Guys....I have finished a winter long project and with todays long drive i am getting 24-25MPG on a 12A Stock rebuild in a mazda Truck (B2000) using a Sterling 465 carb..

Here is the rest of the combo.
Rebuilt with .001 clearance on all parts including apex seals.
oversize apex seals.
Solid corner seals
12A old front and rear iron.
mid 70s middle iron with the small port.
1979 housings.
complete 79 rotating assembly with the heavy flywheel
I checked the compression today and it read 135 on each rotor..(crazy i know)
1979 tranny

dual 6AL MSD
2nd gen leading coils
1979 manifold with not emissions.


1990 toyota rear with 4.30s
26x8.5 street tires

Total weight 2700 (estimate)

will get some pics real soon

 

Wow that's some great fuel mileage. I only get about 20mpg with my Sterling. Of course I have it jetted pretty rich on a tired engine. What size jets are you running and whats your timing set at?

 

A header will help, as would some taller gears and a 5 speed tranny if you don't already have one. 35 mpg, sorry but I can't see that ever happening. I'm suprised you're hitting mid 20s, that takes some very conservitive driveing. The taller tires put your effective diff ratio at less than a stock 1st gen diff and tires.

Lowering the truck as much as possible, increasing tire pressure and removing the tailgate will help for a few more mpg on the highway. Won't do much around town.

 

Back when there was the Craftsman truck series in SCCA they found removing the tailgate didn't do much for aero. The back of the cab is a problem as much as the frontal area.

About the same time, GMC did a Bonneville truck and IIRC set a record with a stock body S15. The really cool thing that I remember from that truck was the bed cover. It was flat from about the wheel wells back, on top of the bed edges. The interesting thing was it sloped down to the bottom of the back of the cab(front of the bed). They found in the wind tunnel that as the air came over the cab it started to 'roll' in a horizontal fashion and filled the dead spot. The rest of the air traveled over the cab, over the barrel rolling air and off the back of the truck.

I've always wanted to do something like that to my Dodge Ram diesel to see what I'd get. There was also an episode of Mythbusters that covered the truck tailgate but I forget what they ended up figuring out.

 

I saw a Mythbusters episode that tested tailgate up, and tailgate down. Both with no bed cover. Tailgate up got better mileage. They tried a miniature wind tunnel to see what was going on, but it wasn't clear. So they made a liquid version using water with particles in it. You could see the particles rolling/swirling behind the cab of the little truck.
All those years I was driving around with the tailgate down thinking I was saving gas.

 

The most I have ever seen out of any of the 7's I have EVER owned was around 25. I dont know of anyone who has ever even seen 30.

I was getting 25 in my 7 which weighs exactly 2230 lbs. even, that was the best I ever managed. And that includes all the carb/ port/ exhaust/ ignition combos I have tried. I would imagine your truck will have a more difficult time reaching the 30 mpg threshold with its weight and aerodynamics. Granted I was never chasing fuel economy numbers, but good luck on your attempt. I think you'll need it.

Lowering the truck and narrower tires will help your aerodynamics substantially. And I must say, 25 mpg in even a small pickup is impressive for a 12a.

 

When I went to DGRR in North Carolina I got 18 mpg on the way down. While I was down there, Orion helped me throw in larger jets in the primaries (substantially larger). Lots more power and a happier car all around. Heading back to Michigan I averaged 21 mpg. And that's on a Sterling that is tuned for power, not economy.

The nice thing about the Sterlings is that you have so much flexibility. You can't swap out air bleeds in a stock Nikki. With that adjustability, and Sterling's writeup and support, I don't doubt that you'll be able to hit 30 mpg.

Good luck, and congrats on the great mileage you're already getting!




.

 

About a year ago I got 22MPG out of a stockport 12A with A Holley comander 950 4bbl (4 injector) TBI and 950 ECU and that was with a fresh tune up and 147 horses.....I miss that motor....

 

rotaryB-2000 is a long time friend of mine and has been using many of my carbs for a variety of applications for a few years now, including drag racing. He has a drag racing team, several drag cars pulling impressive numbers, and his own line of rotary engine performance parts. I think he knows about tire pressure & headers.
He came for a visit yesterday for a carby swap. I've stated for a long time that, with a stock port 12a and the appropriate timing & jetting, numbers in excess of 35 MPG should be possible. The Sterling Nikki can be jetted conservatively down low while still allowing for spirited driving up top, but such jetting configurations need to be done purely on a custom basis as it depends upon the driver's application, set up, and driving style.

-Of course, all of this is explained in great detail on my website...

 

I got 34MPG in the city. Don't be too quick to judge

 

shiettt, I got more than going downhill

 

The truck has a header to a 2.5 collector then about 20 inches of 3" tube to a borla Xr1 (early round series) then more 3" pipe to a primaflo muffler, Sounds real nice.

The truck has 4.30s so i can still move stuff around with th tow hitch but with 4.10s i should be at 28-29mpg...

I am playing with different timing settings due to the small center plate port combo.

truck has the rear leaf springs de-arched 3" and we also have a tonneau cover.
The stock 79Tranny with the 3.62s 1st gear and 2.20 second is just fine...5th is 1.1.

The only advantage would be a miata 6speed or rx8 6speed tranny..(maybe later)

Now guys this is lunch box NOT a rx7...I truly believe that a 1st get with 3.90s stock tranny and tall tires can see 30-35 all day using a sterling.

The nice thing with the sterlings is the emulsion setup...regardless what the engine needs as far as fuel goes it always has it..I have run my timing @55ATDC with my first sterling carb and as it needed fuel the emulsion tubes provided without leaning the engine out..Truck ran 14s with a lightly ported 12A.

You can see pics on the sterlingcarburators website..