Author Topic: Early Chevy 305 Gas Mileage??  (Read 11950 times)

Offline choptop

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Re: Early Chevy 305 Gas Mileage??
« Reply #30 on: April 29, 2010, 08:32:25 PM »
Personally, Id hunt for a 350. It has more power on demand, no physical difference exterior wise, and can be made to perform better with simple upgrades. That being said, my 86 extended cab gets about 19-20 hwy with the 305 /700r4 combo unless its windy. then it get down to about 15. Keep in mind its a 2wd tho. I really am not sure what mileage I get out of my 85 k10 with the 350 because due to rear axle issues, I havent had a chance to really find out. I would definately ditch the 2 barrel when possible and upgrade to a 4 barrel, with a rv cam. This will help you both on and off the trail. The 6 is a better trail engine in my opinion because they are notorious for low end torque. Yes the 305 has more, but it will be at a higher engine speed, and may result in more wheel spin than beneficial.
  As far as the cold air induction, for years I drove Oldyellers 81 C20 with 350/400/4:11s with the air cleaner lid flipped. It was what everyone was doing for supposedly more horsepower. The I had an old man tell me to put it back on right, and hook the tube back up. With just that, I went from 9 mpg to about 11mpg. It seemed to run better too. Later, he rebuilt the carb for me and I got almost 15mpg. I was very happy, plus it ran like a striped ape. If I can get close to 15 with a 6000 lb 3/4 ton truck, your jeep should be fairly simple to get there. Main thing is a properly tuned engine, with a properly setup drivetrain. On your Jeep with 31's, I wouoldnt go more that 3:73s and that jsut because it seems the next upgrade is always larger tires. That engine with 3:73 should turn 33s pretty easy and not hurt your mileage too bad. Most economy is ruined because the final drive ration puts the engine in a lug condition under normal driving situatuons.
76 C10 Choptop,76 C10 Swb
85 C10, 85 K10, 85 K20,86 C10,86 K10 (all extended cabs)
86 C30 extended crewcab

Offline VileZambonie

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Re: Early Chevy 305 Gas Mileage??
« Reply #31 on: April 29, 2010, 08:44:54 PM »
How's the body on this jeep? Is it worth putting the time and money into? A friend of mine just did a TBI 350 with a 700R4 and he loves it. But if it were me I'd do a TBI 4.0L Jeep and Aisin Warner Trans with a 242 tcase.
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1974 GMC

Offline cherrycj7

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Re: Early Chevy 305 Gas Mileage??
« Reply #32 on: April 29, 2010, 09:19:11 PM »
The body is pretty good. The frame is the main thing I am holding onto.It is extremely clean. So, yes, it is worth it. I just want a V-8, haha. The 4.0 is a great engine and all, but the  "cool" factor just isnt there in my eyes. Its in almost all of the cherokees and wranglers from 1990-2000 somethin. I want this jeep to be something that people look at and are impressed about, gets decent gas mileage and is good off road. I think with a V-8 i could accomlish these thngs. Its a classic (1979) so i am going to take it to car shows too.

Offline 1980c10

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Re: Early Chevy 305 Gas Mileage??
« Reply #33 on: April 29, 2010, 10:06:25 PM »
a 305 will give you reasonable mileage for a regular driver. I would definatley go with the quadrajet.  Then tune it perfectly and you should be able to see 15 mpg. My 82 lwb c10 had a 305 w/ a quadrajet, 4wd, 4 speed manual trans no od, 31x 10.5 15 bfg's would get me 18 no matter where or how i drove. The engine never missed a beat and ran like new. I had it tuned and vacuum lines routed some what differant from stock and timing set by a guy who is known for tuning these stock engines and carb. best of luck. btw he recomended stock air cleaner housing.

Offline cherrycj7

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Re: Early Chevy 305 Gas Mileage??
« Reply #34 on: May 01, 2010, 01:37:46 PM »
1980c10, Thanks for your responce. You have been one of the only positive ones reguarding the 305. I am guessing that the 18 is highway? What it get city? thanks

Offline Stewart G Griffin

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Re: Early Chevy 305 Gas Mileage??
« Reply #35 on: May 02, 2010, 11:12:57 PM »
In the meantime, this article should give you some hope.  Their tires are close to yours too:

(may need to scroll down)

http://forum.73-87chevytrucks.com/smforum/index.php?topic=14391.15

Offline jaredts

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Re: Early Chevy 305 Gas Mileage??
« Reply #36 on: May 03, 2010, 06:31:16 AM »
I said nothing bad about the 305.  I think your biggest hurdles to economy are in order:  The TH400 tranny and carbureted fuel delivery.  A TBI 305 with 700R4 transmission should yield you over 20mpg's easily.  The TH400 is a great choice for serious off roading, but economy is not its strong suit.  TBI compared to a carburetor will yield a couple of mpg's, a 700R4 compared to a TH400 will yield????  My guess is 4 to 5 extra mpg.'s.

Offline 1980c10

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Re: Early Chevy 305 Gas Mileage??
« Reply #37 on: May 14, 2010, 12:53:47 AM »
I would always get 17.5 to 18 mpg city or highway, maybe because It didn't have an OD. If power is your priority I would go with a 350 ci. If mpg and budget are of more concern I would go with the 305 ci. You will be able to find a 305 much cheaper than a 350 due to demand. an overdrive trans would also be worth the extra money spent for sure.

Offline Stewart G Griffin

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Re: Early Chevy 305 Gas Mileage??
« Reply #38 on: October 07, 2010, 05:01:45 PM »
Last 3 fillups:

15.14 mpg

16.72 mpg

16.10 mpg.

 


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