Any old school Carb Gurus ?
07-08-2005, 05:16 AM
#1
1.0 BAR
Thread Starter
Join Date: Apr 2005
Posts: 375
Any old school Carb Gurus ?
Have one small problem.
Cant understand what this gizmo on the carb does.
The local shops here rever to it as the power valve.
I know how a power valve on a bike works i.e. it uses suction to pull fuel direct into the carb. And has no pump.
This thing has a pump that squirts some gas down the primary buterfly every time you blip the throtel. It also has a diaphram connected to the arm.
THe problem is if I hook up the vacum line like the factory book recomends it blows the little rubber diaphram. What would happen if we just didnt hook up a line to it.
Basiclly what is it. How does it work. How will it seeing a boost signal effect it.
Cant understand what this gizmo on the carb does.
The local shops here rever to it as the power valve.
I know how a power valve on a bike works i.e. it uses suction to pull fuel direct into the carb. And has no pump.
This thing has a pump that squirts some gas down the primary buterfly every time you blip the throtel. It also has a diaphram connected to the arm.
THe problem is if I hook up the vacum line like the factory book recomends it blows the little rubber diaphram. What would happen if we just didnt hook up a line to it.
Basiclly what is it. How does it work. How will it seeing a boost signal effect it.
??
07-08-2005, 08:59 AM
#3
3.0 BAR
Join Date: Sep 2004
Posts: 1,588
Re: Any old school Carb Gurus ?
Carbs work just like you said, off of vacuum to pull fuel into the engine. That little pump gives it a little extra shot when you first step on the throttle to keep the engine from falling on its face. Your vacuum lines need to see vacuum, not boost. If you're hooking them up and getting boost, your carb won't work worth a ----. You need to draw a line pre turbo so you get vac, not boost.
07-08-2005, 01:43 PM
#5
1.0 BAR
Thread Starter
Join Date: Apr 2005
Posts: 375
Re: Any old school Carb Gurus ?
Ok this is what I could figure after asking arround and playing with the setup some.
Your right about one thing. Its a little pump that squirts some gas when I press the accelrator so the engine wont fall flat on its face. So far in agrement.
That lever preses up against a rubber diaphram with a metal piston in the center and squirts gas. Lever is directlly connected to buterfly shaft on throtel plate.
There are two tubes in the pic. The silver one is the fuel return line the brass one is where you hook up your vacum refrence.
Now what does that vacum refrence line do. This is where we are stuck right now.
Somebody said it helps pull the diaphram back. I tried blowing thru it. And sucking on it nothing. If I disconect the vacum line and put a gauge in to it. With or without boost no air movement.
Even without the vacum signal line hooked up to it. It still squirts gas every time I hit the pedal.
So I just ran the car for some time with nothing hooked up. It seems to be working ok. No leak, no blown gaskets and boosting ok to 15 PSI.
So till somebody can confirm what it is. Ill just leave it unconected as the car dosent seem to mind and is runing fine.
If its only job is to squirt its squirting with or without the vacum line.
Or maybe what I could do is hook it up like the factory says but run a check valve so it only sees vacum never boost.
Your right about one thing. Its a little pump that squirts some gas when I press the accelrator so the engine wont fall flat on its face. So far in agrement.
That lever preses up against a rubber diaphram with a metal piston in the center and squirts gas. Lever is directlly connected to buterfly shaft on throtel plate.
There are two tubes in the pic. The silver one is the fuel return line the brass one is where you hook up your vacum refrence.
Now what does that vacum refrence line do. This is where we are stuck right now.
Somebody said it helps pull the diaphram back. I tried blowing thru it. And sucking on it nothing. If I disconect the vacum line and put a gauge in to it. With or without boost no air movement.
Even without the vacum signal line hooked up to it. It still squirts gas every time I hit the pedal.
So I just ran the car for some time with nothing hooked up. It seems to be working ok. No leak, no blown gaskets and boosting ok to 15 PSI.
So till somebody can confirm what it is. Ill just leave it unconected as the car dosent seem to mind and is runing fine.
If its only job is to squirt its squirting with or without the vacum line.
Or maybe what I could do is hook it up like the factory says but run a check valve so it only sees vacum never boost.
Heres where im lost 
07-09-2005, 02:10 PM
#9
1.0 BAR
Thread Starter
Join Date: Apr 2005
Posts: 375
Re: Any old school Carb Gurus ?
On a lark we tried to colapse the float bowl. Went upto 45 PSI which was the max the pump being used could make and it still didnt colapse.
