350 getting 10mpg

[vince311]

I bought my 82 swb back in may....and I'm getting 10mpg consistently (with a light foot). Its got a 350 with headers, no smog, dual exhaust, edlebrock mainfold and edlebrock 650 cfm carb. I have no idea of the engine origin or how it was built (cam, internals, etc.) 

The engine has pep, but not a race engine by any means. Wondering what factors are contributing to my horrible mpg?

Would downgrading the carb to a 2-bbl help? I'm a novice at engine work...but able to learn. thanks for any pointers.

[Stewart G Griffin]

What type air cleaner you got?   Stock or open element?


No, i don't think switching to a 2 barrel would help, unless it's a weber, but that's another can of worms.

i turn a 16.8 in the quarter and get 16-17mpg.  And that's with a 2.56 rear.

[vince311]

What type air cleaner you got?   Stock or open element?


No, i don't think switching to a 2 barrel would help, unless it's a weber, but that's another can of worms.

i turn a 16.8 in the quarter and get 16-17mpg.  And that's with a 2.56 rear.

Hi Stewart,
I've got an open element for the air cleaner.

[Captkaos]

hmmm, Does it have a choppy idle or fairly smooth?
Where is the timing set?
If you have access to a Vacuum gauge, what is the reading on it?
Have you checked the plugs?
Is it running rich?
what kind of manifold?

[vince311]

hmmm, Does it have a choppy idle or fairly smooth?
Where is the timing set?
If you have access to a Vacuum gauge, what is the reading on it?
Have you checked the plugs?
Is it running rich?
what kind of manifold?

- idle is smooth.
- have not checked timing (I assume I will need a gun for that)
- do not have a vacuum gauge...
- have not checked plugs in a while (this i can do)
- Not sure if its running rich. Is there an easy way to determine?
- Manifold is an Edelbrock Performer

[Captkaos]

Yes would would need a timing light.
You should be able to get a vacuum gauge from any auto store.
Does the exhaust smell like gas.

[vince311]

Yes would would need a timing light.
You should be able to get a vacuum gauge from any auto store.
Does the exhaust smell like gas.

yes, the exhaust does have a gas smell to it

[Stewart G Griffin]

We should probably concentrate on the carb first;  What model edlebrock is it?

As pertaining to the air filter set-up, i feel that the stock air cleaner assembly will get you the best mpg.  This goes against what we've always thought, heard, read on the internet and conventional wisdom.  But i've been doing some research and it appears that the stock set up is designed to provide the engine with specific temperature air which is probably warmer than we might think.  This is what the hockey puck thing on the snorkel is for. Warmer air = leaner mixture which = better mpg.  Cooler air= denser mixture= more power at the expense of mpg.  Or something like that.

i will try to post a picture.  This is including the heat pipe.

But we should probably concentrate on the carb set up first.

[Captkaos]

If you have gas smell in the exhaust, you are running rich.

[vince311]

changed out my air filter and plugs for good measure. the plugs had normal wear....but changed them out anyways.

i noted that my tail pipes have quite a bit of dark soot in them. Is this another indicator that I'm running rich?

Update: I advanced timing a bit, and overall seems to run better. Tweaked the adjustment screws on the carb as well.

Going to see if this helps.

[Captkaos]

Get a vacuum gauge and hook it to the carb and adjust it for the highest vacuum reading.
Set the timing at around 8-10 degrees with the advance disconnected.