[novaderrik]

take my 74 Monte, for example..
i know from experience that it is possible to get 30 mpg out of an old car- the old 76 Monte Carlo that i had in the early 90's averaged right around 30 mpg if i drove it fairly nice, and got 25 or so if i drove it like the 19 year old i was. and, yes, i verified the odometer on morethan one occasion.. it was actually a fairly quick car, too- i beat my cousin's 280Z by a few car lengths a few times, but my other cousin's 355/4 speed Monza killed me every time.
but how hard would it be to build a 350 that not only knocked down jap econo car mileage, but also put out very little emissions? i've read about people getting their cars smog checked and getting really low emissions numbers, but what's involved?
anyone have a good engine plan that doesn't break the bank?

 

[77 cruiser]

OK how did you manage 30 mpg out of that? Mine got 19 bone stock 305 with 2.56 gears did some mods headers, duals, intake & carb still got 19 now with the 385 3.73 & OD still gets 19.

 

[novaderrik]

i can't explain the mileage- it just happened.
maybe 2.56 gears and half the quarter panels and floors being rusted off had something to do with it- but it stil lweighed just over 4000 pounds at the local grain elevator scale. the motor was the stock 350 with a $139 northern rebuild kit in it with an old Weiand intake manifold that i had to use an adapter to mount the rebuilt q-jet carb onto it.
but i do know it that i could fill it up, drive 150 miles, and top it back off with only 5 gallons of gas. and it was a consistent thing for the whole summer of '93.
i want to recreate that with the Monte i have now, but the best it's ever seen was 20 mpg before i put the 700r4 in it- now it gets 17. i'm thinking maybe put the 305 from my 86 Caprice together and put that in there. that thing averaged 26mpg until the one head decided to crack.

 

[vrooom3440]

Maximize torque, minimize displacement, minimize fuel burned per time, and optimize the bejeebers out of it.

I would think a smaller long stroke motor with relatively high compression and EFI with a really good EFI manifold might do pretty well if you keep the RPMs down. You will need the EFI to get the AFRs down just right. Electronic spark control can help too to provide optimal spark curves.

Smooth long tube intake runners will emphasize low end torque as will small diameter equal length headers.

You will want to make sure it has an overdrive behind it of some sort. Figure 2000 RPM or less going down the highway. May also need to put some aero into the mix to actually hit 30 MPG though.

I have heard that the Corvettes often pull down high twenties on the highway.

 

[novaderrik]

i was thinking a 10:1 305 with a very mild cam would do the trick- my other Monte had the sealed power stock replacement cam that came with the kit- .390/.410 lift and almost no duration. it would idle silky smooth in gear at 400 rpm with 22" of vacuum. that thing was just amazing for what it was.
as for the aero thing, i've got the grill mostly blocked off- which alone was worth a couple of mpg. efi is kind off off the table- a good q-jet is what i'm using. already got the overdrive, but the stock low-compression 350 really didn't like that "mod"- it actually lost mpg everywhere except for going 80 down the interstate, and that stayed the same.

come on- any more suggestions. i'm willing to be a guinea pig here..

 

[vrooom3440]

Actually by aero I was thinking of adding some under-body to smooth the chassis. Front air dam, possibly side skirts.

If you can do it with a carb, a Qjet would be the one to do it with. If you wanna go this way I suggest adding a wide band O2 so you can tune it to the n'th degree.

I would also convert to electric cooling fans on a thermostatic control.

The 10:1 is probably a good start... I dunno the bore X stroke for the 305 but part of what I was thinking is to get the torque benefits of a long stroke while keeping the displacement down. A smaller bore will also reduce the hidden chamber volume to help promote complete mixture burn.

This is counter intuitive but cold air induction and clear flowing ports would be a good thing. Again produce an excess of torque so you can regulate it down as much as possible.

 

[Billy177]

well the ls1 cars get pretty close however I dont think that even they get 30mpg

 

[mike67sd]

I remember years ago a friend of mine said conversion to 100% alcohol fuel was not that difficult. My guess is that this would be more green from an emissions standpoint, which is the real problem with fossil fuels. The only problem with alcohol is that its not a very efficient use of the land used in its production, and to outright replace gasoline would not be feasible for this reason. For older, less efficient cars with the large engines this may be one way to clean up our act.

 

[Guest]

An 8 to 8.5 to 1 CR, 350 w/, if you can find one, an old E-brock 4-barrel, SP-2P intake and a 390 Holley 4-barrel using an adapter on it, a CC 246PE Pure energy cam, 1.5" dia., 4-tube really long headers, a 3-speed stick OD or a 4-speed w/ 2.56's should help a bunch, imho..

I'm afraid to tell you to use a T-5, 5-speed b/c they are WEAK!!

pdq67

PS., or if you can find one, the E-brock 2-barrel SP-2P and Rochester 2GC 2-barrel carb. instead of the 4-barrel.........

