Thanks for all the info guys. Please keep it coming. From my quick read through the posts (I'll study closer later) this is what I've gathered: 350 Good-breathing OEM heads (suggestions?) Edlebrock Performer Intake (idle-5500rpm #2701) Q-jet carb size suited to engine (PN#/size?) Cam suited for desired RPM range Hot ignition & plugs Headders & free-flowing exhaust Electric fan 700R4 My rear is either a 3.08, 3.36 or 3.55 My tires have to have clearance for the air suspension so nothing too big there. Am I close? Thanks, JH
A free TH400 vs. a $100 700R from Pull-a-Part is worth the expense in my case. I can make up $100 at the pump in a hurry. I'm not talking Tremecs & Gear Vendors Overdrives here. Thanks, JH
OD transmissions don't have to cost alot. I bought a suburban and took the 350/700r4 then almost got my money back out selling parts off. I've been driving around town WOT, so no mpg just yet. But it hauls ass. If I ever put 15" wheels and wide whites on, the final drive would be better for mileage. the old 235 got north of 20 mpg with the t5 and a 2 barrel carb. Single exhaust.
In about 1982 either Crane or Crower came out with a high mileage piston + cam package for the SBC. I was a set of very high compression pistons (like 13:1) and a unique cam. It involved certain cam duration and overlap profiles that allowed it to run on regular gas. My manager at Ramchangers install the kit in the 350 in his 4x2 Chevy 1/2ton. It had real good power and made over 20 MPG average. I can't remember what it was called, but I don't think it was widely sold. Steve
that's true. i remember reading the gas mileage stats on similar pontiac V8's, the one with the 2bbl got worse gas mileage. that's because the primaries on those Quadrajets were small. open up the secondaries though and gas gauge falls faster than your speedo rises. there are a ton of tricks to eeking mileage from your car. the simplest however, are keeping your tires hard, shifting early and anticipating stops.... every time you hit your brakes, it turns gas energy into heat on your brake-pads..... go to; www.cleanmpg.com . those guys are the antithesis of the folks here. lol... they do some crazy shit just to eek an extra mile per gallon.
I'd go with a smaller engine. It's been my repeated experience that adding cubes reduces mileage. On everything. Really. Gearing is very important, but as mentioned the engine has to be set up to work with the gearing. Modern engines have a very flat torque curve, starting at very low rpm--they are designed to run efficiently at 1000 rpm. Watch the tach in a late model car/truck with a V8 engine, you'll see it's not spinning very fast at all. This is the key to good mileage. Go with overdrive, for sure. These recommendations are based on engineering principles I learned competing in the SAE High Mileage competition.
I'm thinking along similar lines, in teh 80's I had a '67 Nova that got a 283 for awhile, got almost 30 on the highway with a th350 and 3.08 or 3.55 gears ( I forget) It was all stock with the small 2GC 2 BBl & headers & 2 1/4" pipes turbo mufflers. I'm thinking going with the small V8, 283 or 327, power pack or fuelie heads, roller rockers, OD trans probably t-5. Now the things I was thinking of was going with a six pack using progresssive linkage, anyone done that and managed to mostly keep the other two carbs closed? ( kinda wonder If I could do that myself... ) I'm going to go with a '67 Camaro I think, I have one and they are fairly light. The Nova's weight helped the mileage alot I'm sure. ( anyone wanna swap a '67 Nova for a '67 Camaro? ) Cheers!
Last year I drove this to the round up 68 biscayne, 3:36 gears, 3 speed on the tree. I took a 283 out of a 67impala and did top end build since it had good compression. I used a set of 305heads from 81 truck motor, the 58 cc ones, a craigs list performer intake, an old carter 600. a crane energizer 266 cam, hei , duals. I got over 21mpg running at 2300 rpm. I took a old edelbrock carb and got the fine tune kit, jets and was getting 17mpg in town and over 20 hwy. People will almost give a way 283's here and 305 heads are cheap too. I probably didnt have $500 in that motor. Do you have clutch pedals already? I would build another motor just like that in a heartbeat. Maybe next time buy a 500cfm carb new. My bone stock 283 2bbl worn out oil burner in a 63 bel air with 3speed manual gets 17-18mpg hwy
The overdrive works @ highway speed, in town not much benifit, just figure how much highway is going to be done. You only want to drop C/R if it was high enough to require premium. Think the Econo-Performer used a Crower Baja-Torkmaster cam.
