70 mph @ 2000 rpms is what Detroit is giving us in spades. Must have some merit to that gearing. However, if your ride is 1790 lbs, and your torque peak is at 2800, then you can gear even taller than that. At 70, I think I'm around 1700.
no guessing with the mileage here: kept accurate track for the numbers provided: my 5500lb year-round daily driver/parts chaser suburban 4x4 with a TBI 350 SBC, 4L60e... if i'm easy on it i get 13mpg around town, 15mpg on the highway under 63mph (2000 rpm on the nose). if'n i'm driving it like im angry... 10mpg around town. TBI motors suck. i keep threatening to put vortec heads on, shitcan the TBI and run a quadrajet. had a junk yard 307 that i didn't even do a rustoleum rebuild on, dropped it in a '62 1/2 ton truck, with a 3spd OD. wouldn't win any races but 26mpg at 70mph with a bunch of stuff in the bed was the norm. 28mpg if i was trying. had a 283, 10:1, generic PAW RV cam, 3 2bbl with progressive linkage, in a 1900 pound car, with a T5. 3.23 rear, 760/15 tires. as long as i paid attention to my right foot, it was an easy 29mpg at 65mph. 22mpg around town was easy. never really tried to get great mileage... meaning i did play around with it a bit. i'm planning another 283 SBC for my '31 model A. side note, for the spool comment above: my kinda OT "more fun" daily driver has a spool... very hot 4cyl pushrod motor, 4spd, 2200lb pinnacle of 60s swede performance. drive the hell out of it, no issues. no broken axles. only a slight scuffling around tight turns. 10k miles/year like that, in any weather. i've had spools in plenty of street cars. never had a problem. throttle position is everything... my last daily had a spool as well: the wife put about 40k miles on it... she never noticed the difference.
my dad remember's readin car and driver or somethin like that when he was young, a new '59 biscayne with a 283 and overdrive 3spd with a stock rear end like a 3.36:1 or somethin like that got about 28mpg back then!! that impressive for a car that big. 283's are my dad's favorite small block chevy.
i think a spool could work on the street if you're careful. The reason why i was suggesting was for someone who wants to squeeze every last mpg out of their setup; There are much better ways to improve mpg, but every bit helps. The idea is to reduce weight in general and reciprocating mass.
get a 283 with a 700r4, that th400 might be free or cheap but it takes some Horsepower to turn it and it doesnt have an overdrive. and from the sounds of it the 700r4 will take anything from what ever motor you choose to bolt infront of it. got a buddy with a stock 283 2bbl and 700r4 (not sure on the rear end) but hes getting 20mpg highway.
Mt O/T 1980 El Camino with a tired 350, Performer Intake, no cats, true dual glasspacks, un-gapped plugs, and crusty Quadrajet-backed by a Turbo 350 and 3.08 gears got at or above 20mpg highway, and between 15-18 in the city. I was impressed when I done my math, and kept trying to recalculate, but it comes out the same everytime. I give it just enough pedal to get up to speed, and feather on and off as neccesary to maintain 45-60mph.
Pick up any 86-90 camaro / frirebird with a TPI/TBI, use all of the powertrain out of it. Small CFM carb (380 Holley if you choose), retrofit the 700r4 with a lockup pressure switch.
i've been thinking about this with my TBI 350. it's a *great* running motor, but the TBI sucks... runs very rich at the oddest times. i'd be willing to bet a decent gain could be made with a quadrajet. i used to run a 350 with an Isky cam that was a few steps away from an RV cam (still kinda lumpy), Edelbrock Performer, carter 600, 10:1 forged pistons, light rods (swap meet find, no idea on the brand), cast crank, 1 5/8 headers, dual 2.5" with a cross over and Edelbrock mufflers... 700r4 with the lockup switch... in a full size 3/4 ton... it got a good 22mpg on the highway at 70mph. got 16mpg from LA to Phoenix with a tandem axle car carrier and a 5000lb caddy on it. this was close to 20 years ago, though... not sure how the difference in today's gasoline would effect those numbers...
Here's my combo, 305 with 9:1 compression, solid roller cam .525 lift, ported heads, 1.94 intake, 1.5 exhaust. Ported stock Q-jet manifold, heavily modified Q-jet to work with that camshaft. Basically stock balanced bottom end, saginaw 4 speed, 3.36 gear. I averaged 18 mpg driving 1000 plus miles round trip to Bonneville. The car would do a lot better with a five speed but that's not in the budget. This is all in a heavy chevelle. It hauls ass btw. You could do a lot better with a smaller roller cam, but a Q-jet is definitely key as well as the 305's bore and stroke. I also removed all the accessories from the engine, I have one belt for the alternator and a flex fan, an electric fan would probably be an improvement also. Good luck.