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[novaderrik]

Actually by aero I was thinking of adding some under-body to smooth the chassis. Front air dam, possibly side skirts.

If you can do it with a carb, a Qjet would be the one to do it with. If you wanna go this way I suggest adding a wide band O2 so you can tune it to the n'th degree.

I would also convert to electric cooling fans on a thermostatic control.

The 10:1 is probably a good start... I dunno the bore X stroke for the 305 but part of what I was thinking is to get the torque benefits of a long stroke while keeping the displacement down. A smaller bore will also reduce the hidden chamber volume to help promote complete mixture burn.

This is counter intuitive but cold air induction and clear flowing ports would be a good thing. Again produce an excess of torque so you can regulate it down as much as possible.

i tried a front air dam, but all it did was increase the frontal area and knock the mileage down from 17-14. i could tell the motor was working harder, because it had less vacuum at highway speeds. but it sure held the road a lot better..
i already have a home made dual snorkel cold air induction setup and thermostatically controlled electric cooling fan.
the dual exhaust made no difference in power or mpg over the stock single exhaust- it is a heartthrob 2 1/4" mandrel bent kit- the very same kit Summit and Jeg's sell as their house brands.
i MIGHT jump up to 3.42 gears from the 2.73 it has now, just to put a little less load on the engine.

 

[GRN69CHV]

First change I would make is a very small hyd roller cam with wide lobe centers. Aside from fuel injection, this one addition to moden engines has possibly had the biggest impact.

 

[Guest]

Back again, sorry, go w/ a 283 instead of the 350!!

And fwiw, that .390"/.410" lift cam mentioned earlier is the GREAT old stock, -929 hy-cam at 195/202 is a real winner in my book for a dead smooth torquey stock engine..

The next up is what is called the Performer" at 204/214, .420/.441" lift or so.

Cheap from Summit!!

pdq67

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[GuysMonteSS]

Gearing and RPM also has a lot to do with mileage.My big block cruises at 2600 RPM @ 63 MPH and will show you 16-17+ mpg,thats 550 plus HP,rectangular port head LS-6 big block.Not bad,all things considered !!
Guy

 

[novaderrik]

i might just order another cheapo Northern kit and throw it in the stock 350, and upgrade to the "performer" cam that pdq mentioned.
one of my friends has an 85 Camaro with my second Northern special 350 in it- but unlike the .390/.410 cam i used in the first engine, i used an Edelbrock Performer cam in it. it didn't have much power or get over 10mpg in the Vega i slapped it together for, but when i sold the engine to him after junking the Vega, it got 25mpg in a 77 Impala 2 door, and is now getting around 27mpg in the Camaro. and he has no idea how to tune anything beyond setting the timing to factory specs..
i was hoping someone had some "magic recipe" for a budget mpg motor- but it looks like i've had it all along. hell, maybe i'll even get this block looked over and bored if necessary. that would be a first in my series of "junkyard jewels".
but if anyone else has any ideas- please post them.

 

[Elcoman]

PS., or if you can find one, the E-brock 2-barrel SP-2P and Rochester 2GC 2-barrel carb. instead of the 4-barrel.........[/QUOTE]
I got better mileage going from a 2GC to holley 4010 and performer RPM manifold on a 327. The barrels on the primary are much smaller.
I did love my 2GC though, I could get many a races with it.

 

[gnicholson]

Stick with your Q-jet. get a wide band o2 like innovate to help you dial in the fuel mixture.Make sure you get your adv. curve dialed in with special attention payed to the vacuum advance; shoot for approx. 50 deg at light throttle cruise.I might build a 307 with original small chamber heads with good valve and set work for low lift flow or vortecs, 9 i/2-10:1 comp, good non egr stock Q -jet man.252-260 adv on 112-114 small tube headers.

 

[Guest]

The biggest deal is just putzzing around like an old-man!!

That's the best way to get good gas mileage, imho...

pdq67

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[novaderrik]

if you've got a good vacuum gauge and know how to use it, you don't need an O2 meter. the engine will tell you what it wants.

 

[Keith Tedford]

If your quadrajet carb has the power valve stuck in the down position, gas mileage will be great. Driveability won't be the greatest though. A friend's '68 SS396 Chevelle had this happen. Wouldn't hardly turn a tire but highway mileage was terrific. If you really wanted to go green, you could set the car up and run on straight alcohol.

 

[gnicholson]

Vacuum gage will tell you the load on the engine ;you can use it to tell you what circuit to tune in your carburetor. what it won't tell you is the fuel mixture .You can tune by drivability and by reading plugs and watching your mileage but o2 sensors are fairly cheap and they make the job much quicker. I thougt you were looking for ideas if you already knew it all I wouldnt have bothered you.