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Re: Dumb question about improving gas mileage
Reed #295628 May 28th 2009 5:13 pm
Joined: Aug 2005
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N
Supreme Master
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N
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Wow Reed..why don't you come out here and dial my 85 in? lol


Nate Breece
Re: Dumb question about improving gas mileage
NateB #295633 May 28th 2009 5:32 pm
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Heh.


Windows- they're what make a van worth owning!
Re: Dumb question about improving gas mileage
Reed #295716 May 28th 2009 11:50 pm
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Posts: 1,317
old hand
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My mileage has worsened since developing exhaust leaks from every possible point that can leak before the cat, I assume it's affecting the O2 sensor readings. 9MPG city, 13-14 highway with a 3.9 but I'm not fixing any of them since I'm working on a 318, but if you have exhaust leaks try fixing them.


In search of the illusive prairie lobster
"If you dont stand behind our troops feel free to stand in front of them"
Re: Dumb question about improving gas mileage
vervepipes #295741 May 29th 2009 2:40 am
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Verve- Actually, I say fix the leaks AND replace the cats- most likely they are clogged and/or have failed internally causing excessive backpressure. Universal fit high-flow catalytic converters are reasonably priced these days. If you can afford it, go with 2 1/4 inch line all the way back and get some free flowing mufflers too.

I have heard the late 80s/early 90s Mopar TBI systems are terrible as well. You might actually do better mileage-wise with a carb.


Windows- they're what make a van worth owning!
Re: Dumb question about improving gas mileage
Reed #295792 May 29th 2009 11:43 am
Joined: Apr 2009
Posts: 29
newbie
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Reed, I don't have a 318 or 360, but a 400 big block, any changes to your advice? Thanks.


- Pete
vanlivin.com
Re: Dumb question about improving gas mileage
peterparker523 #295807 May 29th 2009 12:23 pm
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Wow, that makes it worse. Okay, what that really changes is my tranny recommendation. No automatic four speed with overdrive was ever offered for the big bloxk, so you are stuck with your stock 727. But you can still tweak it like i said- remove the accumulator spring, back out the line pressure screw.

I still recommend a Offy Dual-Port or Edelbrock SP2P intake, but for a carb I would say get a thermoquad or get an Edelbrock performer, 500 CFM with the electric choke. I would recommend the dual port over the SP2P however. You might still be able to get away with using the Holley 4360 carb, but it flows 450 CFM and is a spread bore carc. That might be too little air flow for a 400, but if you are building for low RPM torque it might do just fine.



Windows- they're what make a van worth owning!
Re: Dumb question about improving gas mileage
Reed #295843 May 29th 2009 3:02 pm
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Also, swapping to an "RV" cam or a cam designed for low RPM torque and HP would help.


Windows- they're what make a van worth owning!
Re: Dumb question about improving gas mileage
NateB #295855 May 29th 2009 4:02 pm
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G
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now this question is for super beast. Just like putting a taller tire on the rear wouldn't that increase your gas mileage tremendously by itself? I mean then you would always be running downhill!


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Re: Dumb question about improving gas mileage
G_ROLLER #295955 May 29th 2009 10:41 pm
Joined: Oct 2007
Posts: 1,317
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Is the a518 not an over drive version of the 727?


In search of the illusive prairie lobster
"If you dont stand behind our troops feel free to stand in front of them"
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