Ineteresting. It has been brought to my knowlege that someone here is going around giving ONE star to any thread mentioning SBCs..............we are onto you
someone over on an F-body site did the EFI tuning thing so that he could more heavily EGR his 350 TPI. I'm not advocating that particular intake manifold but he was pushing high 20s mpg on the highway.
My initial thought was "buy an S-10 and put the El Camino body on it". If you have the wheelbase right, think of how much lighter everything is. Frame, steering, suspension, etc... If you don't want to do that, follow the other decent ideas above, and try to lighten the weight somehow. (smaller rear diff, rack n pinion bolt in kit, aluminum heads, etc...)
Here's something I wrote about 3 years ago that you guys may find interesting. I just returned from a trip to Quebec Canada. It was a little over 2000 miles round trip, and I ran a little expirement to see what effects on economy I could get out of my van. The van: 1996 Dodge Caravan 3.0 litre V6 [gasoline burner] 3 speed non-lockup tranny 2 adult passengers [me and ex-wife], 2 suitcases, and a 4 lb package I was delivering The overall condition of the van is "good". The tires are about 50%, the tranny was rebuilt about 10,000 miles ago, and new plugs, wires, cap, rotor, and air filter were installed at that time. The rear valve cover gasket has a bad oil leak, and since the intake manifold must be removed to access it, I'v neglected to change it It leaks out [almost] exactly 1 quart per tank of gas. I'v gotten into the habbit of putting in 2 quarts every other tank. 99.9% of this trip was expressway driving. Filled it up and left out of louisville. Did absolutely nothing to it, just as a soccer mom would be driving it. Speed limit thru Ky was 70, set the cruise control @ 75 and drove non-stop untill the low fuel light came on. First fillup, mileage avaraged 20.972 Thinking this was a little odd as I remembered this van getting about 23 mpg, I started looking around, and found the rear passenger tire to be SERIOUSLY low. I aired it up to 32 psi, and hit the road. The speed limit thru Ohio was 65, so I sat the cruise on 70 mph. We detoured off the X-way 1 time for a bite to eat. [less than a mile] Next fillup, MPG averaged 22.484 So... Setting the pressure in all 4 tires @ 32 psi and dropping the speed 5 mph netted me a 5% increase in economy including a pit stop. The gears in my head were turning, so I overinflated the tires to 45 psi and hit the road, and again kept the cruise @ 70. No pit stops this tankfull Next fillup, MPG averaged 24.217 Shortly thereafter, we crossed in to Canada. The speed limit was 100 kph, or 62 mph. I was sorta getting into the "economy" thing, so I set the cruise @ 66 mph. 2 pit stops and the delivery this tankfull. total of about 4 miles off X-way Next fillup, MPG was 25.388 It was time to add oil. I bought a container of Lucas oil stabilizer and poured it in. I only added 1 quart this time because them crazy canuk's overcharge like crazy!!! The fillup cost me an additional $17 over a fillup in the states, and the Lucas was $19!!! Back on the highway, cruise varried between 65 and 70. Ran into some traffic congestion, and about 15 miles of speed up - slow down city driving. Made 2 pit stops. Next fillup, MPG was 24.165 I was a little dis-appointed in that figure. I had kept the speed down, and the city congestion had not been too bad.... Hmmmm..... I wonder if the "thick" lucas was taxing the engine..... We stopped for dinner, and I swung into an auto parts store. Bought 2 quarts of Mobil-1 0-w-30 "econimy oil". I NEVER run synthetic in this van because of the oil leak, as expensive synthetic just leaks out faster, but for this little expirement, I figured, what the hell...... I also bought an off the shelf Fram air cleaner and a bottle of Gunk 1-tank injector cleaner. Poured in and installed all the goodies. Filled it up with BP super-93, inflated the tires to 50 psi, rolled up the windows and hit the road. Set