350 and 10.5MPG

[Elpresidente]

Recently I put in a GM performance crate 350, on top of that I put an Edelbrock performer intake and 650cfm carb.
I can't tell the exact timing, as my timing mark does not line up even close with the tab mounted on the engine. Engine runs smooth and performs well, but there is lots of black soot in the tailpipe and the exhaust does smell like gas. It has an open air filter, haven't checked the plugs but will later today. Not sure of vaccum advance or carb tuning, I don't know how to do it properly so I didn't touch it (engine was setup by a friend just so it would run well, but we expected better MPG) . Engine now has 4000 miles on it and still gets 10.5MPG, and this is with 3.08 gears and a 700R4 O/D. Where should I start and what should I do?

[jaredts]

What's the condition of the carb., was it new?  What about distributor, is it the old one?  Black soot in the tailpipe, may not mean anything, but do you see black smoke coming out of the tailpipe?  Runs smooth at idle?  Choke hooked up and working correctly?  Timing mark doesn't line up?  Do you have the correct timing tab?  If you do your balancer may have spun and needs replaced.  Do you have a timing light?

[Elpresidente]

Carb is brand new, distributor is the old one from my 305 I previously had in there. Tailpipe smoke is a bit grey, mostly white though. it does run smooth at idle and the choke works fine, the timing tab I used came with the engine and is for an 8" balancer (which I have on there) I also have a timing light, thats how I found out my timing mark was off.
A stock 350 should be getting about 14 MPG if not better, correct?

[jaredts]

If its a two wheel drive you should be able to get 14 or a little better, but not much.  If there's some city driving in there 10.5 may be about right.  How did your timing light tell you that your timing mark was way off?  Does it show you are currently extremely advanced or retarded?  It sounds like the first thing you should do is bring your #1 cylinder to top dead center and compare that to your mark.  I would want to know what's up with that.  As far as it smelling like gas, that can be anything that could be wrong.  Did you put a new distributor cap and rotor on?

[Shawn0331]

I'm getting anywhere from 11-12MPG city with my '87. Lifted on 33x12.5's.

[bake74]

     I am with jaredts, first thing I would do is figure out what is wrong with the timing marks on your dampener.  Timing alone can do all kinds of funny things and make you get terrible MPG.  Guessing that it runs smooth and knowing it is running smooth is 2 different things.  Did your friend use any vacuum or RPM gauges when setting the timing and RPM ?  Or was it by the old "it sounds good and has great responsiveness ?"
     I personally would figure out the timing issue, then next would be tuning Carb. if it was me.

[Jason S]

It sounds like you have the wrong balancer for the timing tab your using.  8" balancers could have the timing mark 2 degrees before the crank keyway or 10 degrees before the crank keyway. 

[VileZambonie]

Jaredts has you going down the right path. follow his lead.

The carb is a brand new what? You said 650, 650 what? How is it calibrated? You took the distributor from your 305 but that still doesn't tell us what it is and how you have it set up. Not being able to baseline your ignition timing is an issue if you're trying to dial in your performance. Fix the basics then move on to advancing your performance and economy.

[Elpresidente]

Carb is an Edelbrock performer. and my mistake, its a 500cfm.

[str8bloc]

carbs to small i run a 600 on mine

[jaredts]

500 cfm is a little small, but that should just limit performance at higher rpm's, not the symptoms described.

[Donut]

What kind of rpm @ cruise?
Which crate 350 is it?

Jaredts has you going down the right path. follow his lead.

The carb is a brand new what? You said 650, 650 what? How is it calibrated? You took the distributor from your 305 but that still doesn't tell us what it is and how you have it set up. Not being able to baseline your ignition timing is an issue if you're trying to dial in your performance. Fix the basics then move on to advancing your performance and economy.

[VileZambonie]

So you have a 1403 or a 1404? You didn't respond to the other questions which doesn't give us much to go on to help you any further.

[Elpresidente]

Donut: Not sure, I dont have a tach in the truck. my guess is about 2000 @ 60MPH. its the GM goodwrench crate 350 from Jegs, part # 10067353.

Vilezambonie: carb # 1403. Anything else I didnt answer because I'm not sure about it.

I'm going to start by getting a proper balancer, figuring out what distributor I have, etc. because I found that  I do have the wrong balancer for the engine on there. From there I'm going to work at it with a buddy, he's knowledgeable with this as well. I'll update as things come along, and get more details. Thanks to anyone who has given advice so far.