MPG increase and better performance (maybe?)

[Anonymous]

I was thinking (very dangerous for me). I've been having a small problem with vacuum as some of you may have noticed. I finally figured out the vacuum modulator valve was bad on the tranny which caused poor idle while driving. Well, that's been fixed. But as I was repairing that problem I happen to notice something that I never noticed before.

When I replumbed all the vacuum lines I forgot to plug one of the ports on my intake manifold that was not being used. More air was being sucked into the "log" because of this mistake (daaahhh!). Yet, after adjusting the idle and fuel mixture, I noticed that the car ran MUCH smoother. It also seems to get better gas mileage and better performance with the vacuum nipple uncapped.

Am I missing something here? Or did Ford have some type of filter on the nipple instead of having it capped? For those of you who don't remember, I have a block and head from 1977.

Any suggestions or ideas?

Chris

 

[CobraSix]

To me that means that you may be running your carb too rich.

You should have no vacuum leaks.

If you run too rich...the addition of un metered air will help lean out the mixture to the proper ratio (I.E...runs better). Since it runs better and probably has better power, you let off the gas more and get more mileage. That is my hypothesis.

Slade

 

[CobraSix]

when I mean rich...I mean jetted riched...not the idle air adjustment.

Slade

 

[Anonymous]

Slade, you could be right, it could be the jet or I may even have too much fuel pressure being feed to the carb. via the electric fuel pump.

There's also something else I have noticed. My fuel mixture screw can be tighten completely and it doesn't make a difference.

BUT when I uncap the vacuum nipple on the intake manifold, I CAN adjust the mixture screw with no problem. This is what's troubling me the most.

Sure wish I could get ahold of a manual that shows a properly plumbed '77 200. I noticed (Mustang manual) in the early 70's Ford ran a vacuum line from the intake manifold to the breather on the I-6's. Must be part of the closed emissions solutions (Ford's).

 

[rbohm]

8) i agree with slade, it sounds like your motor is running too fat. probably a combination of things, high float level, high fuel pressure, and an internal leak.

 

[JT81stang]

The line that runs from the intake to the breather wasn't part of the closed emissions, it ran to a temp. valve that controlled the flap in the breather snorkle. When cold the flap closed and the engine took in warm air from the stove pipe, and as the engine warmed up the flap would open and it would take in the cooler air. That flap needed vacuum to make it work.

By having a vacuum nipple uncapped, the motor can use more air and that why many of the guys on this forum have changed to bigger carbs.
more cfm.

John

 

[Anonymous]

So far I'm starting to think it's more than one thing.

rbohm, I think you and slade are right on it. When I bought the car a few months ago that was one of the first things I noticed. I really didn't have the ability to adjust the carb. too much. It seems like the only think that I can adjust it the fast idle screw. Shouldn't I have three adjustments. I have only the mixture and fast idle adjustments on the carb. (it's a Carter reman.)?

I did have a vacuum problem but that was solved. More and more I think about it most of my problems I'm having is with the carb. And if it is running fat than that would also explain the unusual amount of white smoke puffing from the exhaust lately (maybe, it doesn't smell like burning oil).

This leads me to another question...should I use ported or unported vacuum setup (early 70's 250's setup...I think).

 

[CobraSix]

White smoke I think is unrelated. White smoke (after the car is warmed up) is usually from a leak in the head gasket. Running rich will give you blackish smoke. burning oil will give a blueish/blackish smoke.

The fact that you can't adjust the idle screw is interesting. I had the same problem this morning actually. My problem was that my choke assembly is not working right and the choke plate was not opening up properly, causing my car to run really rich (and really poorly). Check and make sure your fast idle (choke) is not jammed. Make sure it is working properly. That may be a problem...

Slade

 

[61Futura]

With only a small float to turn off the fuel, I would imagine that too much fuel pressure from an electric pump would fill the bowl higher or maybe even start to overflow it. Maybe you need a fuel pressure regulator that you can set for whatever the stock pump pressure is.

Compare the new pumps rating to stock. My 170 should have 3.5-5.5 psi at 500 rpm. My book doesn't mention how high it gets at higher rpm's

I'd like to find the glass bowl cover for my Holly so I could always see the fuel level in the bowl when I tuning things up under the hood.

Steve

 

[rbohm]

8) on some carbs the idle speed and the fast idle are adjusted with the same screw so when you set one right the other follows.

 

[Anonymous]

With only a small float to turn off the fuel, I would imagine that too much fuel pressure from an electric pump would fill the bowl higher or maybe even start to overflow it. Maybe you need a fuel pressure regulator that you can set for whatever the stock pump pressure is.

Compare the new pumps rating to stock. My 170 should have 3.5-5.5 psi at 500 rpm. My book doesn't mention how high it gets at higher rpm's

I'd like to find the glass bowl cover for my Holly so I could always see the fuel level in the bowl when I tuning things up under the hood.

Steve

I waven't thought about the fuel pressure until lately. But ya...that makes sense. This could also be part of the reason why I run fat alot. Cool.

 

[Anonymous]

Stang200

What carb do you have? Is it the Autolite 1bbl? My old carb did exactly the same thing. Put the idle mixture in all the way and the car would run better. I never could get it running right.

Get yourself a good rebuild kit and a gallon of pro carb cleaner from NAPA (not that stuff that comes in the can)

Take the thing apart, give it a good overnight soaking in the carb cleaner then blow out the passageways with compressed air.

Rebuilding those carbs isn't that hard - just make sure everything is out of the carb before soaking it -- that stuff is caustic.

Put it back together with all the stock specs and I bet you'll be running a lot better.

 

[Anonymous]

Thanks for the input. It's a Carter YF rebuild from Autozone. When I bought the car a few months ago it had been setting for more than a few years. The owner drove it once in awhile but not often. It probably needs a GOOD cleanly like you suggested.

I'm also seriously considering removing the electric fuel pump. I don't know the reasoning behind it's installation but the machanical pump was left in place. I think it's (carb.) is getting too much fuel pressure and the mechanical pump is leaking Again. I don't know if the electrical pump was put in because of the leak or some other reason.

Ahhhh the joys of restoring an auto

-Chris