twin 40's help

[SR-Rally]

started fitting my 40's today at the garage. going back monday as busy tomorrow but could really do with finishing them just one question?

there going on a tuned 1300 with a vacum advance dizzy, where does the vacum pipe connect on carbs? or shud i make a T piece on brake sero vacum pipe? can't see place for it on the carbs.

if any one has any other advice or thing i mite have to do let me no, i'l list what done so far

Lowered alternater
re run water coolant pipes
using oil catch tank for breather
sorted throttle linkage
i re jetted the carbs to a base setting so will run well enough to get on rollers :)

[Adam]

You dont need the vacuum advance, just leave it open on the dizzy

[SR-Rally]

explain? i've heard this befor but surely when engine is idling it will be fine but when reved or hot not? not saying your wrong:) just like to no why it not needed with 40's but is standard:D

[Adam]

Its not "needed" as standard, it just alters the ignition timing, increasing the revs slightly on idle. It does nothing apart from when the engine is idling (under vacuum)

I never ran one on my 40d 1400, and a lot of others dont either. :)

[SR-Rally]

thanks adam :thumb:

[paul james]

Isn't the vacuum advance a specific thing to the sport carbs, and normal weber 40's don't have them.

[Adam]

Yup

[SR-Rally]

so what does the vacum advance actually do? sorry sound thick i assumed it was so ass engine reved the spark kept in time?

[Adam]

When the engines idling it changes the ignition timing slightly to give a smoother/higher idle..
Thats all.

Just set the idle speed on the carbs, job done :)

[SR-Rally]

thanks again. learn something everyday :P

[Stuart]

vacuum tends towards 1Bar (bearing in mind less than 1Bar = vacuum in earths atmosphere) as the throttle opens, so vac advance is only used at idle.

[SR-Rally]

finished fitting the dellortos today, they sound amazing and it goes well considering only had basic setting up :D going on rollers in next week so see how she fairs.