Stock Carb Vacuum Lines Disconnect

[ARCHINSTL]

I am awaiting the return of the stock carb from National Carburetors - repaired under its warranty - dunno what was fixed yet, but I'm pretty sure at least the accelerator pump; it was supposed to check everything else, though.

In the meantime....As of this year, vehicles made prior to 1996 will no longer be subject to emissions testing in MO.
So...
When I reinstall the carb, I intend to hook up all of the vac lines and compare the driveability with what it was before. However - I would like to eliminate the "running on" aka "revs not dropping much between shifts." I have been through the Fed diagrams in the FSM many times, and am of course still confused. It seems to be related to the temp switch/"A" vac switch/vapor canister, based on the problem encountered of RPM cycling when the "A" switch is hooked up, and which disappeared when "A's" vac line is plugged - at least based on the FSM's chart of occurrences at certain RPM and temperature points. The "running on" appears when the "A" is plugged, but not when the line is hooked up - but then the RPM cycling returns.
So...
Who has experience in removing what vac lines and still have the thing run at least OK? I realize that most folks who have the Weber seem to have only the PCV and one line from either the gas filter or the TVSV hooked up solely to the bottom line of the distributor vac advance (the top two vac lines of the advance are plugged?) - and that's it for vac lines.
I would leave the HIC line hooked up to the snorkel flap, as that seems prudent for cold weather.
It seems that I can disconnect all of the other lines, whether to the vapor canister or the EGR or the EBCV or the "A" and "B" vac switches and it will run OK. My HAC valve is already disabled, as STL is not elevated enough to require it.
I am uncertain about the choke breaker and the choke opener, however - it seems that they are relevant only for reduced emissions, but I dunno. Ditto for the two fuel solenoids - leave connected or not? Leave the water temp sensor by the TVSV hooked up?
Should the TP be left hooked up? It would seem that the carb's AAP should stay hooked up to the TVSV.
Should all three of the vapor canister's top tubes be plugged or rerouted or ....?

I guess - who has done anything like this? What is the minimum of vac lines the stock Aisan carb needs?
Thanks to all.
Tom M.
PS: My primary goal is driveability and the secondary goal is economy. Power would be nice, but that is a "C" item here.

[keith]

You need the canister as is. If you plug those lines, your gas tank won't vent. Then about every ten miles your engine will die and you will have to go and remove the gas cap to break the vacuum in there.

You will need all the lines hooked up to your vacuum advance, but one of those switches in front actually shuts off the vacuum advance under certain circumstances. The EGR could be turned off and the engine would probably run better for it.

You will want to keep the idle up for the AC. The "running on" is a feature to keep the engine from dying when it drops to idle. It keeps it from dropping too far. Before I switched to the Weber, I never thought that was a problem, but it only occurred as the engine rpm was within a few hundred of idle. It didn't hang at high rpm.

[ARCHINSTL]

My AC is non-operative, so I unhooked the "B" switch vac line "T" to the AC VSV and the actuator. Are you implying that I need this hooked up?

My thought on the vapor canister was to unhook it from the carb and the VSV and leave the canister line originally to the carb unplugged - I stated it poorly.

I already have the lines to and from the HAC to the dist vac adv plugged - this seemed to make sense, given STL's altitude (the CA and Canadian versions do not have a HAC).
Tom M.

[takza]

I'd take a hint from Typhrus....

"I have all of my vacuum hoo-hah detached from the VSV and the TVSV, distributor aside. Whatever sources into the side of the carb is still there. Hoses are plugged and fitting capped where needed. Dist bypasses the HACV and utilizes the ported vacuum source above the 2ndary in the side of the air horn above the butterfly valves."

I'd leave the VSV/canister hooked up...so you might gain something from the gas tank vapors.

As far as the idle not dropping fast enough...There is a diaphram based gizmo that controls this? But I think if you don't have it working you might see stalling at stop signs? Might be able to adjust it to drop faster?

As far as the choke...you need all this connected...just keep the choke shaft lubed....or put in a manual choke?

I'd just carefully read the description for each gizmo to see what you gain or lose.

I expect to try this myself sometime...might see some mpg gain?

[keith]

OK, so you don't need the AC idle up, but you do want to keep the choke breaker and choke pull off. Engines run very poorly during the warm up period when these don't work.

[Typrus]

My AC idle-up is shot anyway. lol.
My VSV (the thing directly into the intake that sources vacuum for either the dist or the TVSV) is plugged to the TVSV and still feeds to the dist.
The canister plugs into one of those side ports as far as I can tell.