The carb has the following vacum lines and this is what Ive done
1. Vacum line to large diaphram which is used to open the secondry buterfly valve. Took this off. Conected it to the FMU with a 1 way valve.
THe second buterfly is now direct linkage. With a link plate. Made in Bliet. I have 3 plates to try. One opens both buterflys together equally. One opens the primary 50% and then opens the secondry over the remaining 50% of the action left on the primary. And one opens the primary 90% and then the secondry over the remaining 10% of movement on the primary.
2. Vacum line from carb to valve in air filter box. (Sealed off)
3. One vacum line goes from bellow the the throtel plate to the signal line in the pic above Havent decided what to do with this yet.. But it gets a one way valve for sure.
4. Vacum line under the gizmo which used to go the DIstri. Now goes to BOV.
5. Vacum line from manifold now goes to the distri.
Usin the manifold to distri helps cause it has the strongest vacum and the strongest boost. So when accelrating it allows me to set my idle timing at 10 deg.
With Vacum it goes upto 40 deg. WHen boost starts it starts pushing the timing back till the timing settles at arround 20 Deg at 10 PSI.
Most vacum lines Ive hooked up with a one way chk valve.
Except for the Distri and Bov.
Today I took the car out on a longish trip with this gizmo line unhooked.
On the way back it stoped.
Had to call the service station and tow truck etc.
The mechanic who came said you have to hook it up. Cause it is the vacum line that acts on a piston and this controls flow back down the return line. THink about it. If the squirting is working with or without the line hooked up. Why did they give it. ANd sure enoughf behind the ruber diaphrams that handle the squirts there is another diaphram with a metal piston which is hooked up to the fuel return line.
Since we had put a spring in the other day for the WG. Boost can go upto 20 PSI if I floor it.
Dont know whats hapend but my fuel pump has packed up.
With the fuel pump on I dont see any gas coming into the FMU or carb if hooked up direct. Time to drop the tank and check it out.
But
1. You are right. It does reduce the shot when cruising. That is if the diaphram is hooked up.
All the points you guys made are valid.
Except for this new pice of info that has confused me totally. i.e. its needed for the fuel return line to work. Maybe the fuel return line wasnt working this caused the fuel pump to overstrain and packup. Dont know
Sorry for the long post. No car. Nothing better to do. Well actually better go drop that tank and pull the pump.
The carb has the following vacum lines and this is what Ive done
1. Vacum line to large diaphram which is used to open the secondry buterfly valve. Took this off. Conected it to the FMU with a 1 way valve.
THe second buterfly is now direct linkage. With a link plate. Made in Bliet. I have 3 plates to try. One opens both buterflys together equally. One opens the primary 50% and then opens the secondry over the remaining 50% of the action left on the primary. And one opens the primary 90% and then the secondry over the remaining 10% of movement on the primary.
2. Vacum line from carb to valve in air filter box. (Sealed off)
3. One vacum line goes from bellow the the throtel plate to the signal line in the pic above Havent decided what to do with this yet.. But it gets a one way valve for sure.
4. Vacum line under the gizmo which used to go the DIstri. Now goes to BOV.
5. Vacum line from manifold now goes to the distri.
Usin the manifold to distri helps cause it has the strongest vacum and the strongest boost. So when accelrating it allows me to set my idle timing at 10 deg.
With Vacum it goes upto 40 deg. WHen boost starts it starts pushing the timing back till the timing settles at arround 20 Deg at 10 PSI.
Most vacum lines Ive hooked up with a one way chk valve.
Except for the Distri and Bov.
Today I took the car out on a longish trip with this gizmo line unhooked.
On the way back it stoped.
Had to call the service station and tow truck etc.
The mechanic who came said you have to hook it up. Cause it is the vacum line that acts on a piston and this controls flow back down the return line. THink about it. If the squirting is working with or without the line hooked up. Why did they give it. ANd sure enoughf behind the ruber diaphrams that handle the squirts there is another diaphram with a metal piston which is hooked up to the fuel return line.
Since we had put a spring in the other day for the WG. Boost can go upto 20 PSI if I floor it.
Dont know whats hapend but my fuel pump has packed up.
With the fuel pump on I dont see any gas coming into the FMU or carb if hooked up direct. Time to drop the tank and check it out.
But
1. You are right. It does reduce the shot when cruising. That is if the diaphram is hooked up.
All the points you guys made are valid.
Except for this new pice of info that has confused me totally. i.e. its needed for the fuel return line to work. Maybe the fuel return line wasnt working this caused the fuel pump to overstrain and packup. Dont know
Sorry for the long post. No car. Nothing better to do. Well actually better go drop that tank and pull the pump.
