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Mileage Maker SBC? How to?

Discussion in 'The Hokey Ass Message Board' started by Harrison, Mar 9, 2011.

  1. alex211
    Joined: May 20, 2010
    Posts: 39

    alex211
    Member
    from NW PA

    Yeah, the nv4500 is way more trans than I need for a 2wd truck. I have the nv3550 in my jeep and it is a nice shifting transmission with good ratios, 145,000 trouble free miles so far.

    This is off topic but applies to what we are talking about. My buddy has a 77 f250 with a 400 ford and a 4 speed. It has 4.10 gears and 31" tall tires. We built the 400 with 9.5:1 compression, bigger cam, cam timing slightly advanced, msd ignition, dual 2 1/4 exhaust with fenderwell headers, edelbrock intake, edelbrock 600cfm carb, and scorpion 1.5 ratio roller rockers. He says it gets 13-14 miles per gallon which isn't bad for a 3/4 ton 4wd truck from the 70s. Stock those trucks were lucky to pull 10mpg.

    He could probably squeeze a little more economy by driving it nice, but it's always in the 4 barrels and will smoke the tires in 3rd gear easily. Just shows that building an engine that makes some power running on the edge of detonation will get you decent economy and be fun as hell to drive. The truck will hit the 5300 rev limiter in 4th gear with no problem, the engine seems to run pretty good.
     
  2. nxpress62
    Joined: Feb 8, 2010
    Posts: 20

    nxpress62
    Member
    from Kansas

    So occasionally someone will chime in and say the 700r4 isn't the way to go, and I don't think anybody is really listening. Maybe it needs to be put another way. Check out any Motors manual and look at the torque peak for a first generation small block chevy, usually going to be 3200 rpm or so for a 350 and only slightly less for the 3.75 inch crank 400. The engine will at its greatest efficiency (meaning less throttle opening to produce enough road horsepower to move the car at the necessary speed) at or near its torque peak, and carburated small block chevys do not run well below 3000 rpm, even with stock cams. Thats a good chunk of the reason all the high geared, overweight, overdriven (sometimes), under compressioned chevrolets of the late '70s and '80s got terrible mileage.

    I had a good buddy that had a 1970 GMC 1/2 ton lwb with a 300hp 350 sbc (10:1 comp, 3500 rpm torque peak) and 3.73 gears that would pull down 17 mpg at 75 mph while my 1985 1/2 ton with 2.73 gears and a low compression 350 would struggle to get 12 mpg, and he could whip me at a stoplight.

    The reason modern overdrives work so well is the tuned port, vortech, and LS series stuff is computer controlled and running lean at low rpms..
     
  3. nxpress62
    Joined: Feb 8, 2010
    Posts: 20

    nxpress62
    Member
    from Kansas

    Oh, also a guess about the guys who love their 305s. The 305 has the 350 crank (3.48 inch) and a smaller bore. The bigger bores can't help but suck more gas (bigger pump, right?) and will get worse mileage (ask any 454 chevrolet owner..) In theory, find yourself a mid '70s 267 (3.5 bore, 3.48 crank) and build it. 'Course you probably couldn't find decent pistons or heads for it.. What about a 305 with a 400 crank (think I saw a magazine do that a while back?) would work great at a lower rpm and wouldn't have the big bore to feed..

    BTW, the 5.3 LS motor follows this trend with a smaller than 350 (3.779) bore and a longer stroke (3.622), something that also enables it to work better at lower rpms.

    Oh, also all the quadrajet fans are right. I had a 325 horse 396 chevelle with a quad that would knock down 20mpg if you never, ever, ever put in the back barrels...

    Isn't bench racing fun?
     
  4. Deuces
    Joined: Nov 3, 2009
    Posts: 20,098

    Deuces
    Member
    from Michigan

    I think chevy made a 262 small block also with a 3.100" stroke... Not sure on the bore size..:confused:
     
  5. GVX
    Joined: Sep 18, 2011
    Posts: 2

    GVX
    Member
    from tennessee

    edited and repost
     
    Last edited: Sep 18, 2011
  6. George
    Joined: Jan 1, 2005
    Posts: 7,414

    George
    Member

    3.67
     
  7. GVX
    Joined: Sep 18, 2011
    Posts: 2

    GVX
    Member
    from tennessee

    I Want to put a SBC in a 1991 Toyota 4wd Hilux pu 4 cyl 5 spd with a blowed engine. It has 31X10.5 tires. Not sure of the curb weight maybe 3100-3200? I have several gear ratio's 4.10's,4.56's, and 4.88's to find the correct torq range. I been reading this topic and I think if I do a sbc conversion I will get as good or better fuel mileage than the original 2.2 engine. the conversion wont be terribly expensive bell housing,clutch, and slave cylinder kit about $600.00's. I have several engines and junk vehicles I have a 265 cubic inches SBC out of a 1982 olds cutlas it has a 3.48 stroke and a 3.5 bore. I want to mary it to a tbi injection out of a 1992 chevy van any thoughts if this is too small cubic inches,s will I get better mileage if I go with a 305 cubic inches? or maybe put a 3.75 stroker kit (400 SBC crank) making the 265 cubic inches into a 288 cubic inches (3.5 bore with a 3.75 stroke). The reason I am considering the TBI injection is it's easly do-able for me. I have Mitchel 5 and All-Data for refrence and I have been a certified ASE master tech for 35 + years. I have 3 complete vehicles with tbi's on them. I havnt done much research on the ecu yet but I am sure there is someone out there that can remap an e-eprom for me. Thanks guys I am looking forward for any helpful input
     
  8. Dude this is a hot rod forum.
     
    Matt Franklin likes this.
  9. nexxussian
    Joined: Mar 14, 2007
    Posts: 3,240

    nexxussian
    Member

    GVX, while a V8 swap fits in here, the vehicle doesn't.

    Not jumping on you about it, but please understand that it doesn't fit here, so lots are likely to complain.

    If you want to ask about technical issues of an engine swap, just say the vehicle is OT (off topic) for this forum.


    As for which engine I would put in that truck, probably the 4.3 V6, with the TBI that came on it.

    If I had to put a V8 in it, HO 305 would get my vote.

    If you want more specific information on swapping engines in that truck, check th Pirate 4X4 and Ih8mud forums.
     

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