Twin 40 carbs
19-03-2017, 04:50 PM
#1
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Twin 40 carbs
Hi,
just a quick question, I am currently running a 2.0 pinto on twin 40 carbs in a sierra.
i have read that you shouldn't (don't need) use a dizzy with vacuum advance? I have piped mine in but can't get it running right, it idles ok but feels like it's dropping a cyl down the road. Where I have piped vac in is on the back carb.
so do I need to get a dizzy without vac advance on it?
cheers
just a quick question, I am currently running a 2.0 pinto on twin 40 carbs in a sierra.
i have read that you shouldn't (don't need) use a dizzy with vacuum advance? I have piped mine in but can't get it running right, it idles ok but feels like it's dropping a cyl down the road. Where I have piped vac in is on the back carb.
so do I need to get a dizzy without vac advance on it?
cheers
19-03-2017, 04:55 PM
#2
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Can you not just block off the vac pipe?
19-03-2017, 05:12 PM
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19-03-2017, 06:40 PM
#4
If your dizzy has a vacuum advance, then it would make sense to use it.
Should run smoother and be better on fuel at constant speeds with it connected.
I'm not sure that the vacuum signal from one carb will be smooth enough though.
One trick that MegaSquirt users do is to drill each inlet and join all 4 vacuum signals together - then add a moped fuel filter between the ECU and signal to act as a damper and smooth the signal out.
You might find that your timing is jumping all over the place with it plumbed into one port !
Should run smoother and be better on fuel at constant speeds with it connected.
I'm not sure that the vacuum signal from one carb will be smooth enough though.
One trick that MegaSquirt users do is to drill each inlet and join all 4 vacuum signals together - then add a moped fuel filter between the ECU and signal to act as a damper and smooth the signal out.
You might find that your timing is jumping all over the place with it plumbed into one port !
19-03-2017, 06:55 PM
#5
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If your dizzy has a vacuum advance, then it would make sense to use it.
Should run smoother and be better on fuel at constant speeds with it connected.
I'm not sure that the vacuum signal from one carb will be smooth enough though.
One trick that MegaSquirt users do is to drill each inlet and join all 4 vacuum signals together - then add a moped fuel filter between the ECU and signal to act as a damper and smooth the signal out.
You might find that your timing is jumping all over the place with it plumbed into one port !
Should run smoother and be better on fuel at constant speeds with it connected.
I'm not sure that the vacuum signal from one carb will be smooth enough though.
One trick that MegaSquirt users do is to drill each inlet and join all 4 vacuum signals together - then add a moped fuel filter between the ECU and signal to act as a damper and smooth the signal out.
You might find that your timing is jumping all over the place with it plumbed into one port !
Its got a outlet off one of the carbs which I've used for the vac advance, I haven't gone into the inlet manifold directly onto the carb,
i might still disconnect the vac advance pipe tomorrow and bung it up and see what happens. I do have a non vac dizzy somewhere
19-03-2017, 06:57 PM
#6
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The car would be nicer to drive, easier to set up and better on fuel with throttle bodies.
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19-03-2017, 07:09 PM
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I kind of didn't want to spend much more on the set up I've got, was hoping to get it running somewhere near for this summer, then winter I am thinking of turbo. I'll mess with the vac pipe tomorrow, do people agree that the vac pipe shouldn't just go to one carb then? It connects to cyl 4 carb at the moment
21-03-2017, 10:50 AM
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Been messing with it further, done a compression test, all very slow to rise and only reach max 75 psi, which is half it should be.
I have a P100 engine but will that be slow?
I have a P100 engine but will that be slow?
