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Mileage Maker SBC? How to?

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

  1. 1oldtimer
    Joined: Aug 21, 2003
    Posts: 7,995


    go with a quadrajet, small primaries, large secondaries.......waaaaay better mileage then a square bore (and a kick when floored). also the center bolt valve cover motor takes a different intake then the older motors.
  2. 1oldtimer
    Joined: Aug 21, 2003
    Posts: 7,995


    the 283's aren't really made for torque so the rpms window is small for fuel economy. if the rpm's are too low (for the curve) then you end up wasting fuel and if it's too high you'll burn fuel too.
  3. OldBuzzard
    Joined: Mar 8, 2008
    Posts: 878


    My '92 Roadmaster (TBI) 4200 lbs curb weight, got a regular 22 around town in cold weather, 25 around town in warm weather, 28 - 29 trip in the Northeast. Out West where you can run faster, 31.9 mpg with the car loaded (back seat out for more room for junk) cruising 75+. It has 2.56 rear gears, 700R4, Chev 350 engine. No slouch in the get up & go dept either.

    I have 3 of these cars/drivelines in the yard. Transplant material.
    Last edited: Mar 27, 2011
  4. woops, my mistake.. I meant p/s, a/c. Brain fart on my part.. I wish I could say it won't happen in the future, but I'd be wrong once again!
  5. Swifster
    Joined: Dec 16, 2006
    Posts: 1,449


    I'm going to tell you exactly what you don't want to hear. You will never make the same mileage with a SBC as you will with an LSx. Won't happen. Get a 5.3L and 4L60E from a late model pick up and drop it in. No muss, no fuss. You can get stand alone harnesses for both the engine and trans. Just because of aerodynamics, I doubt you'll ever get anywhere near 20 MPG. But that trans will let you run a 3.42 rear end and get real good mileage.

    And a carbed engine will not operat more efficiently than EFI. Just not happening. Yeah, yeah, yeah all the bullshit about an LSx not being traditional blah, blah, blah. No one in 1958 said they wouldn't use a 265 or 283 because it wasn't traditional. Part of the LSx that helps with mileage is that it's all aluminum now. How much weight does that pull off the front end? How much HP does a SBC fan use to run, even with a clutch? Or running a distributor off the cam.

    Mounts are available to bolt this in your Cammy. Just do it and enjoy the driveability and better mileage.
  6. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,346

    c-10 simplex

    i'm not disagreeing at all and i'm intrigued; Where else, besides being aluminum, do you think the LS'es get their efficiency from? For instance if you were to put a carb on an LS engine, it would still probably get better mpg than a traditional gen 0,1, or 2 small block. Conversely, the modernized EFI system of the LS could probably be adapted to the SBC ( i think dart or brodix has done it). In this case, the LS still gets better mpg than the small block.
  7. Swifster
    Joined: Dec 16, 2006
    Posts: 1,449


    The heads/combustion chamber are unique. Keeping the heat away from the intake manifold. The crank triggered ignition. The light weight of the powdered rods and the pistons. You could probably put LS6 heads, cam & intake on that 5.3L and make close to 400HP real cheap and not even effect the mileage (that engine makes up to 325HP stock). GM was claiming 20MPG with that engine in a heavy Silverado. How much would it cost you to try to convert a SBC to make the same HP AND get the same mileage. $1500 would probably get you a good used engine/trans combo that will last 200K.

    By the way, that 5.3L is approximately 327 CI. The 325 HP rating is SAE net HP, not the old gross horsepower used in the 60's. Don't want A/C? You'll probably get an extra couple of MPG.
  8. I'm not against an LS and yes, they do make cheap horsepower - just not as cheap as I want for this project. Regardless, this isn't the place to discuss LS swaps. There are plenty of other forums for that.

    Thanks, JH
  9. seanbelushi
    Joined: Jan 26, 2011
    Posts: 175


    Harrison, if you decide to ditch the TPI setup, I may be interested in it. Lemme know what you think.

