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Old 03-25-2011, 06:36 PM
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Building a fuel economy chevy smallblock v8

I am building my 1981 Malibu to be a daily driver. I am not going for performance, but more just crusing and looking good doing it( lowered on 17s)

I recently found a single barrell carb and intake for cheap, The carb is even rebuilt. I would be bolting this on a 350 or 305. I have not bought it yet. I am curious if it is worth while for fuel savings over a 4 barrel running on just primaries.

What I am wondering is, if I drive the car on the primaries and do not engage the secondaries on my quadrajet, the 700r4 I have swapped in, will I see much savings swapping in the single barrell over a 1977 quadrajet 650cfm.


I could have the quadrajet tuned for economy right? what about synthetic oils in rear end and transmission... Those should make a difference to right?

I appriciate your wise wisdom towards this subject, I do not want to drive a new car, and am quite happy with my wagon as my daily driver soon.

PS: the current motor had water in the oil, the heads are rebuilt and decked, so Id like to use them as they are 416 58cc 1.84 1.5....If they check out after being pressure tested

The cam will just be a "RV Cam" as guys like to call em
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Old 03-25-2011, 07:06 PM
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Hi
That would be a 2bbl carburetor & manifold. Toss up as to weather you'd see much improvement if any from one to the other if you drive it the way you say.
Rich
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Old 03-25-2011, 07:08 PM
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It is one single barrell, one single butterfly. A 2 barrel is much wider and bigger.
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Old 03-25-2011, 07:58 PM
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Quote:
Originally Posted by GMMAN
It is one single barrell, one single butterfly. A 2 barrel is much wider and bigger.
I've never seen a 1 bbl. intake manifold for a SBC, if one does exist it would have to be off some type of industrial engine. I doubt very much it would give very good throttle response on a V-8. Without going to EFI it's hard to beat a Q-Jet for fuel economy. BTW, no such critter as a 650 Q-Jet, they were 750 and 800cfm with the majority being 750 BUT they only flow what the engine can draw. I would stick with a Q-Jet.

Get an '87-'91 LO3 305 TBI out of a passenger car, put the intake from a 4 bbl. engine of the same vintage on it with a well tuned Q-Jet, retain the EGR, put a set of 1-1/2" primary 4 tube full length headers on it with a TH350C (lockup converter) and 2.41 gears or a 200-4R and 3.42 gears and drive like there was a detonator for a Hydrogen bomb under the gas pedal.

You want a passenger car TBI because it has a roller cam and the much hated "swirl port" heads. Trucks had a flat tappet version of the same cam. The cam is what they call the "Peanut" cam. It is really small and for performance the heads suck but that combination makes great fuel economy. I have one in a full size 1/2 ton PU with a 700R4 and 2.73 gears. The engine is tired and the trans was weak and it still averaged 18.3 MPG. I just had the trans rebuilt with a lower stall speed lockup converter and am building a new 305 for it with some mileage/TQ modifications with 25 MPG HWY. mileage as my goal.
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Old 03-25-2011, 08:13 PM
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Didn't they make some with a 4 speed manual transmission?
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Old 03-25-2011, 08:16 PM
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i get between 15 to 19 mpg depending on jet size; 600cfm 4bbl, 362ci, 3:1 rear.

19mpg jets pushing lean limit on 362ci.

currently getting 15-16mpg on hwy w/ some lead footing.

getting true hwy milage is hard as counting licks to center of tootsie pop.

i was surprized milder cam did not produce better hwy mileage; did not rejet cruise mode because plugs are white post cruise.

plan to install wideband O2 sensor to fine tune one day.

1bbl 305E v6 GMC gets 10mpg on a good day.
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Old 03-25-2011, 08:37 PM
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Quote:
Originally Posted by Hippie
I've never seen a 1 bbl. intake manifold for a SBC, if one does exist it would have to be off some type of industrial engine. I doubt very much it would give very good throttle response on a V-8. Without going to EFI it's hard to beat a Q-Jet for fuel economy. BTW, no such critter as a 650 Q-Jet, they were 750 and 800cfm with the majority being 750 BUT they only flow what the engine can draw. I would stick with a Q-Jet.

Get an '87-'91 LO3 305 TBI out of a passenger car, put the intake from a 4 bbl. engine of the same vintage on it with a well tuned Q-Jet, retain the EGR, put a set of 1-1/2" primary 4 tube full length headers on it with a TH350C (lockup converter) and 2.41 gears or a 200-4R and 3.42 gears and drive like there was a detonator for a Hydrogen bomb under the gas pedal.