Whats funny is I'm no running my HACV, and I'm still fine. Lol. Though, that means I'd have to jump out and tweak the mixture for every thousand or so feet I go down in altitude. Above 5000 or so the HACV doesn't do anything more. Though, it'd still be good to tweak on the way up.

Just make sure the dizzy is hooked up right or it'll run horribly and like to die off-idle at stop-lights.

[ARCHINSTL]

Thanks for the responses thus far.
I had a suspicion about the TP being responsible for the RPMs not dropping immediately the clutch is disengaged - but what threw me is that with the "A" switch connected, the RPM drop was fine, but when it warmed up, the 2300-to-1800 RPM cycling commenced. The RPM drop was still fine, but the cycling occurred.
With the "A" vac line plugged, the cycling disappeared, but the RPMs did not drop.

After looking through the FSM, the closest I could come to the cycling situation was in the table for the Vapor Recovery system, wherein various things happened at the 2200 and 1900 RPM points and rise in temperature and admission of vapors to the carb and tank, which mirrored my situation with the cycling.
I could find nothing about the RPM drop situation specifically, however. Obviously, there is some relationship between the cycling elimination and the RPMs not dropping. And I had adjusted the TP a long time ago - guess I'll take another look at it when the carb is returned.

Have I explained this adequately? I'm having a problem with syntax today... I've noted that various folks have experienced cycling at idle +/- speeds, but no one has encountered my 2300/1800 situation. Ditto on the RPM non-drop.
Tom M.
EDIT - - I noticed in a post on another thread that keith mentioned that his old carb was cycling between 2400 and 1800; so, I am not alone...

[Petros]

I know this one, and I am still studying it. I will share what I know, taking each in turn. If you have no vacum leak and your linkage is adjusted properly, you can adjust how quickly the throttle returns to idle if you like.

But first, if the idle is high and hunts, it is likely a vacum leak somewhere, it should not do this if working normal. I had this exact problem several times when a larger vac hose came off or developed a leak, look for that first. The carb is not likely the cause unless it has an internal or gasket leak (not likely but possible). The emission control devices will not cause this either unless they are not working properly.

Do not disconnect the vapor canister. It does not affect drivablity, power or econmony, but may harm economy if not working properly. Test for proper function and vacume leaks then keep it in place. It also reduces emissions without effect on economy or drivablity, a good thing. The only way it woud cause a fast idle and rpm hunt is if there is a leak in the hoses.

If you can not adjust your idle down to 800 rpm (when it is warm) you likely have the linkage out of adjustment or have a vacum leak, you must first locate any leaks and fix them, and then adjust all of the various linkage devices (any could cause the throttle not to return to idle). I use carb cleaner spray to find vacum leaks (engine slows when it sucks in the carb spray).

IF no vacumn leak then check linkages. Check the throttle cable is not too tight (adjust at the mount), check that the choke idle speed adjust is not too high and backs off all the way once the choke is open, obviously check that the idle adjustment is backed off. Both of these adjustments are at the throttle shaft on the back side of the carb (side where the throttle linage is attached to the shaft). All of these adjusments are easy to do with the airfilter housing removed and the vacum line to the airfilter plugged. Use good lighting and you should be able to see how the linkage changes idle speed as it warms up. If the throttle plate does not come all the way down to the idle speed adjusting screw (on the back side of the throttle shaft/same side as cable) there is something out of adjustment. Try to locate which device on the throttle shaft/linage is holding it open if it will not return to idle after it is warmed up, and your choke is all the way open. If your choke does not open all the way it will also run crappy and keep it from returning to idle.

Once you know everthing is working properly, you have all the linkage adjusted and know you have no vacum leaks, then you can adjust the throttle dash pot. To improve the throttle responce when you back off the throttle you only need to adjust the throttle dash pot linkage. This is a little vac. diaphram on the front side of the carb (side opposite the throttle cable) with a linkage to the thottle shaft. It is designed to keep the throttle plate from slamming shut too quickly (which would make for a momentary rich mixture). If it is out of adjustment it will not return to idle fast enough between shifts. There is no reason to disconnect it since it should not affect economy or driveablity if adjusted correctly.

You have to locate the adjustment on the throttle shaft on the front of the carb. You can watch it's action on the front side of the carb at the throttle shaft when you advance and quickly releast the throttle. If you disconnect the vacum line to the dash pot diapham you will see how quickly the throttle returns to idle. You can either back-off the adjuster screw on the linkage so it never touches the throttle linkage, dissconnect the linkage, or simply disconnect the vacum line.

