help with 1.4 sr twin carb opening flaps

[merv beckett]

hi i race a 1.4sr nova and wanted alittle more power out of it and one thing someone said is make both flaps on the carb open at same time instead of one first then other once trottle wide open. can this be done or is it a lie cheers

[Dave A]

Yes it can be done. A lot of the Hot rod boys do this, but won't tell you how! I bought one in the end and used the bits to mod my own carb. Basically it has the vacuum actuator removed. A spring to pull open the 2nd choke as soon as the cam off of the main choke lets it. The spring needs to be adjusted so that it has a very low tension at the initial opening point, or the choke wont close properly, tick over at 4k results!!

[merv beckett]

ok cheers mate i can see where you coming from ive got a spare carb il see what i can do.

[marc69]

I tried doing this with mine, nearly blew up the engine when the 2nd barrel stayed open idling at over 8000revs.

I put the safety lug back. However I did find a way to get more power by plugging the vacuum advance for the ignition into the vacuum at the 2nd barrel. It opens everytime your foot is flat at 3500rpm and over rather than gradually at over 4000. All the time I am on the track I am over these revs. If you can find a bigger vacuum (i got one from an astra carb I think....) then it should open fully at 3500 and if you are below 3500 with your foot down you should actually feel the car lurch.

Also make sure that the wee curled pipe actually does throw fuel in and isn't partially blocked.

Hope this helps.

[merv beckett]

I tried doing this with mine, nearly blew up the engine when the 2nd barrel stayed open idling at over 8000revs.

I put the safety lug back. However I did find a way to get more power by plugging the vacuum advance for the ignition into the vacuum at the 2nd barrel. It opens everytime your foot is flat at 3500rpm and over rather than gradually at over 4000. All the time I am on the track I am over these revs. If you can find a bigger vacuum (i got one from an astra carb I think....) then it should open fully at 3500 and if you are below 3500 with your foot down you should actually feel the car lurch.

Also make sure that the wee curled pipe actually does throw fuel in and isn't partially blocked.

Hope this helps.
is the curled pipe pointing in the second barrel if so do i need to rev motor upto 4000 before seeing fuel go into that barrel or should petrol go into 2nd barrel as soon as you put on the gas also feel the car lurch, what does that mean sorry never heard that word before lol

[marc69]

That is the pipe but the fuel is pulled through by the vavcum created by the 2nd brrel being open so you can't do it idling as you'll over rev your engine, the foot has to be completely down to move the throttle saftey bracket bit. I removed this bracket and almost wrecked my own car.

The way i tested it was with a permanent marker and torch. Put some ink on the second throttle butterfly. Drive the car full throttle with the pipe off the vacuum at the 2nd barrel or, just take the clip off the linkage. In other words drive the car without the 2nd barrel being able to open.

Check with torch that the pen marks are still there. Then connect it all up, drive like a nutter again at high revs with the foot flat.
1. you should notice if it drives faster
2. Check with a torch, if it all works the ink should be cleaned off by the petrol.

Lurch as in you should feel the car move with the additional boost of the 2nd barrel.

[merv beckett]

cheers mate il give that a go