6 mpg... please help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bitchin85 · 01-13-2010, 08:22 PM

I got a long bed 2wd with a 355 with 305 heads, edelbrock streetmaster intake, edelbrock 500 carb, basicaly stock cam, stock distributor, mallory coil, automatic th350. Its got a 2.73 rear end and 31x10.5s... I know its no honda but I drive a lot and I think I should be gettin a little better milage. Also its real sluggish. Anyone have an idea of what It could be? Thanks guys

cableguy0 · 01-13-2010, 08:26 PM

the gears and that big tire are killing you. thats why its sluggish. you need to change gears. at least a 3.42 gear with that tire. its a mismatched combo from what you posted.

3r!c84 · 01-13-2010, 08:26 PM

how much compression with the 305 heads

bitchin85 · 01-13-2010, 08:29 PM

Ya I lknow it don't help. I had 275 55s on it and I was gettin about7 and I need a new rear end anyways so that's the next thing I'm gettin for it

bitchin85 · 01-13-2010, 09:11 PM

Not sure about compression ratio but its gotta be up there

Benelli · 01-13-2010, 11:32 PM

I'm feeling timing. yeah, the gears suck but I'd check timing, airfilters, plugs and wires, and maybe your driving? I'm not really sure.

qu1cks1lver56 · 01-14-2010, 02:08 AM

yeah check the timing, mine was off by 2 degrees and since i set it to where it needs to be it's freed up the motor and seems like the mileage has improved.
also make sure your tires are aired up to 35-40ish up front and 30-35ish out back (depending on what the tires recommend)
and if you were local to me i'd trade you my 3.42's for your 2.73's

Matt Man · 01-14-2010, 03:31 AM

put all synthetic fluids in your truck 3:73 rears, od trans new plugs wires check timing, tire pressure and most importantly check your hammer down foot.

gchemist · 01-14-2010, 05:09 AM

Tune it up!!

http://www.centuryperformance.com/tu...e-spg-148.html

http://www.tuningmadeeasy.com/tuning...e-wonder-tool/

bitchin85 · 01-14-2010, 07:14 AM

The plugs wires coil cap rotor are like a month old so that's all good. And an OD trans juat aint gonna happen for a while. I usually drive it normal or baby it but sometimes I lay into it.. How hard is it to swap out the gesars or do I have to find a new rear end

68 TT · 01-14-2010, 09:53 AM

Quote:

Originally Posted by *****in85

The plugs wires coil cap rotor are like a month old so that's all good. And an OD trans juat aint gonna happen for a while. I usually drive it normal or baby it but sometimes I lay into it.. How hard is it to swap out the gesars or do I have to find a new rear end

If you are on a budget getting a whole different rear end may be the least expensive route for you.

You could buy just the gears and carrier from the wrecking yard and do the rest yourself if you are mechanically inclined but it will take a couple hours to complete and won't save you much money. Plus if you get the tolerances wrong setting it up the gears will be noisy or wear out quickly.

bitchin85 · 01-14-2010, 10:04 AM

Ok I'm going to call around later for a rear end. Is a rear end with 3.42 or 3.73 hard to find?

68 TT · 01-14-2010, 12:34 PM

Quote:

Originally Posted by *****in85

Ok I'm going to call around later for a rear end. Is a rear end with 3.42 or 3.73 hard to find?

Shouldn't be too hard.

Do you have a pull it yourself type junk yard near by?

There are currently 26 square body vehicles in the one near me. $85 plus tax for a truck rear end no matter what type or gearing.

You just need to find one with the same lug pattern you have to make it a straight swap. You can put six lug axles from your truck into a five lug rear or the other way around too depending upon what you have as long as it is the same type of rear end (12-bolt or 10-bolt).

bitchin85 · 01-14-2010, 12:56 PM

just called a few places> two of them said they have none and two said they got them whatever ratio i can find for 125. and id imagine thats with me pulling it. it that bad? and im getting a vaccuum guage and a timing light soon and going through it all with a freind of mine. the truck starts real fast and easy even when its below zero and runs great. how much diferance will i notice if i go 3.42, or 3.73? will i be able to still take it on the e-way and do the speed limit?