the CC @ 70 mph and made no pit stops. Filled up just after we crossed back into Kentucky... Are you ready for this? MPG averaged 30.902 mpg. As we were driving thru downtown Cincinnati, the ex-wife was commenting on how [extrordinarily] long we had been running on this one tank. She was "getting into" the expirement as well, and when she saw the 31 mpg figure on the calculator, she gave me a big kiss and we did a victory dance right there in the gas station parking lot... I hope nobody was watching! Conclusions: Make sure your tires are properly inflated. Overinflate them [at your own risk] for even better mpg. Slow down... Just a 5 mpg reduction makes a good difference. Tune it up, and replace your air filter Synthetic oil consumes less HP to pump it thru the engine Premium fuel might actually be worth a few extra cents Now I hope you were paying attention to all of that. I went from 20 mpg all the way to 30 mpg, a full 50% increase in fuel economy simply by inflating the tires, tweaking [and tuning] the engine, and slowing down. <!-- / message --><!-- sig -->
Maximum efficency is achieved at your engine's torque peak, so choosing a cam and rear gear ratio that "come together" at the cruise RPM will give you the best results. Another consideration is the engine itself. Long stroke engines produce more torque than short stroke engines. Tho some people might consider it a sin, the 305 and 307 SBC has advantages over a 283 or 350... Consider for a moment that GM actually made those engines in the face of mileage considerations... 305 H.O. heads are a good choice. A 242 or 252 crane cam, or Isky mile-a-more with a set of Rhodes lifters, and an edelbrock aluminum 4V intake with a well tuned Q-jet cant be beat. Small tube headers with a full exhaust that includes an X or H pipe will further boost both torque and MPG. Spend a few extra bucks on a good ignition system. I like the MSD stuff personally. Keep the compression as high as possible [for the street] and run premium gas. Higher compression "squeezes" the air/fuel charge harder, and causes a more violent explosion,,, basically it extracts more power from the fuel. The .20 cents a gallon you spend for premium will pay for itself in the form of better mpg since your extracting more power from the same air/fuel charge. Add a water injection system just to be on the safe side if you want. The 700-4R is a fine tranny, but a 200 R4 consumes less HP. All the little things add up quickly, and if you think the whole thing thru, you can assemble a max-mpg combo on the cheap if you hunt and choose those parts that most hot rodders shy away from.
These trucks are as aerodynamic as a brick! I'm running an EFI 305/700R4, 3.42 rear, 235/75R15 I get 18-19 mpg. Not bad, but I had hoped for better. Rich
Oddly, I have a 63 Biscayne with a 292 6 Cylinder (with duals, an Offy 4bbl with Edelbrock 500 carb, and HEI), the stock 3 speed trans and rear end (don't know the ratio) with 205/75/14s for tires. 75 MPH is just about 3000RPM. Loaded with 6 people and a trunk full of stuff, I can get 20MPG at a steady 65MPH. Given the motor is set up for low end torque, if I had another gear, I'd probably pick up at least 2 MPG. The aero stuff discussed prior makes sense, and i'll probably try a thing or two before summer to see what works...although the car is already really low.
That is true for work done vs fuel consumed. In a diesel, where the torque is low, around 1600 rpms, that would be were you want to cruise, however in a gas engine, even one like mine that was built for torque as low in the rpm band as possible (516 lb/ft @ 2800), 2800 rpm would not return near as good fuel economy as 1900 rpm. If powering a generator at full load, then 2800 would return the best kilowatts per weight of fuel burn. I have two diesel vehicles, 2000 F350 6 speed, and a 2001 Excursion automatic. Both weigh around 8000 lbs and both are 4X4. If driven at 1700 rpms on the freeway (62 mph) both get over 20 mpg. The highest I've got is 26 mpg.
