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25 MPG with a 408 ??? Yup!! #500582
10/18/09 09:29 PM
10/18/09 09:29 PM
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New Mexico
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dmerc Offline OP
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After a little fooling with timing and carb low speed circuit I got 25 MPG with my Duster. It can be done guys!! Next thing is to get to the track. I expect it to run 14.5's at 5000 ft which will be equivalent to 13.5's at sea level. Car has never run better and I'm just at 30 total timing with 15 degrees of vacuum advance added on.

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500583
10/18/09 09:46 PM
10/18/09 09:46 PM
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Posts: 480
Kentucky, USA
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derekeh Offline
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Kentucky, USA
Dang. Id be happy if I could get my 70 cuda with a 340 to get even 15 mpg city :/

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500584
10/18/09 09:50 PM
10/18/09 09:50 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Circle Track
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Lincoln Nebraska
Quote:

I got 25 MPG with my Duster.


repost your specs. I want some.


live every 24 hour block of time like it's your last day on earth
Re: 25 MPG with a 408 ??? Yup!! [Re: RapidRobert] #500585
10/18/09 09:55 PM
10/18/09 09:55 PM
Joined: Oct 2007
Posts: 3,857
Oregon
hooziewhatsit Offline
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Oregon
Quote:

Quote:

I got 25 MPG with my Duster.


repost your specs. I want some.






So throw that same set up in my W200, with the aerodynamics of a brick, I wonder what it would get


If you ever find yourself in a fair fight, your tactics suck.
Re: 25 MPG with a 408 ??? Yup!! [Re: hooziewhatsit] #500586
10/18/09 10:14 PM
10/18/09 10:14 PM
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Posts: 1,061
New Mexico
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dmerc Offline OP
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New Mexico
Here's the recipe:
Magnum heads with tight quench .030. Bowls opened up. Stock valve job.
Wiesco dished pistons
Mopar Performance M1 Dual plane intake
Roller cam Compcams #20-000-9 506 lift 216 intake 224 exhaust duration.
Mopar orange box. 340 HP manifolds with a TTI 2 1/2 inch exhaust system.
Distributor that I recurved for timing all in at 2000 RPM.
This is a big one: Thermoquad 850 carb. Best carb I've tried and I've tried them all.
700R4 Chevy trany with converter lockup. But any overdrive trans would work.
3.23 8 3/4 rear end
Aluminum radiator with electric fans. Fans don't operate at anything over 40 MPH so you gain at least 1 MPG with that mod.

Last edited by dmerc; 10/18/09 10:34 PM.
Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500587
10/18/09 10:22 PM
10/18/09 10:22 PM
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo Offline
Too Many Posts
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Manitoba, Canada
What speed are you driving at to get that mpg? With that rear gear and overdrive, you must be keeping the rpm very low...

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500588
10/18/09 10:25 PM
10/18/09 10:25 PM
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Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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What is your (measured) CR and what gas?


live every 24 hour block of time like it's your last day on earth
Re: 25 MPG with a 408 ??? Yup!! [Re: DaytonaTurbo] #500589
10/18/09 10:26 PM
10/18/09 10:26 PM
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New Mexico
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dmerc Offline OP
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Running 65 to 70 MPH. At 70 I'm turning about 1800 RPM. I'm running a 28 inch tire too. 275/60 -15

Re: 25 MPG with a 408 ??? Yup!! [Re: RapidRobert] #500590
10/18/09 10:32 PM
10/18/09 10:32 PM
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New Mexico
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dmerc Offline OP
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Calculated CR is 10.5 to one. Dynamic effective compression is 8.5 to one. Cranking pressure was 155 PSI. I always run 87 octane but on this last gas mileage run I put in 91 octane. I really don't know if it made any difference.

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500591
10/18/09 10:34 PM
10/18/09 10:34 PM
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Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Thanks bro


live every 24 hour block of time like it's your last day on earth
Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500592
10/18/09 10:38 PM
10/18/09 10:38 PM
Joined: Aug 2005
Posts: 5,994
Salem
Grizzly Offline
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Posts: 5,994
Salem
You did it!

I'm going to be optimistic and say you will hit somewhere between 12.8 and 13.2 seconds in the quarter.

Now let's see.... Skinny tires, lower it, and 3.08's; sounds like 27mpg to me?


Mo' Farts

Moderated by "tbagger".
Re: 25 MPG with a 408 ??? Yup!! [Re: Grizzly] #500593
10/18/09 10:41 PM
10/18/09 10:41 PM
Joined: Dec 2004
Posts: 1,061
New Mexico
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dmerc Offline OP
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New Mexico
If I gear any taller I'll be able to feel the individual power pulses on the highway! LOL!!

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500594
10/18/09 11:29 PM
10/18/09 11:29 PM
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IL, Aurora
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ademon Offline
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IL, Aurora
Is this your everyday driver

Re: 25 MPG with a 408 ??? Yup!! [Re: ademon] #500595
10/19/09 07:06 AM
10/19/09 07:06 AM
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Posts: 1,061
New Mexico
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dmerc Offline OP
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It's an every day driver. Now I have to complete the project. The body (except for engine bay) is ugly and the interior is shot. It's kind of a sleeper except for the big tires. Dog dish hub caps. Nothing fancy.

Re: 25 MPG with a 408 ??? Yup!! [Re: dmerc] #500596
10/19/09 08:10 AM
10/19/09 08:10 AM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
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Brookeville, Md
why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.


[IMG]http://i66.tinypic.com/pui5j.jpg[/IMG]
Coming soon!!!!
Re: 25 MPG with a 408 ??? Yup!! [Re: Mr.Yuck] #500597
10/21/09 08:11 PM
10/21/09 08:11 PM
Joined: Mar 2005
Posts: 1,545
Seattle, WA
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375inStroke Offline
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Seattle, WA
Quote:

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.




13.0 MPG?

Re: 25 MPG with a 408 ??? Yup!! [Re: 375inStroke] #500598
10/21/09 08:51 PM
10/21/09 08:51 PM
Joined: Feb 2009
Posts: 982
W. Sacto CA. USA
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phantomx Offline
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I'd be interested in the MPH when you run it. Sounds like a good street combo.
Travis..


70 GTX project, orig 440-4, 4 spd, track pack, FC7, stripper/street racer special.
Re: 25 MPG with a 408 ??? Yup!! [Re: phantomx] #500599
10/21/09 09:01 PM
10/21/09 09:01 PM
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Posts: 9,982
Ansonia, CT
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CJK440 Offline
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Ansonia, CT
I'm assuming this was mostly, if not all highway??


2017 Contusion Blue Challenger T/A 392 M6 "BLKNBLU"
Re: 25 MPG with a 408 ??? Yup!! [Re: phantomx] #500600
10/21/09 09:07 PM
10/21/09 09:07 PM
Joined: Dec 2004
Posts: 1,061
New Mexico
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dmerc Offline OP
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Quote:

I'd be interested in the MPH when you run it. Sounds like a good street combo.
Travis..




I'll be taking the Duster to the drags to see what it will do on Sat. I'll report back. Hope I don't blow it up!!

Re: 25 MPG with a 408 ??? Yup!! [Re: CJK440] #500601
10/21/09 09:17 PM
10/21/09 09:17 PM
Joined: Dec 2004
Posts: 1,061
New Mexico
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dmerc Offline OP
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Quote:

I'm assuming this was mostly, if not all highway??




All highway except for a little drag race with a mustang on the freeway. (guess who won?)

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