I suggest backing off the adjustment so it only just slows the return to idle at the end of its travel, this way it is still working, but less obviously. It should not interphere with your shifting, if it does you simply back off the adjuster screw so it only affects the last little bit of throttle movment.

You do not want to disconnect the vacume lines to the distributor. These advance the spark timing at part throttle (high manifold vacum) to improve part throttle economy (as in normal cruising speed). Then when you stomp the throttle open (as to pass or go up a hill) the timing backs off to prevent ping. There is an emission device, I think it is the little temp operated vacum valve on the thermostat housing, that disegages the vacum advance at certain engine temps to lower emssions. If you by-pass this device and have the vac advance connected directly to the manifold vacume it should improve the cruise economy and have no effect on driveablity. You also should check that the dist. vacum advance works or replace it. You shoud be able to use only one vac hose, the other is used to disable the vac advance (a little experimenting will determine which is which, but I think it is the one closest to the dist. side that you should cap off).

I think if the hot air riser on the aircleaner was disabled it would help both power and economy. You want to block the vacum to the diaphram that opens the flap to take hot air from the exhaust manifold heat riser, and make sure the flap is in the position to draw from the cold air side. Warm air reduces the comubstion peak pressures (warm air is less dense), drawing from the cold air side should improve both max power output and economy at part throttle.

I have not yet determined what to do with all of the other vac hoses yet. One device is for altituded compensation (makes it leaner as you go up in altitude), a good thing I think if it works as advertized. It is the device held in a clip on the right side of the carb above the EGR valve. There are other devices that adjust the fuel/air mixture under certain driving conditions, and I do not know how they affect economy/drivablity. Many of the vac lines power devices that have no effect on economy but do reduce emissions, I would keep these in place if they are otherwise in good working order. But I have not sorted them all out yet. I there are several that do effect economy, like the vac advance disconnect valve and the EGR and the carb air heat riser. Of course you want to block off any vacume leaks you create when you disconnect any vacume hoses.

I will keep you all updated on what I find next, the study continues as my time allows.

Good luck.

[takza]

I think if the hot air riser on the aircleaner was disabled it would help both power and economy. You want to block the vacum to the diaphram that opens the flap to take hot air from the exhaust manifold heat riser, and make sure the flap is in the position to draw from the cold air side. Warm air reduces the comubstion peak pressures (warm air is less dense), drawing from the cold air side should improve both max power output and economy at part throttle.

I tend to think the opposite. I've been running with a partial rad block and full hot air intake all winter at around 90F intake temps. Also ran hot air up to +156F in summer with a temp probe in the air cleaner. I don't notice a power loss...espec with advanced ignition. I've seen maybe a 7% mpg gain this winter vs last...but also have a Condensator going and new additives in the engine oil.

I use straight manifold vac on the air door and have a limiter screw in order to adjust it open some in the summer. If I do WOT...the door opens and the engine sees cool air.

One guy claimed a 15% gain in mpg using a hot air intake (different car)....most don't see this much if any.

The theory being that hot air is less dense so it causes less fuel to be used (O2 sees less Ox) and also helps to vaporize the fuel.

[Petros]

it is possible the carb needs warm air to fuction properly, but hot air intake in a normal running engine makes efficiency drop. Also in very cold climates you will get ice forming in the manifold unless you have heated air intake. The fuel vaporizing causes a drop in temp resulting in ice formation, not good for efficiency or driveablity.

At normal temps it is a fact of the theomdynamics of the engine that colder more dense air is more efficient. Same is true with fuel vaporization, if you got 100 percent vaporized fuel in the manifold you will lose both power and efficiency. You need an optimal mixture of vapor and tiny fuel droplets to get the best power and economy.

[takza]

Same is true with fuel vaporization, if you got 100 percent vaporized fuel in the manifold you will lose both power and efficiency. You need an optimal mixture of vapor and tiny fuel droplets to get the best power and economy.

Some people claim at least...to be able to get engines to run on pure vapor and to get high mpgs. Problem seems to be the way they refine gasoline these days...too much heavier stuff in it that clogs these systems up. Previously it wasn't "cracked" so much and was more of a straight run distillation process?

There seems to be the inventor/tinkerer version of reality and the reality subscribed to by those trained by/in industrial-educational sources...sponsored by auto related industry.

Not trying to start an argument...just mentioning what I've heard...I'm still on the fence.

I had an engine ice up one time...I was using a cold air intake and bypassing the hot air stove....happened on a day when the temp was around 32F and there was wet snow. Only happened that one time over 2 yrs or so.

[Petros]

I have heard these stories of 100mpg carbs on Cadalacs 35 years ago. In collage I tracked down every single one I could find, even found an expired patent for one. They are all myths. Either hoax, chranks or ignoramics passing around runors and non-sense. IT is impossible.

