Is this MPG in line with my trucks package

[boreguard]

New to the board so I hope I ask my question and provide the right info for a concise answer.
My truck is described as follows:
1979 1/2 ton 2 wd 305 auto.
I got the truck recently and changed the timing gears while changing the front oil seal. It needed a tune up; changed plugs, wires, dist cap & rotor. Replaced carb. w/ a rebuilt one from Autozone. The stock intake manifold had been replaced with and Edelbrock (not really sure why because nothing else seems to be performance or aftermarket) and the carb is the regular Q-jet type (4 BBL)and style.
Truck is timed and running well cranks at the slightest touch of the key.

I put the second tank of gas in her today and the fuel consumption show's to be 10.9 MPG !
MAN THIS HURST MY FEELINGS.
I expected better, but maybe this is in line with this drivetrain, it doesn't feel like it's geared real high, but I've no idea what the rear end ratio is.
Is this in line and about as good as it should get, or am I missing something ?[/font]
Many thanks
Dennis Neal

[VileZambonie]

Welcome aboard. Now that would be low fuel mileage. What trans do you have? We need to know your final drive ratio also. Try advancing the timing a little and does it smell like it's running too rich?

[boreguard]

Thanks for the welcome Vile. It's a T350 not sure the rear end ration just yet, will try to determine that this afternoon after church. However like I said it doesn't feel as though it's geared real low, but I guess unless I've a tach on it I wouldn't be able to even determine whether or not that's high.

As to timing I am worried I've got it too advanced cause I get a slight ping when accelrating while crusing at 50 ish MPH or above, it doesn't last long. As to running rich...yes it does hint at it but not real overpowering. I'd accepted it as about normal since most of the Smog stuff is non functional.

Is it normal to have the vaccuum advance have vaccuum on it all the time ? I thought that the vaccum didn't occur until acceleration, but going by the vaccum line routing sticker I've got it where it's supposed to be...I think.

Oh yea, single exhaust and original aircleaner if that were to be of question.
Many thanks again for the welcome.
Dennis Neal

[boreguard]

It looks like my axle ratio is as follows; (HC2) 2.76 (G87)8.5 Ring gear.
Looks like I got some carb or carb & timing issue's that dosen't quite seem obvious yet "gettin my gas"
Thanks for any input,
Dennis

[Fordeatinz71]

haha, you have the exact same truck i use to have.  i had a 1979 Chevy C10 Custom Deluxe SWB with a 305/4-bbl, Th350 and a 2.76 rear end.  had factory A/C and that was about it...truck sure did run good though and it got more than 10 mpg...mine was around 15 or so...

my '83 Sierra K1500 with 305 and 2.73 rear end running out of OD got 13.6 with the A/C blowing cold and averaging 75-80 on the freeway...and it's a 4x4, just to give you a hint of what you should be getting...

[VileZambonie]

Well I would suggest first doing a tune up and setting the timing. Use a good top engine cleaner to decarbonize it and then change your oil. Your timing may be retarded due to a pinging issue related to a heavily carboned up 305 (yes I've seen this 90874589798475687498576984 times) I think that's a good starting point for you. How long have you had the truck?

[boreguard]

Extensive tune up already completed, plugs, wires, cap, rotor, including timing chain and gear. And brand new rebuilt carb.

Hadn't had the truck but about a month.

Doesn't appear to have any vaccum leaks, set timing to factory spec. Doesn't tear the black top up, but does run okay. I'm suspect of the carb and settings.
Dennis

[boreguard]

Thanks FORDEATINZ71 that's what memory and past experience told me that I should be getting.
DN

[VileZambonie]

Do you know what your ignition timing is set at now?

[boreguard]

I set it at what the book recomended...I think it was 8 deg. btdc.

I was using a dwell/tach to check carb adjustment, not sure I can get it any closer to being about right. But I noticed that when I rev it up, hold the high rpm's, and etc. that the butterfly's for the secondaries never open, shouldn't they ?
DN

[Fordeatinz71]

the best way to set your carb/timing is with a vacuum gauge.  that will get you as close as you can get and can diagnose other issues. 

http://www.centuryperformance.com/vacuum.asp <---click here


as for your secondaries...yes, they should open blipping the throttle in neutral.  i had this same issue...instead of posting everything again, read over this...this basically tells you everything to look for and what fixed my problem...
carb secondary issue

[boreguard]

I couldn't get the link on the "carb secondary issue" to work. Thanks for the other one.
DN

[boreguard]

In an effort to narrow down my poor gas mileage culprit I've discovered that I dont have the check (maybe called delay valve) between the vacuum source and the dist. Is this necessary ? I noticed doing a search that there was a pic posted in effort to answer another person's question and it showed the "valve" I'm referring to in between the dist and vacuum source.
(305 CID w/auto, Q-jet, in a 79 1/2 P.U.)

Thanks
Dennis

[Captkaos]

There shouldn't be a valve between the source and the distributor.  What gas mileage issues are you having?  I merged the topics back together and didn't edit my post...

[ccz145a]

That is a low mileage value. You should be getting at least 15.

Does the truck run well, not sluggish?

How are you measuring mileage? If using your truck's odometer, then are you sure it is correct?

Have you timed yourself between mile-markers at a steady speed of 60mph. This should be 60sec, and your odometer should have recorded 1 mile.

Your secondaries could be opening too soon, they are vacuum operated and can be tightened to open late. Take your breather off, look at the secondary butterflys as give the throttle a good goose for a couple of seconds, the secondaries should open delayed about a second. They should not be instantaneous, that would be too loose.

Just throwing stuff out there that I would check.