Found some info online for this system... 'The "Crower Mileage System" may be more familiar to some of you as Mazda's super-Japanese-tech "Miller Cycle." The Crower kit used a mechanical compression ratio in the mid-teens, via highly domed pistons. They matched it to a cam with a very late inlet closing, bleeding around half of the intake charge back into the manifold on the compression stroke. So you had a 350 that looked more like a 200 on the intake stroke, and a 350 on the power stroke.' I remember is worked good, until it wiped a cam lobe. Afterwards, he built up a 350 with the B&M supercharger kit. Steve
i messed with this a little a few years back on my model a...set the timing with a vacuum gauge and drove with the vacuum gauge. had it running @ 17" at around 65 to 70mph....jetted the 600 holley down some and put a hotter thermostat in it. never did get to install the msd ignition at that time. i know i was giving up some mpg running 315/55/16 sport trucks , but didn't have a pair of 30" tall skinnys laying around. lightweight wheel & tire package helps as well....
200R4 trans, same dimensions as th350 or close enough not to have to cut driveshaft, it has a little shallower first gear than 700R4 but less drop between 1-2 shift. shift kit and stock converter. 350, low tension rings, single timing chain, standard oil pump, hypereutectic pistons, windage tray, deburr/ polish tops of pistons to eliminate heat points for higher compression possibilities. set your clearances to run 5W30 oil. Vortec heads make great power everywhere in the powerband, youre kind of lift limited without machine work or beehive springs but for a mileage motor you arent going to exceed that. Best Power for the $, find a good used set and do a boild / seat clean up and run them. does require a special intake that adds about $50 over standard chevy intakes but its worth it. Do a mild clean polish up of chambers / under valve and valve intrusion into the runner. compression, run as high as you can on 87 octane, if you go with vortecs you get a much more efficient combustion chamber and can push compression to at least 9.5 or 10:1 small Q-Jet or maybe 600 edelbrock with electric choke, good ignition, HEI will give you lots of tuning options, on a dual plane intake. fresh air intake, and carb plate to keep heat out of carb, can be plastic 1 5/8" headers, 2 1/2 exhaust with cross over Torque Cam / RV cam, want to keep your lift under .450 duration (at 50) under 210. Look at Crane Energizer 260 / 266. Depends on rear end gear, this will set your cruise rpm, want to match your cruise rpm best to peak torque on your cam. higher numeric gear will push cruise rpm up, you will go with a little more duration. I like rebuild kits from northern auto parts, they sell elgin cams with vey similar specs to the crane RV cams and every time I compare prices Northern has always come in as a good deal. Tune the hell out of it. Buy an HEI spring / weight kit its worth the $ if you take the time to dial in your timing curve, jet the carb, with each timing change,
JH...alot of good comments ideas here...I think an overdrive trans is the way to go... I would go with a 305 or a 307 which has a longer stroke that equals more torque in a slightly larger cubic inch size...headers with dual exhaust, good ignition and maybe a small runner aluminum intake like a SP2P intake with a small Holley....those intakes are dirt cheap at the swaps... X2 on the 283 vs 305/307..you need torque with an overdrive trans to cruise at 1800/2000 rpm or so..
When I was a kid I worked at the local Chevron station. One of the regular customers sold concrete steps for homes and had two samples he carried around in the bed. Probably 500-750#. His truck was a 1975 Chevrolet with a 350, he was so disappointed that the new truck only got 6-8 MPG when his old 70 with the 350 got 12-14mpg and had more power. The guy went to the junkyard, pulled the heads, intake and carburetor off "the oldest 283 he could find", had the heads worked and 2v Rochester rebuilt, put them on the 75 350, first tankfull was 13mpg. Sucky mileage for this day and time but a 5mpg improvement was worth the trouble and investment. I think the smaller cubic inch, smaller ports keep the torque up and stock 283 2v cam is the way to go.
This comment may be inapproprate, but a manual gear box gets better mpg than an auto due to less parasitic drag, or do you specifically want to or need to use an auto box for some other reason?
You could always go the route that Plymouth did with the 76 Feather Duster.... Slant six One barrel carb 2.94:1 axle special exhaust aluminum inner hood, inner trunk, bumper mounts, intake manifold and transmission housing 36 mph
Totally agree, have changed several automatics to manuals. With everything else left unchanged, simply changing to a manual shift is generally good for about 30~35 percent. In other words 20 MPG stick, 13~14 MPG automatic. Don't know of any engine mod that will make this kind of difference. Jon.
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