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73-87 Chevy _ GMC Trucks => Performance => Topic started by: muddnutz on February 17, 2009, 08:36:01 pm

Title: fuel efficieny questions/issues
Post by: muddnutz on February 17, 2009, 08:36:01 pm
  I have a stock 305 with dual flows, stock exaust manifold,edelbrock intake and carb(1407?) lucky to be getting 10 mpgs wich really sucks on a 16 gallon tank and family lives 180 miles away. what can I do to improve  it.   my truck is a 86 k-10 no lift on 31's stock gears
Title: Re: fuel efficieny questions/issues
Post by: choptop on February 17, 2009, 10:35:39 pm
Check your rear gears. It should be ok with 3:73's. but it could have higher gears which wouldlug the engine. Other than that, it may be a tune up issue
Title: Re: fuel efficieny questions/issues
Post by: 82Shortbed on February 17, 2009, 10:44:03 pm
1407 seems like too much carb for a 305, its a 750 manual choke.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 18, 2009, 05:38:11 am
may have no. wrong it is a 600 electric choke ..new plugs ,wires, cap and rotor-timing marks are hard to read on balancer  ??? also 700r4 tranny  whatever the factory gears are in a stock plain jane k-10.they have never been changed i got thee truck from my dad he bought it new in Oct 85...also no emissions on it anymore
Title: Re: fuel efficieny questions/issues
Post by: VileZambonie on February 18, 2009, 10:24:46 am
check your carb # to be certain of what it is.
Title: Re: fuel efficieny questions/issues
Post by: eventhorizon66 on February 18, 2009, 11:10:50 am
Well you need to know your ignition timing.  Even if it's where it should be, you can usually advance it a few degrees without consequence to improve efficiency.  The find the TDC mark (groove) on your balancer, clean it, and paint it (steal some of your GF's/Wife's white nail polish).  That will make it clear as day.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 19, 2009, 02:15:14 pm
  CARB IS A 1406---600CFM ELECTRIC CHOKE  ILL HAVE TO BORROW NEIGHBORS TIMING LITE TONITE.  DOES IT NEED TO BE ON THE LINE OR OFF TO THE LEFT OR RIGHT? NO BEFORE OR AFTER MRKS JUST A LINE ON THE DAMPER--NO TAB ON TIMING COVER
Title: Re: fuel efficieny questions/issues
Post by: VileZambonie on February 19, 2009, 05:20:28 pm
how can you time it using a timing light without a pointer?
Title: Re: fuel efficieny questions/issues
Post by: enaberif on February 19, 2009, 06:53:19 pm
how can you time it using a timing light without a pointer?

With skills!

Or perhaps he overlooked it as I did!
Title: Re: fuel efficieny questions/issues
Post by: eventhorizon66 on February 19, 2009, 07:01:27 pm
I bet he did.

Look straight down behind the water pump.  It should be at the 12 'o clock position on the dampner.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 19, 2009, 07:47:20 pm
 i see the pointer  what I'm asking is should it be dead on with the mark or a few deg btdc or aft? you cant tell on the pointer just a few jagged edges which line is which
Title: Re: fuel efficieny questions/issues
Post by: rockable on February 19, 2009, 07:53:02 pm
'86 should be 4 degrees BTDC with the vacuum disonnected from the distributor and plugged.  That truck should get 15 city/20 hwy thereabouts, if it's tuned and carbed correctly.  You've got a lot of room for improvement, assuming the long block is up to snuff.

As I recall, each "tooth" on the marker is 2 degrees.  TDC is to the right.  You really need to clean it off, so that you can read it.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 19, 2009, 09:50:39 pm
  it is a rebuilt 305 haven't checked comp or sure on mileage since dist is also aftermarket pos box fried a while ago.. don't mean to sound like such a dumbarse but timing pointer isn't marked which is tdc, it has several points and a tube beside it? does this make any sense my camera died or i would take a pic
Title: Re: fuel efficieny questions/issues
Post by: Jims86tpisub on February 19, 2009, 11:19:33 pm
If its an 86, I wonder if it came with the computer controlled q-jet....If he changed the carb., that may be his problem....no tps to tell the computer what throttle position the carb is at.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 20, 2009, 05:44:32 am
 no more comp. or comp controlled dist.
Title: Re: fuel efficieny questions/issues
Post by: VileZambonie on February 20, 2009, 06:50:44 am
(http://i6.photobucket.com/albums/y228/Sabaka454/timing.gif)


Now your carb is also an issue. If it's right out of the box it will be calibrated rich. Get a calibration kit, jet it down a little. If you don't have access to an analyzer it will be trial and error and reading plugs.
Title: Re: fuel efficieny questions/issues
Post by: Jims86tpisub on February 20, 2009, 12:08:13 pm
could he possibly use the edelbrock afr meter, with the o2 sensor......unless he has changed the manifolds, he should still have a bung for the sensor.
Title: Re: fuel efficieny questions/issues
Post by: muddnutz on February 20, 2009, 05:35:48 pm
  appreciate all the help im going to re-check the timing in the a.m. ;D