6 mpg... please help

[bitchin85]

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]

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]

how much compression with the 305 heads

[bitchin85]

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]

Not sure about compression ratio but its gotta be up there

[Manbearpig]

Originally Posted by *****in85

Not sure about compression ratio but its gotta be up there

Probably around low 8.3-8.7:1
Depending on what pistons you used.

[ironroad9c1]

Originally Posted by Manbearpig

Probably around low 8.3-8.7:1
Depending on what pistons you used.

Figuring if he kept the dished pistons, 305 heads usually spec out to 56 cc not 58 as advertised, typical .041 felpro head gasket stock bore, and a conservative guesstimate of .015 piston to deck height hes looking at about 9.3 to 1 CR not bad, but that edelbrock carb sucks find a good qjet and don't forget to figure out how far off your odometer is between stock tire size and the tires you are running now, and add that to the miles traveled . If you are running a single plane intake, rip it off and get a dual plane, Single plane intakes have no place on a street driven vehicle.

http://www.powertvonline.com/forum/showthread.php?t=964

[Benelli]

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]

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]

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]

Tune it up!!

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



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

[bitchin85]

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]

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]

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]

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).

[nekkidhillbilly]

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

be cheaper honestly to find a 700r4 used you can get em for like 200 bucks all day long here

[piecesparts]

Originally Posted by nekkidhillbilly

be cheaper honestly to find a 700r4 used you can get em for like 200 bucks all day long here

With the 2.73 geared rear end, I believe that you will be going the wrong way by going to a OD tranny. You will kill off the 6 MPG with the lugging on your drive train (been there, done that). Changing gears is about an $800.00 project (If you have someone do it for you) Changing rear ends is about the same, if you look for a good one (especially if you upgrade to a posi unit) and pay someone to do it. A complete rear end is something that you could do in your garage if you have air impact tools for the spring u-bolts and a way to handle the complete assembly under the truck frame. Rear ends with lower gear ratios can be found everywhere, especially ones W/O posi. Remember to rebuild the brakes when you do the rear end and look into getting the tranny's speedo gears updated for the rear end gearing change.

NOTE: An OD tranny is still a good idea, but do it as a combination, not just one thing and expect the best of results.

[bitchin85]

I'm going to start looking for a used performer. Would that give me any power gains over what I have now? Or mpg gains?

[68 TT]

Originally Posted by *****in85

I'm going to start looking for a used performer. Would that give me any power gains over what I have now? Or mpg gains?

It should give you both by moving your power band lower and increasing low to mid range torque.

[bitchin85]

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]

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]

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)

[68 TT]

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]

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?

[bitchin85]

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