Horrible gas mileage

[78 Chevyrado]

You can't go by the guage as said above, you have to compare mileage to how much fuel it takes to fill it up. for example, I have a 20 gallon tank and when I get to E on the guage I still have 6 gallons left. Also when full it goes past the F on the guage but it only takes 4 gallons to get to the 3/4 full mark.



The point of having a dual spring is that when the spring you have fails eventually, the truck will be floored possibly causing an accident until you get a new spring. with dual springs when one breaks, the throttle will still go back closed and you can get it home.

[enaberif]

Originally Posted by 78 Chevyrado

The point of having a dual spring is that when the spring you have fails eventually, the truck will be floored possibly causing an accident until you get a new spring. with dual springs when one breaks, the throttle will still go back closed and you can get it home.

Makes sense.

Tho looking at pictures am I the only one thinking this motor has had some work done to it?

That isn't a stock intake manifold nor are those stock heads.

[Rain City]

The black hose you pointed out connects to this strange metal cone shaped thing...





The intake is a Edelbrock Air Gap Intake manifold (If that helps?) not sure the specifics of the holley carb...

[enaberif]

That weird can is the vac advance which allows for adjustment of timing for better mileage at part throttle.

Try to find some numbers on that carb and write them down.

I'm talking about the big fat one not the little skinny one. The one just to the right of your distributor in the first pic on this page.

[Rain City]

OK so I guess I am a little unclear...

So the right PCV valve will be according to my engine, or to the model carb?

And if I don't have one, then where does it go and what is there now?

I'm a dummy.

[enaberif]

Where does the hose in the picture go to?

[Rain City]

Goes here...

[Adams74Chevy]

Originally Posted by Rain City

Goes here...

That's the vacuum line for the power brakes booster.

[enaberif]

Ok so that is going to the brake booster.

Now you need to track down the numbers on that carb so you can find out what one it is exactly so you can find out where all the vac sources and what they do are located.

You need to make sure where that line is hooked to the carb is for the brake booster or for something else. If it is for the brake booster I do not know what that small can is.

But to hook up a pcv valve properly you may need to put a "T" into that line to run another line to the pcv valve which would go where the breather is in the left valve cover.

[impalamark]

I'm concerned about the "RANDOM HOSE " you referred to
it could be a transmission cooler that was abandoned
look for a small cooling coil [radiator like device wired or strapped
to the radiator} if that's what it is it would have had two hoses like that coming out of it. if both are disconnected it's ok to leave as is
these lines again should run toward the front of the truck toward the radiator
if it comes from the rear of the truck along the frame rail it could be part of the fuel system/emissions system or even a dual tank set up . find out where
and let us know .DO NOT just cut it out as previously suggested
MArk

[gchemist]

Ditch the aftermarket springs. Yea, the throttle will be hard to push with two springs. Locate some factory style springs. The are lighter and coiled together.
Original GM parts are available at http://www.montemania.com/genuinegmp...under_hood.htm

You can move it closer to use dual aftermarket springs. http://www.rjays.com/Lokar/lokar_images/SRK-4000-lg.jpg

You can use dual springs on the other side. http://www.mustangsplus.com/images/13213demo.jpg

Another option: http://www.hspnnews.com/images/uploads/QFT_spring.jpg

[powerdriver 1958]

The random hose is for a 3 line fuel pump(return line) Don't sweat it just plug it.You do need the PCV(Positive crankcase ventilation) valve.too much crankcase pressure will start leaks and just makes a mess.pcv valve can be in either valve cover just needs a 3/8 vac hose to manifold vacuum.look for a plug behind the carb in the manifold.parts store will have fittings to screw in the manifold to and hook a hose to.put the pcv in place of one of the breathers.More than likely the rubber grommet that secures the breather will be too large for the pcv and you will have to find one to fit correctly

[enaberif]

Originally Posted by powerdriver 1958

The random hose is for a 3 line fuel pump(return line) Don't sweat it just plug it.You do need the PCV(Positive crankcase ventilation) valve.too much crankcase pressure will start leaks and just makes a mess.pcv valve can be in either valve cover just needs a 3/8 vac hose to manifold vacuum.look for a plug behind the carb in the manifold.parts store will have fittings to screw in the manifold to and hook a hose to.put the pcv in place of one of the breathers.More than likely the rubber grommet that secures the breather will be too large for the pcv and you will have to find one to fit correctly

If you look under the air cleaner the manifold port seems to be on the #8 runner.

