So, Can you have a Old-Style carbed V8 and get 25+ MPG?

We are now at $3.90+ for HotRod Premium

 

Man, a station here in town is charging $3.99 for 87 octane.

I think a 2-bbl 389 Pontiac with a manual trans and a 3.08 gear in a 3000-3400 lb car would pull 25 MPG. A well-worn (75,000) mile one with one cylinder compression off from the others did 18 for me, with a 4-speed auto (no OD), in a 4000 lb car. And was still tons of fun to drive. Pontiac sold an "economy" version of that motor for a few years, I think in '60 they won the Mobilgas Economy Run with that engine at around 21-22 MPG. It was basically the manual trans motor (8.6:1 compression instead of 10.25:1).

I've read claims of 25 MPG out of an early Studebaker V8, too, the 232 or maybe 259. I'm sure it can be done even more easily now, if you could get a 5-speed behind it.

Just dump the power steering, AC, and anything else that robs power from the engine along the way, and go to an electric fan if possible.

 

A long talk w/friends who tune the newer Euro cars, tells me that it's time to try the sensor/ecu world. So with no small sense of regret I agreed to consider the newer systems. Engine: 2.0L Duratec fourbanger. Trans: Ford/Mazda M5OD Total drivetrain package weight: ~340 lbs.
Alloy is used whever possible in the car. Total weight is aiming for about 1200 lbs. Steel rails, A roadster body and some form of light IRS for out back.

 

The 2.0 Duratec is a nice little engine. You might want to be aware that Ford has 2 different 2.0 I4's. The Zetec and the Duratec. They also have a 2.3 Duratec (mid-2003 and all 2004 Focus, reportedly, and mid-2001-up Rangers, Mazda B2300 and 2005-'08 Escapes - ~150hp) and next year they will have a 2.5 Duratec (2009 Escape - 170hp).

Zetec has intake on passenger side and exhaust on driver side. Duratec is the other way around.

 

4.09 to 4.19 for high test here. I've had several small block fords and chev that got about 25 mpg. Also a 455 Olds that got 21. It's not always about the size of the motor compared to the efficiency of it. Right now my 55 has a HO 305 with a Crane 274 cam, edel. performer intake and edel. 600 carb. Hooker super comps, M-22 4 speed and 3:73 rears with 29 inch tires and I'm lucky to get maybe 15 on a good day .

 

huh? lot's of "fuel cost" related threads here as of late.


spot the 2-bbl intake on this particular engine?

here's a hint... "he knows"

I hear ya' brah... but when I was driving 72 in a 65mph zone today and a woman in an Expedition passed me like I was standing still I said to myself "self---folks jus' don't seem to care... do they?"

Stay tuned for my "should they bring back the "double-nickle" thread.

 

I read as many articles as I can find on air/fuel ratio. For a carbureted engine, experimenting with jet sizes to lean the idle circuit out to 13.7 to 14.5 to 1
can yield some really good numbers. Wide band O2 sensors are the key. Regular ones are not sensitive enough to be accurate. The trick is to lean it as much as possible without hitting the dreaded pre-ignition. The difference between a 12.5 ratio and a 14.5 to 1 ratio is 18% less fuel burned. Different engines have different tolerances for lean conditions.

A lot of mistakes are made when calculating gas mileage. Just because the pump shuts off doesn't mean the tank is full. I always take the time to trickle fuel in until I can visually see the fuel level. My daily driver returns 30 - 31.4 mpg consistently on road trips but its a 4 cyl Chevy. I was amazed when just replacing the air filter after 20K picked up 1.5 mpg. Underinflated tires dropped mine to 28 mpg once also.

 

I will be happy with 15mpg out of my pontiac.

I willl be trying some tricks to get it better however. Headers are the number 1 thing you can do to improve fuel economy.

 

a buddy from here and i were talking the other day about something like this...the little 350 in my coupe has a 600 holly and edelbrock intake...hei ...etc...nothing special... i was thinking of leaning the carb way down ....and throwing a msd box on it...the car runs cools...(no thermostat....only lasted 8 months before it went bad) i was thinking if i could lean it to where it would run warmer,say around 180-190ish) ...would it work...? also been kicking around throwing the 2bbl on it...(ironicly...i gathered up the 2bbl conversion stuff for last a sedan when gas was getting near 3 bucks in 05)

question.1. how low can one go with a holley 600 jet wise...? before it doesn't work...

question 2... how much would headers help?

question 3...any of those crazy trick spark plugs help ?

just asking..... brandon

oh yeah...and i want it to run in the 12's too.....