  10. RacerRick
    Joined: May 16, 2005
    Posts: 2,753


    Don't forget the LT1 either - they are cheap, no slouch in power, and bolt up to traditional transmissions and engine mounts. I have a 94' roadmaster I am using for a drivetrain. Thing gets up and goes pretty good for a 4800lb car with 2.93 gears and gets mid 20's in mpg.
  11. Best bang for the buck on a budget is a 305 with 700-R. RV cam, 2.79 gears and a quadrajet. I put one in my son's 51 coupe and it performs well and gets mileage. The one in his 80 Malibu 2-door was just as good. It was a 305 with turbo 350 and a lock up convertor. My buddy used a 60,000 mile 305-700-R out of an 86 Caprice with a 2.79 ratio ford rear and even without an RV cam it performs great and gets great mileage in his 37 ford flatback. Performed flawlessly on the way to back to the 50's in St. Paul last year. 11 hours one way. Every car I have pulled the 305 out of and replaced it with a 350, I was sorry I had done it. Mileage dropped like a rock. For the marginal increase in horsepower it wasn't worth it. Just for the books, swapping an Edelbrock for the quadrajet doesn't help gas mileage either. I travel lots so am a big fan of the 305-700-R. I don't need neck snapping torque as I am looking for a good reliable, reasonably quick, fuel efficient carbuerated small block on a budget. Travelling here is measured in hours. Pat.
  12. fiveonechevy
    Joined: Jul 23, 2010
    Posts: 11


    My 51 Chevy coupe gets mid 20's on the highway with a 305/700R4 combo. I don't know what the gearing is, but at 65-70 my rpm's are at around 2300-2500 with converter locked up (i have a toggle switch mounted to dash to engage lockup). Also has MSD and Performer intake with Edelbrock carb. Super reliable with ok performance. I would recommend this inexpensive setup through my experience.
  13. badspeed
    Joined: Jul 18, 2011
    Posts: 1

    from America

    Looks like I'm ressurrecting a near-dead thread for my first post. Forgive. I was steered here by Google, searching for Project Mileagemaker, about a '74 z28 buildup done back in '74.
    Looking through this thread, I see a lot that agrees with my own experiences, but a lot that seems flat impossible. There's more than one way to skin a cat, but damn.
    So let me correct one bit of wrongness, then let me share a couple of my own experiences as examples of MPG.
    First, as great as the modern V8s are, and I own one, ( '01 5.3L ) the reason they do MPG is they precisely control the fuel and spark. They are making the most possible TQ, every second, no matter how little you're opening the throttle.
    But they have no MPG advantage over a properly adjusted Q-Jet, for one simple reason. EFI forces a 14.7:1 A:F ratio, ALL the time. For emissions reasons, EFI cannot run at a leaner 17:1, like a good QJ can.
    Now, on to what I've found.
    First, I had this '78 Camaro. 350, 700R-4, 3.08:1, 235/60R15s, 5" rear spoiler, #416 heads, LG4 intake manifold. Centrifugal advance not working. 6 degrees initial timing, 20 degrees vacuum advance, Painless Wiring lockup kit, and mandrel-bent 2.25" cat-back with DynoMax "California Boss Turbo" muffler. At a steady 65 MPH, that got 25.1 MPG. I couldn't believe it. So I turned around and went home. Yep, 24.8 MPG. I was so thrilled, I never checked it again. But I didn't realize then that my centrifugal advance wasn't working. I only discovered that a week before selling the car.
    Later, I had a '91 Camaro RS, with the TBI 305, 700R-4, 2.73:1, 235/55R16s. Pure stock and perfectly tuned, with about 115,000 miles. Only mod was a Flowmaster muffler. I drove it that way, every day, for 4 months. Always averaged 23 MPG. Then I swapped to a 3.42:1 axle, and with that, had to correct the speedometer. It stayed in OD more, with less downshifting. Another 4 months later, it was still averaging 23 MPG. But that rear started whining, so I swapped in a 3.08:1 gear, and fixed the speedometer. MPG rose to 25.
    Now I have an '83 C-10 2WD std cab long bed pickup. 6.2L diesel, 700R-4, 3.42:1, 235/75R15s. And a utility shell. With the overdrive not working, it does 24 MPG at 55 MPH. So I replace the transmission, remove the shell, replace the missing airdam, drop the tailgate, and go for a weekend trip.
    My best tank was 30.3 MPG. Now I want to swap this into an '82-'83 Camaro, with a 2.73:1 axle and 215/65R15s, and see if it can do 35 MPG.
    This is relevant, because at Pick-N-Pull, you can get 6.2 diesels all day every day, for $165. Add a transmission, the price goes up by $125. So for $300, you can be over 30 MPG. That's gotta be worth it.
    And 130 HP sounds slow, but you honest to God would not believe the way this truck jumps across intersections. Part of it is the torque converter, left over from my '91 Camaro above. But it is not frustrating to drive.
    One more. My current daily driver. '06 GMC Sierra WT1500. 4.3, 4L60E, 3.23:1, 245/70R17s. Even with a tonneau cover and a 2" drop, still won't top 20 MPG. This is stupid! My old '94 would do 23. But it had 3.73:1 and 235/75R15s. So I swapped a 4.10:1 axle into the '06, sent the computer out for speedometer correction, and go driving. It now does 22 MPG, mostly due to less downshifting.
    Last edited: Jul 18, 2011
  14. mustangsix
    Joined: Mar 7, 2005
    Posts: 1,297


