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Gas Friendly Performance

Discussion in 'The Garage' started by tecton, May 18, 2003.

  1. tecton

    tecton 1/2 ton status

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    New air filter, new oil, new fuel filter, new bosch platnium +4 spark plugs and wires, headers, some kind of after market cam, timing advanced to 6, dual glasspacks, edlebrock 600 carb, rpm weind intake, 3.42 gears and 33x12.50 mud tires.

    Thing drives like a rv full of fat people.

    I can switch down to 3.73 gears ( need top speed and gas milage) what other things can i do, that wont suck my wallet at the pump but give me more lowend. perhaps a 650 holley carb (ive heard edlebrock sucks) new fuel pump, new distributor...any other ideas?
    Mabye switching my glasspacks for flow 40, or 50's?

    Tires stay
    Probably a 4 inch suspension lift when i get the money (thats all for this truck as far as big mods) But it is and will be my DD. Need to cut the weight or get a supercharger or something...
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    don't go with 3:73's go with 4:10's with 33's thatway you can still go up to say a 35in tire later and you will notice a big difference with 4:10's /forums/images/graemlins/thumb.gif
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Good gears are where it's at, they multiply the torque coming in by the ratio so the deeper the gears the more torque is seen at the wheels. 3.42's are fine for 26" tall street tires, but for 33's you should go deeper. If you have overdrive I'd consider 4.56's, 4.10's at a minimum. With 4.56's you'll be turning about 2400 rpm at 75 mph in OD, and it'll have a ton more low end snap./forums/images/graemlins/cool.gif

    That rpm is still low enough to net you decent mileage too...

    For comparison your current gears net you about 1850 rpm at 75 mph...which is lugging the motor IMHO.

    As for off idle snap let's assume your motor makes 250 lb/ft or torque at a fairly low rpm and peaks at 300 lb/ft. With 3.42's the torque at the wheels would be 2600 lb/ft of torque and building to 3150 lb/ft at the torque peak. With 4.56's it would be 3488 lb/ft and build to 4100 lb/ft at the torque peak.

    That is quite oversimplified, but you get the idea. It's also quite a significant change.

    Rene
     
  4. tecton

    tecton 1/2 ton status

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    been thinking of doing that anyway

    my dad keeps telling me, cause i have an automatic...that if i get 4.10's or 4.56's that i wont be able to hit 60mph and will just "be paying more to use more gas"

    my vehicle is my DD and i drive ALOT...i think i drove 3k miles this month alone.
    Ive had it since feb and it had 600 miles on it...and last night i turned it over to 9k
     
  5. MousePowrd

    MousePowrd 1/2 ton status

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    Doesnt your Dad know what overdrive is? Cant hit 60mph? WTF
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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    an engine has a sweet spot, with your cam, you are probably nowhere near it. Engine will run more efficiently closer to that spot....
     
  7. SUBFAN

    SUBFAN 1/2 ton status

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    That thing will NEVER get 30 mpg /forums/images/graemlins/grin.gif
     
  8. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    I've got the same setup with the 700R4 and 208. I ran 33's with 3.73 for about 4 years. It was a pretty descent setup, but it was a dawg on the hills. Had great getup and go. I could hit 17 mpg on long road trips. Never had a problem.

    But, you should definately consider the 4.10s if ya got a lot of hills to do.
     
  9. tecton

    tecton 1/2 ton status

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    i dont think ive ever been in OD...never got up there

    atleast i dont think so

    what kind of change should i expect changing from 3.42, to 4.10...neck jerking?
     
  10. MousePowrd

    MousePowrd 1/2 ton status

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    [ QUOTE ]
    i dont think ive ever been in OD...never got up there

    atleast i dont think so

    What kind of change should i expect changing from 3.42, to 4.10...neck jerking?

    [/ QUOTE ]

    Cruise control will work much better, all gears will be closer together so acceleration will be constant, less shifting by the tranny in normal driving. It wont be like adding a supercharger or anything, but it will make EVERY ride in the truck more pleasurable
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Pick your gears so that in OD you are in the sweet spot (2200-2400) at your normal speed. A small block will run all day long at 2800 so 2400 isn't going to hurt it any.

    Even with 4.56's you should be able to pull 100 mph...(4700 rpm in drive, 3300 rpm in Overdrive) so freeway speeds wouldn't be a probelm at all. You should see 33% more torque at the wheels with 4.56's over your 3.42's...what other mod short of NOS could you do and see those kind of gains?

    Rene
     
  12. tecton

    tecton 1/2 ton status

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    im not trying to race it, but if i wanna go i wanna go...gotta outrun the ex gf's!
     
  13. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    3.73 gears with 33 inch tires is 2730 rpm DRIVE at 70!
    4.10 is 3k at 70 in OD.....How fast are you planning to go? 3k is well within reason at 70mph in Drive. In OD with the 4.10's you will only be turning 2046. Hell I would concider 4.56 since you have overdrive. Taking the load off the engine and the transmission is going to increase MPG. It's also going to help keep you from frying that 700r4.
    http://www.ring-pinion.com/calculators.shtml
     
  14. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    I think I would try and advance the timing a bit. At six degrees BTDC it probably would feel sluggish. My motor likes 12 degrees. I set it back to 8 and couldn't get it to go 60 mph.
     
  15. tecton

    tecton 1/2 ton status

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    no more than 70...tires are very knobby and hwy driving would wear-em out fast
     
  16. Thunder

    Thunder 3/4 ton status

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    I'd go with the 4.10 gears and maby consider switching back to a Qudra- Jet carb. Q-jets usually will get better milage than Edls or holleys. Also the smaller primariy venturis will increase air velocity at low RPM. giving you more torque on the bottom end of the RPM band.
    If you plan on lifting you may expect to loose a mile or two per gallon due to increased air resistance.
    I would also try advancing the timing to 8 or 10 degrees and see how that works. most chevys like to run around 10 degrees.
     

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