Carb balance readings

[unity1]

I balanced my carbs the other day.  Firstly I'll say I discovered the balance was a fair way off and in doing so improved the low level pull and smoothness.

 

The question I have is does the actual vacuum level matter as the reading were way down on previous times. For the last 20 years its been around 26 however this time which is the first time I balanced them after a carb rebuild they are around 16. Would it suggest that I have an air leak or something or am I just over thinking.

I've attached some images from 2004, 2018 and the last balance. Don't worry about the actual alignment they are in align and wobble so a photo still has some imbalance.

 

[eeyoreish]

As far as i’m aware the actual value doesn’t matter as long as all the air flows are balanced to the same level. IIRC correctly (it’s a while sine i last did mine) following the manual procedure you are only balancing one inlet per carb against the other. Then balancing one carb to the other. Hence the actual values don’t figure.

Edited July 13 by eeyoreish

[drdoom]

The overall vacuum will vary considerably due to throttle position at idle, due to the individual throats configuration. I'd have thought 26" rather unlikely in any case as it approaches absolute vacuum, 16 more reasonable though I have no figures of my own to offer.

[unity1]

Yes it is correct that you balance each pair and then adjust the connecting bar to align them and if necessary the idle. I actually did a guide almost exactly 20 years ago now.

https://www.unity1.co.uk/Lotus/Project/Engine/Tunning/tunning.htm

To be honest the car is running better after I just balanced them. It was more that I've had the car for over 20 years. I would balance them often along with usual checks after the winter. The vacuum level has always been around the same. You can see form the images from 2004 and 2018 the level were more or less identical. The sad thing is 2018 was the last time I did it. Family life, Covid, yada yada..

This is the first time I'd balanced them after the carbs being rebuilt last year before all the body and interior renovation. I've also had the tops off several times recently due to fuel issue and then sheered balance banjo bolt after repainting plenum/turbbo/diffusor.  Its more the uncommon change leading me to question it and myself and wondering if I need to be looking elsewhere for a potential or due fault.

[910Esprit]

Yes, I agree they look low, but probably not a major issue as you can still get them all balanced.  If its the same as a G turbo, there is one common rail that feeds vacuum to the brake servo and the controls reservoir (that little black thing that sits on one of the fuel tanks).   Just temporarily disconnect and block the 2 unions that supply vacuum to these 2 accessories.  If your vacuum is restored, one of them is likely to be leaking.   Could also be that the common rail is also leaking where it connects to the manifold, or it may be something else all together!        

[unity1]

@910Esprit Thanks I shall look into that.