Author Topic: Balancing Dellortos & Webers  (Read 4825 times)

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Offline EuropaTC

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Balancing Dellortos & Webers
« on: Saturday,October 13, 2012, 09:23:41 AM »
I'm sure the older hands here will already have either got one of these tools or at least have heard of them, so this is for anyone new to a car with twin weber or dellorto carburetors.  I recently saw a thread on Lotuselan.net praising this little gadget, and as I was fiddling about trying to get my Europa to run a little smoother (like it used to do in those rose-tinted days) I thought I'd give one a try.

So what is it ? Basically a small plastic gizmo that you stuff into an open dellorto trumpet and measure the airflow, thus allowing you to balance the carburetors with some degree of accuracy.  It's a more scientific method than the old idea of placing a length of tubing in each trumpet, listening to the noise the airflow makes and adjusting so they are all the same.

Does it work ? Yes, and far better than I'd ever imagined. After removing the airbox I had exactly the same readings on all trumpets within a minute of starting the engine, it really is that fast.  I followed the instructions about revving and allowing to settle (what you'd do anyway) but even so the whole job was over much faster than I've ever managed it before.

What was surprising was that I'd thought they were about right anyway having used my previous Gunson adaptor & manometer to set them up the previous week, but this gauge identified a slight imbalance which really has made the engine feel a touch smoother.  I think this is due to the fact the Gunson set-up relies on you holding the adapter in place while reading the gauge and making adjustments  whereas with this it holds itself in place and the readings are much steadier than the manometer tube.

Is it worth it ? I paid £40 delivered ($60 ?) which is a lot for something that is made of plastic and feels a lightweight tool. So in terms of tool for your buck, it's not impressive. But in terms of efficiency, doing what it says on the tin and time saved I must say I don't regret one penny of the purchase price.

They are sold in many outlets (including the dellorto website) and at varying prices so it's worth shopping around. It's not an essential purchase because if you have mechanical sympathy then I think you can do the same job by feel and observation, but if you struggle with balancing carbs after so many years of fuel injection systems, then it's a good tool for your workshop.

The pictures show the item, how it fits on the car when you're balancing the carbs and finally my previous method which does work but takes longer.....

Offline Bainford

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Re: Balancing Dellortos & Webers
« Reply #1 on: Monday,October 15, 2012, 04:56:08 AM »
Thanks for the info, Brian. I have purchased two types of balancing devices, though haven't tried either one yet. I'm replacing my entire fuel system, including carbs, this winter so I'll be up to here in carb tuning before long. I have seen this type of balancing tool online and was curious about its effectiveness. Sounds as though it works quite well. Do you know if this unit can be used on Stromberg carbs?
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline EuropaTC

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Re: Balancing Dellortos & Webers
« Reply #2 on: Monday,October 15, 2012, 08:42:04 AM »
Yes, I think you'd be ok with this on Strombergs. There are 2 models (possibly more ?) but the one I got  was the SK and advertised as for use with  40/45/48''s SU/Stomberg/Solex carbs. They vary wildly in price over here so worth shopping around. One thing that is cute is that it gave typical air flow rates at idle (e.g. webers 1-3kg.m3) which is an additional pointer to you getting them set up correctly.  I thought mine was ok before but must admit it's better after tweeking with this, it's very smooth now, almost like a proper car.....    ;)

Brian

Offline Bainford

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Re: Balancing Dellortos & Webers
« Reply #3 on: Monday,October 15, 2012, 11:31:07 AM »
Cheers Brian. Thanks for the info. I'm going to look into one of these.
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline 3929R

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Re: Balancing Dellortos & Webers
« Reply #4 on: Tuesday,October 16, 2012, 08:14:34 AM »
Is yours an easier to use alternative to this type of balancer?

Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: Balancing Dellortos & Webers
« Reply #5 on: Tuesday,October 16, 2012, 09:19:32 AM »
Is yours an easier to use alternative to this type of balancer?

I can't honestly say because I've not used (or seen) that type of instrument before.  I assume you get a reading on the tube comparable with the air flow/vacuum created in the carb inlet and hold it in place while you take readings ? 

If so, then the principle is the same as my previous manometer set-up which gives a floating pointer in the orange manometer tube in the last photo I posted. Nothing at all wrong with that approach and in truth I've used it myself for a long while.   The manometer is graduated and so you can get a numerical reading to compare chokes, and that's what I have done before.

The advantage I found with this is that it's not reliant on me holding it in position to make a seal, it just pushes into place.  I think that's why it was so steady in operation and that made it easier to take readings.

There wasn't a lot of difference when tested with this new gizmo, one carb was 3kg/h and the other just over 4kg/h. When I'd set it up before I'd aimed for identical manometer readings and so the differences can only be down to me not making an identical/efficient seal on all the chokes because the tubing/manometer is the same for all.

