syncronizing zenith carburetors with vacuumMate

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cory cotherman
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syncronizing zenith carburetors with vacuumMate

#1 Post by cory cotherman »

sorry if this is a dumb question but I don't have my zeniths in front of me and was wondering if there was a vacuume port that I could hook up my vacuumMate syncronizer tool up to? If your not familliar it's a really great tool for multiple carbs. just got done breaking-in my engine and now need to sync the carbs. would love to use my vacuumMate as it's extremely accurate and easy to use as long as one can hook it up to a vacuume port.

http://tecmate.com/products/vacuummate/

thanx cory

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David Jones
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Re: syncronizing zenith carburetors with vacuumMate

#2 Post by David Jones »

Don't think so Cory. I use one of these. Cheap and reliable and simple. I made up an adapter to use it on Zeniths. A large circular piece of 1/8" steel with a thin piece of rubber sheet glued to one side so it will seal on the carb top. The synchrometer then sits happily on the metal surface and seals itself. My Zeniths idle at 4 to 5 Kg/hr.
Search the web for a good price, any where from $30 and up.

https://www.amazon.com/Carburetor-Synch ... B00SLH03R4
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Ron LaDow
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Re: syncronizing zenith carburetors with vacuumMate

#3 Post by Ron LaDow »

Cory,
I presume the port needs to be below the butterflies? What do those things cost; I can see various ways of getting a port in there.
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Re: syncronizing zenith carburetors with vacuumMate

#4 Post by John Brooks »

I agree with Ron. If you really positively just have to use a special and expensive tool, you will need to have an adapter made to go between the carb and the aluminum manifold. You could machine one from micarta, plastic or metal or maybe 3D print some. Some late 912's had a small port for vacuum advance, I have used that with a motor cycle vacuum gage.

Seems like a lot of work and certain expense to replace a unisync
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Ron LaDow
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Re: syncronizing zenith carburetors with vacuumMate

#5 Post by Ron LaDow »

John, you could easily drill a port into the manifold at the mounting 'boss' and make it 'plugable', not a product Pre Mat could sell, but not hard to do. This assumes the port must be below the butterflies, which question has not yet been answered.
I do really like the idea of seeing the flow of all four holes displayed at one time, but what does that thing cost?
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cory cotherman
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Re: syncronizing zenith carburetors with vacuumMate

#6 Post by cory cotherman »

yes below the butterflys. They are expensive around $560 I got a used one for about $300 (ebay) I would not go out and buy one just for this but I happen to have one already and wanted to use it. Drilling and tapping the manifold sounds like the way to go. The vacuumMate comes with screw in adapters. Then the holes can be plugged. Cool thing is...it reads the pulses and has a tach feature too, as well as reading all 4 cylinders independently.

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cory cotherman
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Re: syncronizing zenith carburetors with vacuumMate

#7 Post by cory cotherman »

drilled and tapped my vacuum ports. works perfectly.
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Ron LaDow
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Re: syncronizing zenith carburetors with vacuumMate

#8 Post by Ron LaDow »

Late C engine?
I like the fact that you can tune them with the filters on; removes one more variable.
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Re: syncronizing zenith carburetors with vacuumMate

#9 Post by Jim Liberty »

Cool indeed. The first time I've seen this.
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Re: syncronizing zenith carburetors with vacuumMate

#10 Post by Dick Weiss »

John,

The '68/'69 912 engines have vacume retard distributors, NOT vacume advance.

Dick

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Re: syncronizing zenith carburetors with vacuumMate

#11 Post by C J Murray »

I'm all for trying something different but I don't see the point. Unlike a motorcycle you can't equalize all 4 throats with an easy adjustment. You can't equalize the barrels on an individual Zenith carb unless you carefully twist the throttle shafts and I wouldn't want to do that as a part of regular tune-ups. Using a Unisyn is easy and gets very good results.

Ron, to get a vacuum reading at idle where imbalance is a bigger problem it must be sourced below the throttle.
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Re: syncronizing zenith carburetors with vacuumMate

#12 Post by Neil Bardsley »

Ron LaDow wrote:Late C engine?
I like the fact that you can tune them with the filters on; removes one more variable.
You can always use Jack Stagg's suggestion of removing the leads from the distributor cap and noting change in idle. Might be a bit cheaper/easier?

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Re: syncronizing zenith carburetors with vacuumMate

#13 Post by Harold Singh »

David Jones wrote:Don't think so Cory. I use one of these. Cheap and reliable and simple. I made up an adapter to use it on Zeniths. A large circular piece of 1/8" steel with a thin piece of rubber sheet glued to one side so it will seal on the carb top. The synchrometer then sits happily on the metal surface and seals itself. My Zeniths idle at 4 to 5 Kg/hr.
Search the web for a good price, any where from $30 and up.

https://www.amazon.com/Carburetor-Synch ... B00SLH03R4
Any photos of this adapter plate in action? Maybe some dimensions you could share?

Thanks,
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Re: syncronizing zenith carburetors with vacuumMate

#14 Post by Steve Proctor »

Dellortos and perhaps Webers have adjustable bypass ports that route mixture around the butterflies, allowing precise flow adjustment of individual cylinders and would make this device useful. It would seem that, used on older carbs, it would let you know that the balance between cylinders is on or off with only butterfly tweaking available as a remedy, whereas used on the newer carbs, it would allow bypass port adjustment to remedy.

That said, would the device be useful in mixture adjustment to achieve the highest vacuum for each cylinder?
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Re: syncronizing zenith carburetors with vacuumMate

#15 Post by Dave Erickson »

Dick Weiss wrote:John,

The '68/'69 912 engines have vacume retard distributors, NOT vacume advance.

Dick
Except for one thing. Vacuum retard usually takes a vacuum port *above* the throttle plate. For some bizarre reason, Porsche put a vacuum retard distributor along with vacuum ports that sense full manifold vacuum. So John's point is valid, you can use the vacuum ports on a late 40PII for tuning, or even to install a 123 distributor with the vacuum advance feature.

-Dave

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