Gang, I have an '09 Chevy HHR SS with a FWD I-4 that makes 260 hp and 260 lb-ft of torque. Most road tests give it a 0-60 time just a tick over 6 seconds and around .9 g on the skid pad. In this fun but heavy 3300 lb car I get 22+ mpg city and around 30 mpg on the highway (over 30-31 mpg at 70mph, but only 27 mpg at 80 mph or so). I've heard of new high hp V-8's with 5-6 speeds that can match my highway MPGs, but of course not do quite so good in the city. I'd like to know ifn anyone can come close to my HHR numbers with a "305-ish" SBC. 20 mpg highway won't get it for me, from any engine / tranny combo. Gary
I am trying something new to me and decidely non HAMB friendly - so I will leave the hood closed at shows. I bought a 94' Buick Roadmaster with a LT1/4L60E that I am pulling out complete to drop into the 57' Savoy I picked up. In the roadbastard it was getting 28mpg all day long in that really heavy car, with 2.93 gears and goes pretty good.
http://www.summitracing.com/parts/TCI-376600/ Allow operation of the lockup torque conveter with out a computer.
my first a sedan had a setup like this...my transmission guy talked me into it, worked pretty good and what sealed the deal was the no computer required. had something like a 2600/2800 convertor with 370's and a mild 355. that car was way faster than my coupe i have now
Ok, an update & questions..... My 305 TPI has no computer with it. I'm thinking I'll ditch the TPI unit & run a Edelbrock Performer intake and Q-jet carb. Does anyone have suggestions on which Q-jet I'd need (part numbers would be greatly appreciated). As for the trans, as stated above, I have no computer. It looks like the lock up kit eliminates the need for a computer but what does it do? Specifically - & simply - what does a trans do when it "locks up"? I'm not pulling a trailer with this and I'm running an automatic because I want it to be just that - automatic. If I install this kit, is that the end of it or am I somehow in control of when it "locks up" (whatever that means)? I know NOTHING about an automatic trans. Clearly. Thanks guys, Jim
on the Intake, GM made carbed aluminum intakes for the 80-86 engines and for 87-90- namely in the chevy trucks. You might be able to get the intake at a pull-your-part for as low as $25.00 The torque converter is what "locks up" to give a near 100% transfer of power without slipping. It can increase mileage and cool down the temperature of the transmission, prolonging clutch, belt life.
arrison what gears are in your rear end? 3:36 or 3:55? Either will be good w a od. Do you have a q jet already? If not pick up a edelbrock carb used cheap and jet it down. I did that and got really good mpg
I don't know about the rear gear in mine. It is in West TN at Kennedy's shop & I can't talk him into going under there to retrieve the numbers for me. He is damn-near worthless. I have secured an Edelbrock Performer intake. Don't have a carb yet but I'm looking for one. Quadrajets are cheap & I did find a $45 Edelbrock 600 that needs rebuilt. Just not sure which I'd rather use. JH
PS, yeah a little but power brakes? Unless you drive around with your foot on the brake, which some people do, it's not robbing the engine of any vacuum when it's under a load. The engine sees it's highest vacuum under deceleration which is when you normally would be using the brakes.
If the car was originally auto it's probably got a rear end gear 3.36 and if it was standard trans 3.55 is more common. Either gear will do well with a od trans. If you can get a qjet cheap and a edelbrock cheap play with both of them and see which one you like.
Mine has one pedal, a shift lever on the column, & no evidence of the trans tunnel ever having a hole in it. Pretty sure it was an automatic. JH
327 sbc rv cam 600 cfm edelbrock saginaw 4 speed 8 in.ford with 3.00 gear at 65 mph gets me 23 to26mpg all day long on interstate. In town 19 to22mpg . 29 tall rear tire .39 ford sedan.At 65 ,,2250 rpm
Really? I have a fresh, fully ballanced .60 over 283 (292c.i.?) with a mild cam, flat-top pistons and a 3x2 with just the center 2bbl going most the time, dual exhaust, to a th350 and 8 inch with something like 2.75 gears in my '40 Ford pickup and don't get anywhere near that. Pretty much same tires in back too. Might be the auto trans? Or might be that I don't have a speedo or working gas gauge to tell me what's going on accurately. Or maybe it's just that I like the drive the shit out of my truck - ?
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