But its why I wanted him to find out the model of his carb. I know with the old qudrajets they had a spot for a PCV valve so I was thinking maybe that one the brake booster is using it for that... but its hard to say.

[powerdriver 1958]

usually the port his power brake vac is on I use for the PCV valve and the port in back of the carb for power brakes just to keep the hoses short and justs looks better.

[powerdriver 1958]

now for the mileage.Is this cammed up?rough idling cam can be for performance and be hard on mileage,the Vacuum Advance Chamber you have asked about in your picture could cause it.Have you noticed black smoke on acceleration?carb can be over fueling.With a Holley carb there is a part called the Power valve that can cause poor mileage.most Holley's have external adjustable floats and could be set a little high. have you checked the engine timing? Sorry about so many questions but there are quite a few things that affect fuel mileage.

[enaberif]

I'd assume since the truck looks like it has different, heads, intake and carb that this motor has had some work done to it and I can't see someone putting that much effort into this truck and not put a new cam.

[Rain City]

Yes it does have cams... the PO wrote down what kind they were (would have to find it) but I remember he wrote (for torque).

I will take a look at the carb tomorrow... unfortunatly I have to work - today I got sucked in to the truck time-abyss haha- know what I mean??

[enaberif]

Originally Posted by Rain City

Yes it does have cams... the PO wrote down what kind they were (would have to find it) but I remember he wrote (for torque).

I will take a look at the carb tomorrow... unfortunatly I have to work - today I got sucked in to the truck time-abyss haha- know what I mean??

Between the truck having a aftermarket cam, carb, manifold and heads.. I personally don't think mileage will there for you.

But the carb numbers will help.

[Damien]

The PVC valve can go in either valve cover. Everyone says the right side because that is where they are stock. The PVC helps remove combustion gasses (blow by) that have pushed the piston rings and will contaminate the oil and shorten engine life.
Assuming your truck has a 16 gal tank and you fuel gauge and Speedo are correct, which they probably are not. You would be getting about 6 mpg. If the miles are mostly in town, the numbers are not that far off (IN MY OPINON) of what they should be by looking at your engine set up.

You still have not said if the miles are city or high way and we do not know what the gearing of the rear end is.

Mythbusters tested a newer trucks designed with the help of a wind tunnel. Our trucks were not designed in a wind tunnel. I think they would have had different results if they tested a vehicle with the aerodynamics of a refrigerator.

[Rain City]

Originally Posted by enaberif

Between the truck having a aftermarket cam, carb, manifold and heads.. I personally don't think mileage will there for you.

But the carb numbers will help.

Will the PCV Valve even help my gas mileage?

The miles were highway...

I think I will do what someone had suggested and get an ACTUAL mpg by fillling the tank and running it till its empty.

[88 Dippy]

the unknown hose looks like it whent to the long gone charcole canister for the EVAP system

[Rain City]

OK so I'm pretty sure this is the carb...

http://www.holley.com/types/Street%2...raditional.asp

The only real number was this



thoughts?

[enaberif]

Pull the air cleaner spacer off and look at the front of it behind where the air cleaner spacer was.. should be numbers there.

[Rain City]

Here she is...


Looks like 1850-5, 1564

Changed my spark plugs today BTW... man that was not very fun.

[enaberif]

According to holley its a 600cfm carb but I don't know what the 1564 means.

Doing a search on google.. most people say those 1850s are junk so I'm not sure.

And yes where that large hose is coming from it the Brake Booster/PCV connector.

So go pickup a pcv valve for your truck, a "T" for the line, some extra hose and hook it up.