In collage I had access to engine labs where we tested every componet of the system. From the carb to the tires, and everything in between. I know, and the manufacturers know, excatly where every bit of fuel engergy is being spent in the engine. It is not mearly book learning, but actual hands-on testing that I have made this determination. The best theoretical economy you can get with a Prius sized car is about 90 mpg IF you can convert fuel 100 percent into mechanical energy (which we know is impossible).

You will not improve economy by increasing vaporization of the fuel in the system. This is a proven fact, tested on many engine dynometers. Most cars today already acheive 98 to99.8 percent combustion efficiency (meaning you can not get any more energy out of the fuel in the chamber). So what are you going to achieve by "better" fuel vaporization? Even if possible you would not even see the differance at the pump. There are other losses in the whole engine/car system and all the effort has been on changing that, to improve overall efficiency, but not combusition efficiency.

[ARCHINSTL]

BOYS - BOYS !
Do I have to put you in separate rooms?
Seriously, you guys have valid points. However, I intend to go with leaving the HAI hooked up, for cold starts. Back in the day, my Morris "A" series BMC motors had their own "HAI control" - the air cleaner had a snorkel that you rotated in Winter to the manifold for heated air - made a BIG difference (yeah, right-bless the Brit hearts).

So - when I get the carb back (it was misplaced down at National and it is doing 2nd day Air):
1. I will be hooking up everything, including the connected, but vac-unplugged, "A" switch and starting over.
2. I will leave the plugged HAC valve still plugged-if CA and Canadian cars don't need it, then at STL's altitude, neither do I (so there are 2 operating vac lines to the dist instead of the OE three).
3. I will leave the AC idle up disabled.
4. I will be installing new vac lines, even though the current ones are less than 2 years old and appear just fine -who knows ???
5. I will retorque the manifold nuts, even though...
6. I will recheck timing and adjust all.
7. I will return with a book report.

I guess there is a point that I missed when beginning this thread: I guess OUR carbs need some/most of the vac lines, because they were designed for them and for emissions control, whereas the Webers are designed for performance and not for emissions control, so they do not rely on vac anything - makes sense.
I would hazard that I was just seduced by the clean appearance of the Weber installations and thought that "Heck, if the Italians don't need spaghetti, then the Japanese don't need noodles."
Tom M.

[Typrus]

lol.
Whatever you say. I guess what I've seen with my own eyes means jack diddly shit.
Lemme guess. Its IMPOSSIBLE to get 23mpg with a Ford Excursion? Hah. Whatever you say.




Will not improve through increasing vaporization? Well, what if the factory system had below a desired proportion of vapor to droplet? Then, lemme guess, I'm an idiot.


I'm in a bad mood. You're more experienced than me. Theres exceptions to everything, even the laws of physics (ever heard of the Singularity?) and theres rules to everything. One of those is that you shouldn't vent your irritation in an intellectual discussion. I'll likely pay.



Find a way to increase the amount of heat you kick out the tailpipe. By that I mean increase the amount of heat that is kept in the combustion chamber versus leeching into the block. Ceramic coatings on pistons, combustion chambers, and the faces of valves? Cylinder sleeve of some exotic metal with a very low thermal transparency? That'd increase fuel economy, simply out of a drastic increase in thermal efficiency and thereby the amount of heat from any unit of fuel that is used for power. Most internal combustion engines are less than, what? 30% thermally efficient? Imagine if a 70 degree temperature rise can blow the top off of a milk jug what a several-hundred degree increase would do for increasing the volume of the combustion charge, thereby creating more downward force via more pressure. Same amount of fuel making more torque and horse. Thereby less fuel needed for the same jobs. Better efficiency. Did you all experiment with that?


There is a big difference between the real world and the world of what the book says. Things can behave VERY differently in real life than in the lab.

[takza]

I guess there is a point that I missed when beginning this thread: I guess OUR carbs need some/most of the vac lines, because they were designed for them and for emissions control, whereas the Webers are designed for performance and not for emissions control, so they do not rely on vac anything - makes sense.

I USED to think that way, but I suspect that Typhruses carb guy knows better. I think he might have just reduced the jet size in the carb (maybe) and disconnected all the extraneous crapola...resulting in a Japanese made Weber.

Now if Typhrus...our good buddy....would do us the honor of drawing out a detailed vac line map of his setup...ARCHINSTL would then go ahead and try this...whereapon takza...assuming that this does work out OK...will do the same thing to his carb.

Or am I dreaming?