Re: Trying for gas mileage but still want a V8
[Re: gch]
#493156
10/10/09 04:38 PM
10/10/09 04:38 PM
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Joined: Sep 2004
Posts: 6,906 IL, Aurora
ademon
master
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master
Joined: Sep 2004
Posts: 6,906
IL, Aurora
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when will you get a return on your money buy removing the 360 and installing a rebuilt 273 to gain maybe 5 mpg? i would remove the 4bbl on the 360 and install a 2bbl set up first and see what happens you can probably find someone that will give it to you for free, next thing i would look at is your timing to make sure your running full vacuum advance in the area of 50 deg total at light cruse, make sure you have a clutch fan, my 4.7 03 dakota only gets about 19 mpg highway with the 5 speed auto turning 1,800 rpm at about 60mph. are you sure the barracuda got that milage was the gear stock? tires stock, speedo working right? Not tring to be negative, but i would try to maximize what i have before i undertake all the work and $$$$
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Re: Trying for gas mileage but still want a V8
[Re: stumpy]
#493163
10/10/09 07:46 PM
10/10/09 07:46 PM
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Joined: Jan 2007
Posts: 774 Midland,Tx
wyldebill
super stock
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super stock
Joined: Jan 2007
Posts: 774
Midland,Tx
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i bought an aspen from a guy in colorado who had build a late 70's crew cab. it had a 500 inch motor. the build was designed to make as much torque as possible. he was telling me that he would get around 18mpg on the hwy. torque is the key. your combo with the tall tire and tall gear will eat you up. the slant motor makes more torque than the 273 will.
Last edited by wyldebill; 10/10/09 07:48 PM.
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Re: Trying for gas mileage but still want a V8
[Re: wyldebill]
#493164
10/10/09 08:18 PM
10/10/09 08:18 PM
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Joined: Jan 2003
Posts: 9,982 Ansonia, CT
CJK440
master
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master
Joined: Jan 2003
Posts: 9,982
Ansonia, CT
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Put a thermoquad on the 360 along with a wide band A/F meter ($200 for an innovate LC1 with digital gauge) and tune ignition and carb for mileage.
2017 Contusion Blue Challenger T/A 392 M6 "BLKNBLU"
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Re: Trying for gas mileage but still want a V8
[Re: stumpy]
#493165
10/10/09 08:35 PM
10/10/09 08:35 PM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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don't bother with a 273. pistons are too expensive to get high compression/0 deck. copy hotroddave's 318 build...
the key to mileage is high compression and little overlap. you'll get neither with a stock bottom end 273 and that cam.
or another option is his short block (KB167 pistons at 0 deck), magnum heads, lunati voodoo 60400. the magnum heads will make significantly more power than the 273 or '302 heads.
or use an '85 up 318 (roller cam motor, 302 heads or magnum heads) with the KB167's, and get the roller cam reground by bullet cams, probably with the HRL256A lobe on the intake and exhaust if using magnums, the HR259/316 on the exhaust if using the 302's...if you're maximizing MPG, use the HR247/306 lobe--similar adv. duration as a stock cam, but about 10 more .050 dur than a stock LA 318 cam, and a lot more lift (almost as much lobe lift as a stock cam's valve lift!) use that lobe for intake and exhaust and you'll have 23 degrees overlap on the stock 112 LSA
my combo is a stock '86 short block, pistons .055 in the hole, magnum heads home ported by me, magnum roller lifters, pushrods, and stock mag rockers, thin head gaskets (9:1 comp measured) RPM air gap, headers, eddie 600, and the roller reground by bullet with the HR259/316 lobe for both intake and exhaust.
on the butt dyno, engine has as much power as my old XE262 equipped 360, but I'm getting 3mpg better (18 vs. 15) in my 3900 lb 5th ave. the great thing with roller cams is the aggressive profiles...my cam has 10 degrees less .050 duration than the old XE262, but only 3 degrees less duration at .2", and more gross lobe lift. area under the lift curve is the same or better than the old cam, but with 13 degrees less overlap.
Last edited by patrick; 10/10/09 08:50 PM.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: Trying for gas mileage but still want a V8
[Re: patrick]
#493166
10/10/09 09:03 PM
10/10/09 09:03 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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I predict worse mileage with the 273. A small motor trying to push a big lump equals poor mileage.
You'd be better off buying the LM1 someone mentioned and tuning your current 360. 360's can get good mileage, but not with an off the shelf carb, especially a Holley generic type carb.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Trying for gas mileage but still want a V8
[Re: Supercuda]
#493168
10/10/09 09:31 PM
10/10/09 09:31 PM
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Joined: Jan 2003
Posts: 4,323 NY NY
340duster340
master
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master
Joined: Jan 2003
Posts: 4,323
NY NY
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these hyper-mileage 273 threads turn up every now and again, but there is never a follow up thread, because building a 273 for mpg does not make sense.
honestly, you drive a truck its only going to get so good with a vintage powertrain under the hood.
1966 Dart GT
...down to only 1 mopar for the first time in 15 years!
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