68 TT · 01-14-2010, 01:17 PM

Quote:

Originally Posted by *****in85

just called a few places> two of them said they have none and two said they got them whatever ratio i can find for 125. and id imagine thats with me pulling it. it that bad? and im getting a vaccuum guage and a timing light soon and going through it all with a freind of mine. the truck starts real fast and easy even when its below zero and runs great. how much diferance will i notice if i go 3.42, or 3.73? will i be able to still take it on the e-way and do the speed limit?

$125 isn't bad. Go with the 3.73's if they have one.

With your 31" tires it will only be at a little over 2400 rpm at 60 mph.

72chevyk10 · 01-14-2010, 01:20 PM

it'll be wound up a little high but you should be able to do 60-65

just make sure you dont get 4.10s!!! like i got.. but i have bigger tires so its like 3.73s with 31s haha (not exactly but close)

bitchin85 · 01-14-2010, 01:21 PM

The speed limit in michigans 70.. But ill see what I can find. And I thought it was the higher the ratio the worse mileage?

68 TT · 01-14-2010, 02:22 PM

Quote:

Originally Posted by 72chevyk10

it'll be wound up a little high but you should be able to do 60-65

just make sure you dont get 4.10s!!! like i got.. but i have bigger tires so its like 3.73s with 31s haha (not exactly but close)

I'd kill for 4.10's the 5.13's are brutal without OD.

bitchin85 · 01-14-2010, 02:25 PM

Ya I don't want to go any biger then 373 I'd like to find a 342

72chevyk10 · 01-14-2010, 04:15 PM

Quote:

Originally Posted by 68 TT

I'd kill for 4.10's the 5.13's are brutal without OD.

yea i can understand that

. i had 4.10s 31's and a big block. it prety well toped out at 55mph

Quote:

Originally Posted by *****in85

Ya I don't want to go any biger then 373 I'd like to find a 342

id say a 3.42 would be the best for town and freeway. imo anyway

qu1cks1lver56 · 01-14-2010, 06:46 PM

i like my 3.42's
on the highway at 70ish (i think, no speedo at the moment) it's turning 2500-2600

3r!c84 · 01-14-2010, 07:45 PM

Quote:

Originally Posted by qu1cks1lver56

i like my 3.42's
on the highway at 70ish (i think, no speedo at the moment) it's turning 2500-2600

with what tranny? th350
i got that on mine and the same gears,at 65 its 3100

cableguy0 · 01-14-2010, 07:52 PM

A 3.42 gear should have you at 75mph at 3k rpm. if your turning 3100 to go 65mph you have a 3.73 or bigger gear.

3r!c84 · 01-14-2010, 07:54 PM

no was there when he was putting it in.and counted it.

my speedo was off but we had the gps on and it said 65 at 3k

pat386 · 01-14-2010, 07:58 PM

6mpg? even my peterbilt got better than that today at 80k lbs!

01-13-2010, 08:22 PM	#1
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	6 mpg... please help I got a long bed 2wd with a 355 with 305 heads, edelbrock streetmaster intake, edelbrock 500 carb, basicaly stock cam, stock distributor, mallory coil, automatic th350. Its got a 2.73 rear end and 31x10.5s... I know its no honda but I drive a lot and I think I should be gettin a little better milage. Also its real sluggish. Anyone have an idea of what It could be? Thanks guys __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-13-2010, 08:26 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: 6 mpg... please help the gears and that big tire are killing you. thats why its sluggish. you need to change gears. at least a 3.42 gear with that tire. its a mismatched combo from what you posted. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

01-13-2010, 08:26 PM	#3
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: 6 mpg... please help how much compression with the 305 heads __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

01-13-2010, 08:29 PM	#4
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help Ya I lknow it don't help. I had 275 55s on it and I was gettin about7 and I need a new rear end anyways so that's the next thing I'm gettin for it __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-13-2010, 09:11 PM	#5
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help Not sure about compression ratio but its gotta be up there __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-13-2010, 11:32 PM	#6
Benelli Watchin the rust grow Join Date: Oct 2008 Location: Western Nebraska Posts: 950	Re: 6 mpg... please help I'm feeling timing. yeah, the gears suck but I'd check timing, airfilters, plugs and wires, and maybe your driving? I'm not really sure. __________________ 1979 Chevy K10 (H/D Front end) - 350 w/ Holley Truck Avenger, Weinald Intake manifold, headers, bored .060 over, mild cam, Built up TH350 (TranStar Shift kit) with a part-timed NP203 t-case SOLD ($3,000) 1997 Chevy Silverado 1500 - 4.3 vortec, extended cab, 21 highway MPG, stock. "Red" SOLD ($3,000) 1987 Toyota 4wd Pick-up - work in progress, future DD SOLD ($1,850) 1998 Dodge Ram 2500 Cummins 5spd Quad cab - old 12 valve with some work done 2004 Chevy Silverado - Black, 4x4, 5.3L, stock for now Underneath that rust is a heart of gold

