Ram air operation

[dwm9ersfan]

I think I know how the sequence of operation is but could someone confirm the operation of the vacuum ram air

 

[tony-muscle]

The RAM air flappers are normally open without vacuum. So when driving around or at idle there is vacuum generated so the flappers are closed. When you hit the gas, vacuum drops and so the flappers open.

 

[jscott]

I put in an electric operated vacuum switch so I can open or close mine at will.

 

[tony-muscle]

I put in an electric operated vacuum switch so I can open or close mine at will.

I did the same. Great idea to control it on your own. I open the flappers driving in the highway and I can see drops of up to 15 degrees in the incoming air - when hot out. I have EFI so I can see that measurement live.

 

[swice]

Hi, my ram air 351c engine is "air starved' as the vacuum does not drop fast enough to open the flappers causing a brief stall when I punch down, any ideas?

 

[Don C]

Block off the vacuum lines so the flappers are open all the time, to make sure it's not your carburetor. When the flappers aren't open the carburetor has plenty of air available through the snorkel.

 

[swice]

hey many thanks, the snorkel is vacuumed controlled as well, I blocked it off ( to keep it open) and the problem of stalling was much better, but not completely. I checked the ram air vac line down to be sure it was exiting the manifold, still puzzled.

 

[mrgmhale]

Hi, my ram air 351c engine is "air starved' as the vacuum does not drop fast enough to open the flappers causing a brief stall when I punch down, any ideas?

I am betting the Ram Air is not causing the hesitation or g on heavy acceleration as you initially hit the throttle. That sounds more like a fuel starvation issue. I am assuming you are using a carburetor, not EFI. If that is the case there are a few places you can look at. For some carbs there is a accelerator pump actuating arm that has two linkage holes in it. The outer hole is used if you are able to do so with no hesitation issues upon acceleration. If you fuel demands are higher than "normal" you can move the actuating rod to the inner hole to get faster actuating with more travel when the throttle is flipped open. Another possibility it the accelerator pump diaphragm or plunger (depends on carb type) is leaking (internally or externally). I have also seen where debris gets into the fuel bowl and ends up having crud bock the accelerator pump jets. If the float level is too low it can also cause a hesitation.

Anyway, I would look at that kind of stuff before trying o solve the issue with Ram Air behavior. FWIW, if you leave the vacuum motors unplugged the flaps will remain open all the time - but be sure to plug the vacuum hose ends at the vacuum motors so the intake manifold does not end up with a vacuum leak.. It is what I do, but I also do not drive in the rain <g>...

 

[71ProjectJunk]

I am betting the Ram Air is not causing the hesitation or g on heavy acceleration as you initially hit the throttle. That sounds more like a fuel starvation issue. I am assuming you are using a carburetor, not EFI. If that is the case there are a few places you can look at. For some carbs there is a accelerator pump actuating arm that has two linkage holes in it. The outer hole is used if you are able to do so with no hesitation issues upon acceleration. If you fuel demands are higher than "normal" you can move the actuating rod to the inner hole to get faster actuating with more travel when the throttle is flipped open. Another possibility it the accelerator pump diaphragm or plunger (depends on carb type) is leaking (internally or externally). I have also seen where debris gets into the fuel bowl and ends up having crud bock the accelerator pump jets. If the float level is too low it can also cause a hesitation.

Anyway, I would look at that kind of stuff before trying o solve the issue with Ram Air behavior. FWIW, if you leave the vacuum motors unplugged the flaps will remain open all the time - but be sure to plug the vacuum hose ends at the vacuum motors so the intake manifold does not end up with a vacuum leak.. It is what I do, but I also do not drive in the rain <g>...

Agree with mrgmhale, the stumbling/stalling issue is not because of the ram air being closed. Most probably, as stated by megmhale, it has something to do with the accelerator pump circuit in your carburetor, or with the timing being retarded, or maybe just a vacuum leak making the engine run lean. Post what carb you have and maybe we can help.

 

[Precision Transmission]

What carburetor are you running, Swice?

 

[swice]

I am betting the Ram Air is not causing the hesitation or g on heavy acceleration as you initially hit the throttle. That sounds more like a fuel starvation issue. I am assuming you are using a carburetor, not EFI. If that is the case there are a few places you can look at. For some carbs there is a accelerator pump actuating arm that has two linkage holes in it. The outer hole is used if you are able to do so with no hesitation issues upon acceleration. If you fuel demands are higher than "normal" you can move the actuating rod to the inner hole to get faster actuating with more travel when the throttle is flipped open. Another possibility it the accelerator pump diaphragm or plunger (depends on carb type) is leaking (internally or externally). I have also seen where debris gets into the fuel bowl and ends up having crud bock the accelerator pump jets. If the float level is too low it can also cause a hesitation.

Anyway, I would look at that kind of stuff before trying o solve the issue with Ram Air behavior. FWIW, if you leave the vacuum motors unplugged the flaps will remain open all the time - but be sure to plug the vacuum hose ends at the vacuum motors so the intake manifold does not end up with a vacuum leak.. It is what I do, but I also do not drive in the rain <g>...

Awesome advice, the carburetor is an edelbrock electric choke that I know nothing about, I did close off the vacuum as you suggested, the snorkel is open. It's not much better, "pops" when I get down on it to pull into traffic, I'm getting now as it hesitates turning left, etc, I do not want it to stall and I get t boned! I have done a lot of the work on the car, but not the carburetor, so I need to read up, I'm on a budget, so I get it right! Thank you!

 

[mrgmhale]

Agree with mrgmhale, the stumbling/stalling issue is not because of the ram air being closed. Most probably, as stated by megmhale, it has something to do with the accelerator pump circuit in your carburetor, or with the timing being retarded, or maybe just a vacuum leak making the engine run lean. Post what carb you have and maybe we can help.

Another item worth checking is the distributor vacuum advance diaphragm. If it is ruptured or leaking it will cause a flat spot in low end performance, and cause a loss of fuel mileage. Here are some links I posted re: how to test those diaphragms, and how to check for ported vacuum getting to the diaphragm. I also go over the Thermal Vacuum Switch, which you likely have (or had), and how it functions as well as how to test it for proper operation at normal and cool temperatures. I know I go through a lot in these videos, but I also feel it is worth checking them out and checking your distributor vacuum advance system for proper vacuum line routing as well as for proper operation.

 

[mrgmhale]

Awesome advice, the carburetor is an edelbrock electric choke that I know nothing about, I did close off the vacuum as you suggested, the snorkel is open. It's not much better, "pops" when I get down on it to pull into traffic, I'm getting now as it hesitates turning left, etc, I do not want it to stall and I get t boned! I have done a lot of the work on the car, but not the carburetor, so I need to read up, I'm on a budget, so I get it right! Thank you!

Hesitation or bogging down on turns is indicative of a carb float level that is too low, either because the float level needs to be adjust, or because of fuel starvation (plugged/plugging fuel filter, kinked fuel line, cracked rubber fuel line on the "suction side" of the fuel line system where it is sucking in air into the fuel line, failing/leaking fuel pump, plugged fuel cap vent or plugged/misconnected fuel evaporative control system.

I do have, of course, some more YouTube video footage showing how to change the suction side (of the fuel pump) fuel lines, and the fuel pump (on a 302, but similar for Ford engines across the board). It may well be worth your while to take a look to see if there is anything you need to look at. Even on those older vehicles with carburetor based fuel systems there are so many things that can cause this kind of grief.









I hope the video help, especially with the kind of info you will not see in shop manuals...