    not true.... Factory EFI maps don't just stay at 14.7, they vary from very rich for full power to very lean for economy.
  15. Jon1953B4
    Joined: Nov 26, 2010
    Posts: 85

    from MD

    I have the TCI lockup kit Installed on a 70 chevelle with a 383 and a 700r4.

    The trans guy installed the module internally and left me one wire for a switch.

    I can't tell you what it does technically other than "lock" the free spinning clutches in the the converter.

    But real feel it acts as a overdrive or extra gear.

    At 75mph at 3000rpm's, switch the overdrive on and drop the r's to 2300.

    Less engine wear and better fuel economy.
  16. brandon
    Joined: Jul 19, 2002
    Posts: 6,334


    true roller rockers...not a roller tip
  17. Harrison,
    My small block makes over 400 hp and has consistently gotten 20-22 for around 100-130K.

    I have covered my build several times here on the board or at least the basics of it. You can purchase everything but the heads but there are comparable heads out there. Drop me a not if you want.

    The main thing is free breating and as much compression as you can get away with.

  18. Graham M
    Joined: Apr 17, 2011
    Posts: 406

    Graham M
    from Calgary AB

    Just a quick question for the guys that know, what kind of MPG differences can I expect between a Tremec TKO500/600 VS. A 700R4?

    I've read somewhere that 1.5" exhaust is condusive to better fuel economy then would be a larger diameter (lets say a 2.5") exhaust. Anybody notice this? I've never fooled around with this so I wouldn't know.
  19. Exhaust restriction does not help one breath. If it can't breath it cannot properly or efficiently burn fuel.

    The mileage you get from either transmission depends on how you are geared what RPM range your engine is built to perform in and your driving habits/ability.

    If you are good at shifting gears and keeping your engine in the proper RPm range then you will do better with the TKO. If your shift points are set properly you put it in drive and leave it and you are not well adept at keeping your engine in the proper RPM range and shifting gears you will do better with the automatic.
  20. grm61
    Joined: Oct 19, 2009
    Posts: 179

    from Washington

    Tough to go wrong with a 305 and 200r4...This 9 pass pontiac wagon we had for a few years got 17-19 in town and 21-23 at a 73 to 85mph cruise.