01-14-2010, 02:08 AM	#7
qu1cks1lver56 Registered User Join Date: Dec 2009 Location: Milton, FL Posts: 733	Re: 6 mpg... please help yeah check the timing, mine was off by 2 degrees and since i set it to where it needs to be it's freed up the motor and seems like the mileage has improved. also make sure your tires are aired up to 35-40ish up front and 30-35ish out back (depending on what the tires recommend) and if you were local to me i'd trade you my 3.42's for your 2.73's

01-14-2010, 03:31 AM	#8
Matt Man Registered User Join Date: Oct 2009 Location: Buhl, Idaho Posts: 1,438	Re: 6 mpg... please help put all synthetic fluids in your truck 3:73 rears, od trans new plugs wires check timing, tire pressure and most importantly check your hammer down foot. __________________ 86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11 1981 chevy K10 short Bed Scottsdale SOLD 10-26-2020 67 GMC Stepside Straight six/3 on the tree "The Peach" 2020 Silverado Double Cab LT Z71 5.3 8 speed Daily Driver K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934 The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903

01-14-2010, 05:09 AM	#9
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 6 mpg... please help Tune it up!! http://www.centuryperformance.com/tu...e-spg-148.html http://www.tuningmadeeasy.com/tuning...e-wonder-tool/ __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

01-14-2010, 07:14 AM	#10
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help The plugs wires coil cap rotor are like a month old so that's all good. And an OD trans juat aint gonna happen for a while. I usually drive it normal or baby it but sometimes I lay into it.. How hard is it to swap out the gesars or do I have to find a new rear end __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-14-2010, 10:04 AM	#12
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help Ok I'm going to call around later for a rear end. Is a rear end with 3.42 or 3.73 hard to find? __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-14-2010, 12:56 PM	#14
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help just called a few places> two of them said they have none and two said they got them whatever ratio i can find for 125. and id imagine thats with me pulling it. it that bad? and im getting a vaccuum guage and a timing light soon and going through it all with a freind of mine. the truck starts real fast and easy even when its below zero and runs great. how much diferance will i notice if i go 3.42, or 3.73? will i be able to still take it on the e-way and do the speed limit? __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-14-2010, 01:21 PM	#17
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help The speed limit in michigans 70.. But ill see what I can find. And I thought it was the higher the ratio the worse mileage? __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-14-2010, 02:25 PM	#19
bitchin85 Registered User Join Date: Aug 2009 Location: Lambertville MI Posts: 962	Re: 6 mpg... please help Ya I don't want to go any biger then 373 I'd like to find a 342 __________________ "I'll keep my guns, money, and freedom. You can keep the "change"

01-14-2010, 06:46 PM	#21
qu1cks1lver56 Registered User Join Date: Dec 2009 Location: Milton, FL Posts: 733	Re: 6 mpg... please help i like my 3.42's on the highway at 70ish (i think, no speedo at the moment) it's turning 2500-2600



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01-14-2010, 07:52 PM	#23
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: 6 mpg... please help A 3.42 gear should have you at 75mph at 3k rpm. if your turning 3100 to go 65mph you have a 3.73 or bigger gear. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

01-14-2010, 07:54 PM	#24
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: 6 mpg... please help no was there when he was putting it in.and counted it. my speedo was off but we had the gps on and it said 65 at 3k __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

01-14-2010, 07:58 PM	#25
pat386 misshape grape Join Date: Nov 2008 Location: the badger Posts: 385	Re: 6 mpg... please help 6mpg? even my peterbilt got better than that today at 80k lbs! __________________ Don't you just love rumors? I always find out stuff about myself that I had no idea I even did..

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