting up with the flowmeter is the way to go - mine were initially way off each other when I initially set them up by ear (causing popping on the overrun).

Wow. Overwhelmed with info. Thanks much, Gordon for taking all the time to give such detail. Indeed I noted that mine has only one throat per carb. Also briefly checked out the lowbugget site which has good info.

I need to digest all this. I think for tonight I'll just take the Synchometer out to the garage and let it acclimate. It has no adjustment or leveler by the way. I will also raise the engine lid and look at all those brass adjustment screws. Then I'll have a beer just to celebrate the adventure.

Rich

I mentioned the initial baselining because I use a Unisyn tester. It does the same thing, but has a little vertical tube in which slides a little plastic float in place of your meter. It also has an adjustable restrictor in the bottom to allow use with different draft carbs. People generally feel that the Synchrometer is superior to the Unisyn, from what I've read, but mine has been around since Moses wore Cowboy Boots and I'm used to it.

Obviously, I'm also used to dual barrel carbs, as Simon mentioned (thanks for the help, Simon!) - multiple Strombergs (from my street rodding days), Dellorto's, Webers and such. They all pretty much act the same.

Take the Synchrometer out to the garage tonight and just play with it so you'll know how it acts, then it'll be easier when you get down to business. Using one of those makes carb mixture and idle set-up a snap.

Hey, guys! I went to lowbugget.com and he writes it is a waste of time and money to try to sync your carbs, "better to do it his [sic] way." I take it his way is the new distributor he sells? Anybody go that route? I'm too much of a newbie to get that technical.

Rich

Rich:

I, too, went to lowbugget.com and found it to be a rather tedious web site to navigate. The information is there, but he really makes you work to find it (or maybe I'm just getting old!)

His recommended way of tuning carbs is the way I learned to do it 40 years ago - by ear, without a gauge. Now listen, everyone's ear is different and each can be imprecise. What I hear an engine doing is not always what YOU might hear it doing. Basically, he starts an engine, disconnects the carb linkage from BOTH sides and then adjusts the mixture screws while listening to the hiss of the air past the venturi's. If you're good, (and you do it a lot) you can get a carb tuned to a gnat's ass that way and do the same for idle speed left to right, just by sound. To be honest, after I tuned everything with my Unisyn, I went back and fiddled some more with my head between the carbs listening to each side and "Blipping" the throttles on each side to hear what they did. This is all fine if you know what you're listening to, but if you don't or aren't sure of what you hear, then the Synchrometer takes the guess work out of the equation.

After visiting his site, all my Kadron memories came back - the equalizer tube between manifolds ('cause they expect to see a plenum'd manifold - that's why they work so well with vacuum advance distributors), the single barrel on each side (I actually started with dual Solex 28's way back when, and they had similarly equalized manifolds), the cranky linkage (Hey! It was 40 years ago!). But they ARE good carbs, easy to understand and work with and they give pretty good performance.

All a carb does is atomize fuel into an airstream. Changing the air/fuel mix causes the airflow to change subtly and you can either hear it change (or THINK you heard it change) or see it registered on a meter. If you ear isn't trained well, which would you prefer to do?

You've already got the Synchrometer, and it'll work just fine for you. After you've set your carbs up and played with them for a dozen or so times (not because they'll NEED the attention, but because you're curious) then you can start tuning them by listening to the noises they make. By that time you'll be looking at the color of the spark plugs to set your mixture, too. In the meantime, get started with the Synchrometer.

gn

oh....and in respect for Simon's help, make that Beer a Guinness!

Only ONE more addition to Gordon's Post(s) . . .

Gordon, when's the book on how to tune multiple carb engines coming out?

AFTER you try the various adjustments, always 1/8 turn at a time, you have to WAIT! Sometimes a full minute. The Kadrons have big bowls and pretty large jets for the venturi size and it really takes a little while for the subtle changes/adjustments to manifest. Don't rev the motor at any point either, you'll just have to wait even LONGER for the extra gas from the accelerator pump to work it's way through.

If you give the adjustments time to adjust the carb, not just the screw position, you'll have a more info to work with. As Gordon also mentioned, these are very simple single throat carbs. They DO work great, but everything has to work in concert. The jets, the venturi, the vents (if you had them installed), the adjuster screw position . Change one thing you will have to consider the rest. We nearly baked our drag motor because the cam profile was too aggressive for the venturi/jet sizes. The motor ran great until 5000 then fell flat. The Kads were running out of fuel/ mixture, going lean and just cooking everything as a result.

Look at everything as a system and that system as a part of enother. Can't just turn one screw.

LUCK!!
TC

So what exactly is a Venturi?

Haven't had the time yet to use the new Sync but all the info is percolating in my head. Plenty of beer, though.

Rich

Rich, some of the info posted here is wrong. Get someone that knows how to sync carbs to show you how.

I read George's post and that got me thinking, so I went back and re-read mine and thought, "Shoot!" What was I thinking? (and it wasn't even in the middle of the night!!)

It's fruitless to try to use a Unisyn or Synchrometer to set idle mixture. You can do it and it'll work, but it is much easier to simply get the car idling well (with the equalizer tube connected for dual Kadrons), then turn the idle mixture screw in on one side until the engine slows down or stumbles, then turn it back OUT 1/4 turn or so as it smooths out again. Once one side is set, do the same for the other side - in 'til it stumbles, then out 1/4 turn or so.

THEN use the Synchrometer/Unisyn to balance both carbs left to right. This balancing can also be done by ear or "feel" (as the old timers do) but, again, if you're not used to doing it, then use the gauge.

Thanks, George, for seeing that.....you're a gentleman, too.....