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Help With MPG
https://www.slantsix.org/forum/viewtopic.php?t=45882		 Page 1 of 2
Author:  Two Lane [ Sun Aug 07, 2011 9:11 pm ]
Post subject:  Help With MPG
What have you done that has helped you to get more miles per gallon out of your slant/6?

(71 Duster 225/904 40-thousand actual miles. P/S. Pertronix II, MSD-6, HEI coil, 2.5" exhaust, new old stock factory carb, 2.94 gear)

A/C off, flat interstate, no wind, 65 m.p.h. = "maybe" 16-18 max. avg.

May as well build a 318/340 2-barrel dual exhaust motor if it's improbable to do much better than this. :(

Would love to drive the car everyday, but the MPG just dollars ya to death.

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Any suggestions? What MPG would you expect to see as-is? What avg. MPG are you getting?

Thanks for your help in keeping some hope alive for more MPG!!

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ADDED NOTE:
If you're pleased with *any* particular choice of ignition system, that's wonderful! :) Everyone should certainly be free to make their own choices, per their own preferences, for their own reasons.
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THREAD TOPIC: MPG
Author:  DusterIdiot [ Sun Aug 07, 2011 9:22 pm ]
Post subject:  Timing...
What is your advance without the vacc. pod connected, at your highway RPM?

What is your total advance with the vacc. pod plugged in?

That's probably part of the equation...for MPG, getting about 48 degrees of advance at highway speed/rpm...you probably are fairly short at that point.

-D.Idiot
Author:  USAJon [ Sun Aug 07, 2011 10:55 pm ]
Post subject: 
taller then stock rear tires
Author:  Rick Covalt [ Mon Aug 08, 2011 2:46 am ]
Post subject:  Mileage
Just as a reference. I ran my 85 truck (Shaped like a brick) to the Elk creek race. and It was loaded with everything but the kitchen sink.Parts, tools, food,tent...etc. And I got 18.7 MPG running down there, and about 18 running home. Drove 65 down and 70-75 home. Truck has an automatic and 2 barrel. No real tuning done either. Should be able to get 20MPG with it pretty easy though.

Rick
Author:  SlantSixDan [ Mon Aug 08, 2011 7:14 am ]
Post subject: 
You should definitely be getting better mileage than that. Do some additional work on the fuel system as advised over at FABO. Make sure to do a good, careful valve adjustment. Note the factory base timing spec of 0° (TDC) tends to give poor mileage. One question: Pertronix and MSD? How is that? The Pertronix setup is self-contained.
Author:  Ross [ Mon Aug 08, 2011 9:28 am ]
Post subject: 
I just checked mine again. With a 4spd manual with 1:1 4th and 3.55 rear gear I got 18.6 mpg driving 70mph on the highway at 3k rpm and a little backroad driving, that's also with a lead foot. If I drove like a grandpa I could probably squeeze 21 out of it.

Cody
Author:  supton [ Mon Aug 08, 2011 9:37 am ]
Post subject: 
Stock tire diameter? A larger tire would make the car seem to go less far than what it does, giving the impression that the mpg is suffering. Can you verify odometer versus GPS or mile markers, using 10 or more miles?
Author:  raPoM [ Mon Aug 08, 2011 10:04 am ]
Post subject: 
Quote:
Stock tire diameter? A larger tire would make the car seem to go less far than what it does, giving the impression that the mpg is suffering. Can you verify odometer versus GPS or mile markers, using 10 or more miles?
Agreed. Also a 2.94 gear is the perfect in town/highway gear for a slant with the stock/near stock tire size IMO.What is our tire size? You should be seeing 22-26 mpg pretty easily with that car/gear/mods at 65 mph. I am with Dan on this too,how do you run an MSD and Pertronix?Thats like running two tires on one wheel.
Author:  Doc [ Mon Aug 08, 2011 10:28 am ]
Post subject: 
Quote:
...new old stock factory carb...
Holley or Carter BBS?

Either way... check your valve lash & timing curve... adjust "as needed".
Then lean-out the carb's jetting.
20-22 mpg should be easy to get if the engine has decent compression.
DD
Author:  USAJon [ Mon Aug 08, 2011 10:32 am ]
Post subject: 
Quote:
Quote:
Stock tire diameter? A larger tire would make the car seem to go less far than what it does, giving the impression that the mpg is suffering. Can you verify odometer versus GPS or mile markers, using 10 or more miles?
Agreed. Also a 2.94 gear is the perfect in town/highway gear for a slant with the stock/near stock tire size IMO.What is our tire size? You should be seeing 22-26 mpg pretty easily with that car/gear/mods at 65 mph. I am with Dan on this too,how do you run an MSD and Pertronix?Thats like running two tires on one wheel.
a taller tire dia keeps the RMPs lower @ cruse..Ive done it on all my six drivers
Author:  raPoM [ Mon Aug 08, 2011 12:23 pm ]
Post subject: 
Quote:
Quote:
Quote:
Stock tire diameter? A larger tire would make the car seem to go less far than what it does, giving the impression that the mpg is suffering. Can you verify odometer versus GPS or mile markers, using 10 or more miles?
Agreed. Also a 2.94 gear is the perfect in town/highway gear for a slant with the stock/near stock tire size IMO.What is our tire size? You should be seeing 22-26 mpg pretty easily with that car/gear/mods at 65 mph. I am with Dan on this too,how do you run an MSD and Pertronix?Thats like running two tires on one wheel.
a taller tire dia keeps the RMPs lower @ cruse..Ive done it on all my six drivers
While that is true,it doesnt always help mpg. Just because you cruise at a lower rpm,does not mean it will be optimal for economy,for the best economy you want to cruise in the power band.
Author:  Two Lane [ Tue Aug 09, 2011 8:43 am ]
Post subject: 
Thanks for all the helpful replies, fellows! :)

This is a "chemo x 3 week", so it'll be a few days before I can get the info to answer the Qs raised.

By gosh, there may be hope for the lil' Duster yet! :)


Thank you for the generosity & knowledge on the Slant Six forum!
Author:  Two Lane [ Tue Aug 09, 2011 9:06 am ]
Post subject: 
The MSD-6 box adds multi-strike, i.e. multi-spark to the Ignitor II.

They have a complementary and synergistic effect...both work better when used together.

You would not need a MSD-box with the newer Ignitor III, as it includes built-in multi-spark, but no Ignitor III module is offered for the slant/6,
only the Ignitor II.

Pertronix offers their own multi-spark Second Strike box for use with the Ignitor and Ignitor II, but it's more costly than an MSD-6.


HTH :)
Author:  SlantSixDan [ Tue Aug 09, 2011 9:10 am ]
Post subject: 
No, it doesn't really help me understand. Could be because I've not found MSD's stuff to be particularly dependable; I've always had better results at much lower cost with the HEI upgrade. Also, I've never before heard of any "synergistic effect" from combining MSD + Pertronix. That doesn't necessarily mean it isn't so, but…where does that idea come from?

…and is it possible this "synergistic" ignition setup might not be working as well for you as you think it is?

…and is it all based around the stock '71 distributor?
Author:  Two Lane [ Tue Aug 09, 2011 9:30 am ]
Post subject: 
Scroll down this page for instructions on:

"How To Mount 2 Tires On One Wheel"

http://www.pertronix.com/support/tips/default.aspx#a6


HTH :)
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