    305 Q jet 240,000 miles 200R4, dont know what the gears were, but it was long legged.

    Pretty good for a big ol boat of a car.

  21. George
    Joined: Jan 1, 2005
    Posts: 7,413


    You can get too little engine in too big a car. Got better milage in a '69 Charger with 383/727/3.23s than with a '69 Plym S/W with a 318/904(don't remember the rear gears, probably 2.76)
  22. alex211
    Joined: May 20, 2010
    Posts: 39

    from NW PA

    I am getting ready to build an engine for a ad chevy truck this winter. I have a 77 350 long block I pulled from a truck at the junkyard. I was wondering if the stock heads will work well for pulling some mileage out of the engine? I was already planning on flat tops, aluminum intake, q-jet, mild cam, and tuning the HEI.

    The transmission I plan on using will be a NV3500 from an 88 up chevy truck. I'm going to be buying a AD chevy truck to put the engine in this winter. I was just wondering how well the stock iron truck heads will work for me. thanks
  23. Pir8Darryl
    Joined: Jan 9, 2008
    Posts: 2,488


    '77 350 heads should be about as "average" as they come. Should work fine for building an economical engine... The NV3500 on the other hand is going to suck up some power to spin it. That's one hell of a heavy [and heavy duty] trans. Also, that a truck has all the aerodynamic properties of a barn door........... You can build it as efficently as you want to, but dont plan on being impressed with your overall MPG.

    Look at it this way.
    Right now you can go down to the Ford dealership and buy a new Crown Vic with a V8 that gets 26 mpg on the highway. The F-250 with the exact same engine will only get 16.... Just saying.
  24. brandon
    Joined: Jul 19, 2002
    Posts: 6,334


    Get some vortec heads.....will make nice power & torque. You wont be disappointed
  25. plym49
    Joined: Aug 9, 2008
    Posts: 2,797

    from Earth

    What aftermarket aluminum head is equivalent to a stock GM iron Vortedc head?
  26. Rudebaker
    Joined: Sep 14, 2007
    Posts: 1,598

    from Illinois

    I think you're thinking of the NV4500, the NV3500 (aka Getrag 282/Muncie M51) is fairly lightweight, I lifted one in and out of the trunk of my Grand Am no sweat and I have a bad back and knees. They also used them in the 4.3 S-10's for a few years and they are anything but heavy duty. Nice smooth shifting trans, just don't beat on it. 1st gear is 4.016 to 1 and OD 0.729 to 1.
  27. gwarren007
    Joined: Apr 3, 2010
    Posts: 381


    Edelbrock E-Tec 170cc
  28. gsport
    Joined: Jul 16, 2009
    Posts: 678


    i didn't read this entire thread, so this may have been mentioned already...
    i'd put a vacuum gauge on it to monitor how you're driving and try to keep it at it's highest vacuum reading. that'll tell you when you got your foot in it..
  29. davidh73750
    Joined: Apr 21, 2009
    Posts: 1,565


    Rod and custom had an article on improving drivability and mpg, saying to match your gears for od, ie don't use an od with a 2.73 but more like keep it at 3.36-3.73 to keep in your good rpm range. They also discouraged against aluminum heads, not sure why never ran any on a V8.
    I think my next mild motor I will run in a car I'll grab a vacumn guage do some highway driving and mark down the best vacumn and that cruising speed, make a note of the rpm and next car show drive or cruise drive it at that and see what it does for me for mileage.

    I had a bone stock 77 3/4 ton 2wh 350 4v, 350 trans, 3.73 and 235/85tires. I had the quad rebuilt, put in a hotter coil, dual 2.5 exhaust, drove it home on 105 mi trip and got 15mpg. I was impressed for that big lug.
    Joined: Nov 22, 2005
    Posts: 7,591

    from SIDNEY, NY

    True, I've got two S10s with NV3500s. One's starting to make some front bearing noise but, with 314,000 miles on it, I guess it's entitled.

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