Indexing Spark Plugs

To my understanding you want the gap to face the intake valve, exposing all of the spark to the mixture, but upon further research, some engines like them indexed AWAY.. 

You'd need an engine dyno to get your optimal positioning.  You can make a mark on the plug body and one on the head to determine when it's where you need it to be, and use washers (they make them just for this purpose) to get where you need to be.

Also , it's only apparently good for 1-2% at best, so unless you're racing for money, you may want to save the $500-$1000 of dyno time needed to get optimal plug indexing and put it towards porting the heads or better induction/exhaust..  (or a roller cam, or nitrous)

Jim

11-12 mpg where and under what usage?  I got 13-14 on the highway with a warm 460 and 3.00 gears..  Check the carb and all vacuum lines, check the timing, check the air filter, and exhaust.  A nice free flowing dual exhaust and a fresh and tuned carb go a long way towards economy, as does an easy throttle foot.  

When is the last time it had a thorough tune up?  Get a set of fersh plugs, gap them and run it down the highway, pull into a rest area and check one.  Also check one after running around town.  Advance the timing a bit and see what that gets you as well. 

I got 4 mpg on the highway with the 545 and 4.33 gears, so it could always be worse..

:-)

Jim

I get about 8mpg now I guess, the 3.56 gears really helped....  Tough to get mid 11's normally aspirated on pump 93 at 4000+ pounds and not drink fuel I guess

What weight Mobil 1 oil?  What cam?  Have you tried just being extra gentle on the throttle? (I get 5 extra MPG out of my Daily driver if I try hard enough)

What does it smell like?  If you follow someone while they drive it, does it ever smoke?

I'm not too good at MPG trick as I just drove mine less when it got too expensive..  Do you always check the air pressure in your tires and keep them at the high end of the range?  Stop and go traffic will kill mileage in a 4200+ pound car for sure.

Unless your 2bbl is tuned a bit rich somewhere and it covers up by being lean elsewhere I'm running out of ideas. 

I could give you 100 ideas on how to make it faster, and 50 to make it more efficient, but they all start to cost more than a few extra fill ups.  Like rollerizing the C6, using lighter synthetic fluid in the rear, headers, TBI, different heads, etc..

I'll keep posting so this stays at the top, you can alos try the 335 series message board over on Network54, they might be able to help somewhat as well..

Jim

That still seems low for a 400  2v combo..   Maybe try a trip where you dont vary the speed much and see if you get into the middle teens?  I know they weren't rated much higher than 14 or 15 new, so you're close.  Maybe try looking around for a set of the closed chamber 2v heads (Aussie).  You might find more efficiency with those heads and at not too high of a cost.  As for the cam, maybe there is a better design that could gain you some MPG?  Lots of places to look..

Jim