You want a passenger car TBI because it has a roller cam and the much hated "swirl port" heads. Trucks had a flat tappet version of the same cam. The cam is what they call the "Peanut" cam. It is really small and for performance the heads suck but that combination makes great fuel economy. I have one in a full size 1/2 ton PU with a 700R4 and 2.73 gears. The engine is tired and the trans was weak and it still averaged 18.3 MPG. I just had the trans rebuilt with a lower stall speed lockup converter and am building a new 305 for it with some mileage/TQ modifications with 25 MPG HWY. mileage as my goal.

I have to be honest, it did not look like a 2bbl. My first car was a 81 malibu with a 267 2 barrel. It had two butterflys. But, I did not look down the carb, it was round, smallish maybe 3-4 inches in diameter, compared to the 2 barrell I owned that was say 6 x 4.

Anyways, I have a 92 700r4 I am putting into the car. I am going to pick up a 305 out of a 1980 cutlass tomorrow. I know the flat cam song, so I am not even going to bother with the camshaft, and put in a new camshaft into the 305.

I think I am going to stay with my quadrajet. It is off a 1977 Manual Transmission car, so my guess is a 4 spd truck, but never know, maybe off a 4 speed car, although very rare.

Mileage is my concern too, and I just picked up Hedman shorty headers today for 30 bucks, sandblasted and painted. Going to wrap them in header wrap I have laying around.

What gear ratio is optimal with a 305/700r4 combo, you mentioned you run 2:73s, but how tall is your rear tire combo? I am running 225/45r17s that measure 24" tall. My gear ratio is unknown because I am hoping to swap to a 73-76 rear 8.5 diff. they are a few inches wider, which my rims kind of need to look perfect on the car, plus will help with the handleing being wider in the rear.


Now I just have to find a camshaft/lifter setup, or run the one I have( which is almost new factory GMC cam, pickup a few gaskets, and get the TCI lock up kit for my 700r4, modify my quadrajet for 700r4, find a radiator, mount my lincoln electric fan, install the quick ratio steering box,pump and pitman arm. Also, I need to make a new Y pipe from the shorty headers into the 2.250 exhaust that was already on the car, going to stay single exhaust, but putting a flowmaster delta flow I had laying around in the rear of the exhaust, its going to replace the factory muffler and have a 2.5 out coming off behind the tire.....


wish me luck gents

Heres hoping for early April test drive the way things are coming together












By the way, 4 barrel intakes factory, do not bolt onto TBI engines. You have to modify the center 2 hole locations on either side for it to work, and its kind of shady way to do things.
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Old 03-25-2011, 08:46 PM
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We will need some pictures of the build.
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Old 03-25-2011, 08:49 PM
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If you want cheap mpg's the best bang for the buck is a TPI 305. Mill the heads to raise the comp .5, put a good set of long tube headers on it, get a good valve job and clean up the bowls, single 2.5" exhaust, minimize accessory drag, run a 5 speed manual trans, lower it as far as you can, retune, and you could get close to 30mpg.

It won't be a screamer but it drives really well.
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Old 03-25-2011, 08:56 PM
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Quote:
Originally Posted by ap72
If you want cheap mpg's the best bang for the buck is a TPI 305. Mill the heads to raise the comp .5, put a good set of long tube headers on it, get a good valve job and clean up the bowls, single 2.5" exhaust, minimize accessory drag, run a 5 speed manual trans, lower it as far as you can, retune, and you could get close to 30mpg.

It won't be a screamer but it drives really well.

Buddy, that is not budget at all.

I am going to be into this car for 900 running and driving in 3 weeks.

you just spent 2500 in 2 sentances.

Ovbiously my budget, and your budget is compleatly opposite. thanks but no thanks
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Old 03-25-2011, 08:59 PM
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Quote:
Originally Posted by V8&4spd
We will need some pictures of the build.

Here is all Ive got right now, the engine/trans is coming out tomorrow, and the new 305/700r4 is going in. Then its time to work around the engine/trans getting them finished, along with exhaust off my shorty hedman headers.
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Old 03-25-2011, 09:11 PM
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I'm in this way less including the transmission. It was broken in with Walmarts finest $10 for 5 quarts oil. There is enough left over for a doodle bug when gas goes to 5 dollars a gallon.
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Old 03-25-2011, 10:05 PM
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what the hell is that? haha

It will be funny when gas goes up, and people complain about paying so much for fuel and are into there vehicles for 10, 20, 30 or 40 thousand dollars.

I will be into mine for 2000 with new paint job and rims, and I will have 18,000 to spend on fuel, haHAHHAAAAA
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Old 03-25-2011, 10:22 PM
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I get 30 mpg with a 02 merc w/all options what do you get?
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Old 03-26-2011, 09:43 AM
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carb ??????????

Hi,in 1964 i bought an Oldsmobile Convert,(new) with a 394 engine and a 2 brl carb,6 MPG (at 75 mph) swapped carb and manifold to a buddy that was selling his olds,for 2-4 brl carbs and manifold,same speed,12 to 13 mpg,go figure.
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