SuperNova76

Whats the average gas mileage for a 305 v8 smallblock?

There is something VERY wrong with my nova, Its only getting....Dare i even say it....4-5 mpg, and thats AFTER getting it adjusted from running to rich.

Any thoughts?

MrPbody

A bunch of things are out of wack. That's deplorable fuel consumption.

Check cam and ignition timing. Is it a 2-bbl. or 4-bbl.? What is the rear axle ratio? Stock engine, or modified for performance? Please gve as much detail as possible.

Jim

SuperNova76

1976 Chevy Nova Sedan
250,000 Miles ( estamated, the speedo only goes till 99,999)

305 SB V8
THM350 auto tranny
2 barrel carb
Everything is original, no performance parts, However parts have been replaced, as they do wear out but everything was OEM.

Not sure what that gear ratio is, I would go out and find out but I do live in the Not so great northwest and its been pretty wet out and i dont have a garage.

I have noticed it smells heavily of gas, but the air/ fuel mixture is correct, also there is this one random tube hanging off of the left side of the carb and its not attached to anything...It doesnt leak or anything like that.

The previous owner noted the car only got about 8-10 mpg at best.

The timing is a little off, it does grumble when I shut it off, sometimes more than other times.

gatoratoy227

between 8-13 mpgs

__________________
NO! ,we can't stop here, this is bat country. Raoul Duke

Scrapper

those were prety good moters in the pontiac. my dad loved his and they do have quite abit get up and go his had a 4bcarb and not bad gas milage.

MrPbody

Pontiac? Huh?

The "heavy smell of gas" is a key piece of information. How are you determining the air/fuel ratio is "good"? Was it "sniffed" on a scope or exhaust gas analyzer? Simpy setting the idle misture screws won't make it "right".

The gas smell could come from the charcoal canister being saturated, but that doesn't usually cause bad mileage. If the carb is flooding or leaking, THAT will. If the fuel pump is leaking, that too, will cause it. Smell your oil to see if there's fuel in it.

Keep the details coming...

Jim

bobss396

With the right rear, you should be getting at least 16 out of it. Get your fuel system sorted out, look for a bad section of steel fuel line and make sure that your rubber connections are good as well.

Bob

SuperNova76

Sorry For the absence, I have been very busy with two jobs.

Now that i have a few weeks before I get busy again i decided to get back to work on the nova!

So after a long sit, I had the carb completely rebuilt.....HOWEVER! After reinstalling I try to start it and after a few seconds of running i smelled gas very heavily and turned it off and looked and there was gas all over the intake manifold....WHY?

I have everything tightened up real good and everything is connected..I also notived the new seals were completely soaked in gas (paper cardboard stuff) on the carb.

j cAT

being a 1976 I not sure its been a long time ...did you check out your fuel cannister and the controlling valves...these valves have diaprhams...if they split it can cause low mileage and gas leakages..in the engine compartment..

the problem on starting the rebuilt carb may be the fuel line/gaskets...these parts have to be handled carefully and the gaskets replaced...

bobss396

Sounds like a hung up float. You can try rapping on top of the carb with a screwdriver handle a few times, but the float might not be hung right inside. Did the carb have a guarantee with it?

SuperNova76

Well After further inspection I discovered that while i watched it run, gas was spilling over the top of the carb and all down the sides and onto the engine, The guy who rebuilt my carb told me when he fixed it the diaphram had been destroyed,probably caused by back firing up through it, so i am guessing this is the case again....no there wasnt a guarantee or anything like that.