Balancing Webers/Airbox

[stuartgb100]

I used to run twincams in Cortinas without an airbox, so this question never arose back then.

Is their a question of the webers going out of balance once the airbox is fitted (particularly the rear weber being restricted when drawing air)?

ie you balance the webers with the airbox off, then adjust mixture, idle etc and finally the airbox is fitted. Does this alter the balance appreciably?

I have an empty, standard airbox with a 4 inch hose down to a big K&N filter in the nose.

Regards,
Stuart.

[1964 S1]

I believe yes, there is a difference with the airbox on. The outer cover can be re-worked so it's deeper at the rear than in stock form, allowing better air flow. The rear carb can starve, you can check your plugs for clues.

[cliveyboy]

This is why I recommend using a "Carbtune" four column manometer.
It screws directly into the carbs , meaning you can balance the system under load through the airfilter and airbox.
It also takes under two minutes to fit .
Clive

[stuartgb100]

Clive,

I plan to do the same, but from what I can see, it means the head off to drill the tappings - unless you advocate drilling insitu?

Regards,
Stuart.

[rgh0]

The imbalance in the carbs due to the restriction caused by the standard air box on No 4 cylinder will only become signficant at full wide open throttle and high revs where you have maximum total air flow through the engine.

The balance adjustment done at idle will have no influence on this imbalance as the throttle are wide open. The only way to fix it is a deeper modified air box or run without the air box and use oil impregnated foam socks with the correct non flammable oil in them over the intakes.

regard
Rohan

[cliveyboy]

Stuart
I can only speak about my Dellortos which have 5mm screws on the top that you undo and screw in the adaptors for the manometer tubes to push onto.
The Carbtune also came with 6mm adaptors which they state are for Webers.
Perhaps some one with Webers can enlighten us.

Clive

[vikebo]

I have got a carbtune, but since I got the engine back in the car just recently, I have not tested it yet.

Anyway, it seems like my webers have got pipes where the hoses to the carbtune can be connected after removing the blanking screws at the ends.



I do not think I have seen these pipes on other webers so this may not be of any help...

Eivind

[lotuselan2]

There are very short air horns for Webers and Delorttos. Do these help with #4 air flow at high throttle openings? If so, should you ift all four or just on #4?