I guess my main gain from this gizmo has been that it makes a DIY mechanic look better by removing the operator-induced error !   :)

Brian

Offline 3929R

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Re: Balancing Dellortos & Webers
« Reply #6 on: Tuesday,October 16, 2012, 03:28:28 PM »
Thanks for the explanation.  I inherited an old balancing tool that I think looks like the one in my post but I've yet to use it.  Balancing my carbs is still on the to do list.
Mark
Salt Lake City, Utah, USA

Offline Bainford

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Re: Balancing Dellortos & Webers
« Reply #7 on: Wednesday,October 17, 2012, 04:25:03 AM »
Is yours an easier to use alternative to this type of balancer?


This Uni-Syn tool is one of the types that I have. I'll try to remember to take a picture of the other type if anyone is interested. I haven't tried either one yet, but I'll be giving them a try this spring when I install my new carbs.
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline Bainford

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Re: Balancing Dellortos & Webers
« Reply #8 on: Friday,November 09, 2012, 01:23:02 PM »
As promised, here are a few pics of the Synchrometer carb balancing tool.












It's a bit difficult to see when placed in position on the carb, but with decent lighting it is easily read. Better perhaps than the photo suggests. I didn't realise it at the time, but these devices can be bought in calibrated pairs so that both can be fitted to the carbs at the same time for real time comparisons. I bought mine at JC Whitney.
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline EuropaTC

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Re: Balancing Dellortos & Webers
« Reply #9 on: Friday,November 09, 2012, 11:12:18 PM »
Now that looks a nice bit of kit. 

In fact I 'd guess that it's and earlier (read better engineered) version of the one I showed. Looking at the instruction sheets with the optional adapters and the name "synchronometer", they look very similar to the sheets that came with mine. They have the same name for the tool, similar adapters and the only difference seems to be that mine show more modern carburetors.  (no SU type)

Brian

Offline StrawberryCheesecake

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Re: Balancing Dellortos & Webers
« Reply #10 on: Friday,May 22, 2015, 03:18:06 PM »
I've used one of those 'snail' type synchrometers on my 914-6 conversion on triple choke IDAs. Made the job a lot easier, and well worth the money you save compared to paying someone else to balance your carbs. I found that if the idle is uneven to start with, it's better to go round the chokes at least twice - once to get them roughly in the same place, but the engine speed will change as you adjust. 2nd time is fine tuning, helped by the smoother idle to start with.

Offline jbcollier

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Re: Balancing Dellortos & Webers
« Reply #11 on: Friday,January 22, 2016, 10:24:31 PM »
The cheap and readily available Uni-Syns are overly restrictive and affect the engine's running while being used.  They briefly give an accurate reading and then the engine filters and the reading falls.  I have one and it is very useful for holding your repair manual open to the right page.

I have found the Synchrometer to be the best when syncing Webers and Dells.  It has a dampened movement and has no effect on the engine's running.  It takes just a moment or two for the reading to fully stabilize.

I use an undampened, vintage air flow type for syncing SUs and Strombergs.  Again it doesn't affect the engine and gives instantaneous readings.  This works well in the typical Strom/SU set up with two/three cylinders per carb and a balance tube.  It doesn't work well with one-port:one-carb set-ups as the pulsing reading is difficult to decipher.

Multi-carb set-ups with difficult access and/or individual cable actuation, have me using a set of matching, dampened vacuum gauges designed for motorcycles.  Cheap ones are nasty but the good ones are well worth the expense making syncing carbs without a solid linkage easy.
« Last Edit: Saturday,January 23, 2016, 07:35:22 AM by jbcollier »

Offline 4129R

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Re: Balancing Dellortos & Webers
« Reply #12 on: Saturday,January 23, 2016, 01:01:01 AM »
Just bought one on eBay for under £37.00 including postage.

Ticking over at 2000+ RPM when hot is not good.

I timed the engine using a strobe and that cured the backfiring. I just hope this can make the engine run smoothly.

A completely new top end was very expensive, new cylinder head, valves, cams, and 40DCOEs so the fine tuning is needed to make the investment worthwhile.

Offline EuropaTC

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Re: Balancing Dellortos & Webers
« Reply #13 on: Saturday,January 23, 2016, 01:19:47 AM »
A completely new top end was very expensive, new cylinder head, valves, cams, and 40DCOEs so the fine tuning is needed to make the investment worthwhile.

Ouch !  with that sort of expenditure you deserve a bargain....    £3 cheaper than in my post !

If it's of any interest, I wrote that first post a long while ago and during that initial spell with the tool I set up both the Elan & Europa (Weber & Dellorto). Both have pertronix ignition so that aspect is reasonable stable but the good news is that I haven't touched either car since and both still idle at ridiculously low speeds cold (no choke) and around 900 when hot.  I'm pretty much convinced it was the accuracy of the gizmo rather than my imaginary mechanical genius that got the carbs right.

Brian