 

I was just thinking ahead about this today. getting close to time to fire up the 283 in my 32. when I put it in I was figuring on running 3 97's straight linkage. that's ~450cfm. It's a very mild motor with an "RV cam" that I don't know the specs on and 2.02 valve 461 heads. I'm running 2" ramhorn manifolds on it. have about 8:1 compression. I'm thinking about changing to a factory GM four barrel manifold (iron/alum????) from the early 60's and putting a 500cfm AFB on it (edelbrock) instead. anyone have any ideas if this would improve mileage at all?? This is a "temporary" motor until I can swap in something that I really want. I'm not looking for HP out of this engine as it has early ford driveline behind it. HP=busted driveline.......

I figure if I put the afb (a factory carb in the early 60's) that I can make the motor look like I pulled it out of a wreck and put it in my hot rod.

 

Brandon,
As per your HotRod Chevy 350:

1. Holley 600 jetting: I've seen as low as 52 primary jets used, just depends on the overall engine combination. You may have to tweak the squirter cam to get it all to work out.
2. Headers will always be more efficent, keeping the primary side taylored to the engine operating range. 1 5/8" primary tubes seem to be the best for the 350 on a street engine.
3. "Trick-of-the-day" spark plugs do not work. A fine wire tip spark plug will "strike" much easier and puts less stress on the ignition system. A HEI or High Voltage ignition system will improve drivability. Stay at or near the factory heat range.
4. 12 second ET's are achievable, just use a 2.79-3.00 rear gear to keep the highway RPM's as low as possible, and use a transmission with a good gear package to accelerate your HotRod. Maybe use a 2004R or a 700R4 to have the best of both worlds.
5. Your camshaft choice should be one that helps produce low-to-midrange torque.

I will be doing this with my Coupe in the near future and I'm going to logg the proceedures, performance and mileage improvements.

 

will try a couple things.... the car is in need of a set of valve springs now....so it may get a cam/lifters/spring combo...ran the car a couple weeks ago.... went 13.50's at 96 mph...shifting at 4600 or so...(tach was only showing 3500...the msd shift lite came on with a 4600 chip...) thats with 2.76 or so gears , thru the ram horns and small 2 1/4 down pipes... a little tweaking will get me the whole package... man this is reading like a old hot rod article... thanks brandon

 

Brandon,

Chevy High Performance magazine did a feature on leaning out the idle circuit on a 350 Chevy like yours but I can't find which one. The thrust of the article was you can have your cake (up to 25 mpg economy on the street) and eat it too (wide open throttle performance) by concentratiing on the idle circuit alone.

The factory target for 12.5 to 1 A/F ratio isn't to improve economy. It just happens to be where the lowest overall emmision numbers fall. If your car is not subject to EPA regulations there is room to significantly improve economy at the expense of dirtier tailpipe emissions by leaning it out. Some engine packages can stand a 15 to 1 A/F ratio without detonation. That's 25% less fuel burned per mile.

The Vortec heads Chevy put out in it's 1996 truck engine lineup was an engineering project designed to pump up horsepower AND fuel economy. They feature streamlined port velocity, tight quench to improve combustion, swirl-design combustion chamber, and new design lobe profiles of the rollerized cam and wider lobe separation angles. The net effect was about 30 more horsepower in a 350 and about 2 more mpg as I recall.

Torque cams by definition have very little overlap but they make up for it by taking advantage of faster ramping of lift. Headers will usually improve fuel economy but If you run a cam with a lot of overlap and tight lobe separation angle I can imagine a scenario where it would hurt economy rather than help.

I know very little about spark plug differences so I have nothing to offer.

 

Fat Hack, Won't the Fleetline be way to heavy for the power to weight ratio using the Vega engine causing the vacume to be way high Sucking the Arabian Gold to EXCESS ???---CJ.

 

Brandon,
Getting your short-block to accelerate quickly will be a major piece of the overall success. Items that contribute to this are, camshaft lobe centerline, valve springs, ring seal, intake manifold design, correct carburetor modifications, and total ignition advance in @ 1200 RPM.
This is why a NHRA Stock Elimintor engine works so well.

 

as far as cam c/l.....what would a person be looking for...? at first , i was thinking of a cam swap ....but the more i think of it ...i might just swap in a small dish 355 i have ....it has a pair of 94-95 ish truck heads with 1.94's...not sure that the 1.6 roller rockers would help or hurt? got a small dual plane intake as well as a weiand stealth... will probably try the carb and ignition tricks first.... thanks for the help...brandon

 

another senerio....what would a aluminum rod and lighter rotating assembly do in a econo package....? just throwing out a " what if" deal.... thanks brandon

 

Strange that this post has just come back to the top of the pile.

Over the weekend my brother got married and I used my car to take the bride to the wedding and then the happy couple back to the hotel after the deed was done.

All told I travelled just under 500 miles from Friday through to Sunday, admittedly most of it on the motorway.

My wife asked me on Sunday night how much I had spent on petrol, quick look through the receipts showed £100, which equates to just under 20 Imperial gallons. Didnt think much of it until I worked out that I was getting just under 25mpg.

Car is a 56 Chevy Sedan. Engine spec is as follows

454 +100 with approx 9.2-1 CR

Crane 292H Cam

Edelbrock Performer RPM manifold with Holley 830DP with 74 and 76 jets

Oval port heads with a good port and matching

1 1/2 headers

DNE 4 + 1 trans with 3.25-1 gear in a Ford 9"

29" tyres.

Most of the driving was done around 2500-2800 rpm with about 50 miles on country roads, the remainder on the motorway as I already stated.

Even if I have got my maths slightly wrong it is still over 20mpg.

Just a shame that I spend most of my time with the tach on the red line trying to break things and getting less than half that.

P.

 

My 40 pickup has a 2001 explorer 5.0 converted to carb. Those engines come with a torquer grind hydro roller cam and the GT40P fast burn style head. Edelbrock performer intake, T5 trans, 3.56 gear with 29" tires. The math says it will be turning about 2000 rpm @ 70mph in 5th (.68 od). I have a Holley 570 street avenger already but most of the tuners and dyno people tell me the edelbrock 500 would get me better drivability and gas mileage on this stock engine. I'll try both carbs and whichever performs the best, stays, and the other goes right back where it came from, ebay. My goal is 25 mpg and that doesnt seem unrealistic.

 

35 ford pick up....327,stock rebuild ,,,a old new in the box Crane Fireball hyd cam, in the garage port and polish job on the heads,,,roller rockers , headers, 3 x2s ( junk yard carbs) turbo 400 (ykes a lot of lost HP) 3.00 posi 9-inch on the turnpike @70mph 23 mpg........... not bad, 39 2 dr 350/350 4bbl about 20 ish WTF still gonna drive em,,,,, I will just have to cut back on beer money,

I'm to fat anyway.

 

I routinely got 23-26 hwy mpg with a 224 cu in Studebaker V8 in a '55 Champion sedan. It had 3:31 gears and a T-86 with overdrive. It had a Carter 2bbl on it. Fast, it wasn't--but this same set up with a bunch of polished aluminum (a 2x2 intake, offy valve covers, etc) in a light car could ABSOLUTELY get a solid 25 mpg and still look bitchin' . .you could even run a Holley 390 4bbl on an aluminum intake and get 25 mpg.

 

bring this back up to the top..... todays subject....power valves...never really messed with them...usually replaced them with a plug and a bump up on the jets...higher number or lower, to lean ? anyone....??? thanks brandon

 

Well, you're killing your mileage by plugging the PV & bumping up jets.

PVs are typically vacuum operated (at least the ones that tend to get plugged) and open at a pre-determined vacuum level.

There is no "richer or leaner", merely opening sooner or later. You typically want them to open at least 1" below cruise vacuum level. So rig a vacuum gauge & go for a ride, check your cruise vacuum level, then subtract an inch and round down to the nearest 1/2" and that's the PV you want. So if you cruise at 9" of vacuum, you want an 8 PV.

This is just a ballpark starting point...some folks like 1.5" less than cruise vacuum, some 2".

 

the plugging deal wasn't on my street car... i'll dig the vacuum gauge out and see what is going on ...thanks brandon

 

here it is guys, the WHOLE trick. MATCH YOUR COMPONENTS!!! not really known in the small block chevy world anymore because you can just bolt shit on. whoopty-doo.

engine;
461 olds, 10.7:1 compression, KB hypereutectic pistons, stock rods and crank, performer 455 intake, modified q-jet, stock exhaust manifolds with true duals and glasspacks, big valve G heads mildly ported and polished, cam (custom designed for the application) 274/282 .499 lift 108* lsa installed at 103.5*, built th350 trans (didn't like this engine ) and a 2.41 ratio axle. 400ft/lbs at 1800rpm, peak of around 520ft/lbs at 3300rpm, tick over 400hp.

14mpg arount town with a highway gear in a 4000lb car with my heavy ass foot in it. never did get to test the highway mileage because of the trans dying behind that monster in 6 weeks. now i'm putting a different (custom designed again) cam and dual quads and sticking it in front of my model a. i'm expecting low 20's on the freeway with a 3.23 rear and a switch pitch 400 trans fairly easily. put a little thought into what you're putting together and it's easy to do...just don't expect every bolt on to be an effective boost in performance and economy. stick that torker on your worn out smogger truck engine, but don't cry to me when you lose your bottom end and mileage goes out the ass

oh yeah, it ran on 91 octane pump gas

 

Lot's of good idea's and combinations out there ........

 

So very true ..........

 

Switching to lectric waterpump and fan wont save fuel !The power they draw will still tax the alternator with about 5hp ,so no free lunch eh .

 

If that is true then please explain how late model Mustangs pickup between 10 and 15 hp at the crank with a switch from a standard to a fully electric water pump.

 

It's hard for trucks to get good fuel economy. The physics of pushing that brick through the wind is a bitch. but you could get quite close with you combo. Let us know.