Carbruator for best gas mileage
 

I have a stock 350 crate motor 250hp with a 700R4. I'm running 300 gears posi 9" and going to put 20's all the way around tires will be 255/45/20 in my 54 Chevy 1/2 ton truck. I'm trying to decide what would be the best Carbruator to give me the best gas mileage. I got a 670 4 barrel duel feed Holley street avenger. Holley said that's to big to go with there 570 street avenger. Edelbrock said to go with there Edelbrock performer series 600. I wouldn't mine have a little power, but over all I want good MPG.
I'm not building a hot rod, I'm a nice street rod that I can drive everyday and take trips in. I don't have a heavy foot and would like to see low 20's if possible on the HWY.
Also I'm building this truck on a budget so I don't have a bunch of money to throw at it, if I did I would have bought a LS motor with EFI. With that said what would work best for what I want?

Thanks

Re: Carbruator for best gas mileage
 

I would like to read what is suggested.

Re: Carbruator for best gas mileage
 

I'll be interested to see what is suggested also. My '54 was a daily driver until recently when I took it apart for frame-up painting. It also has a 350 crate motor with Edelbrock carb. I have checked the rear end ratio but I got about 16mpg with tires that are too big for the truck.

When it is back on the road it will have 7R15 tires on 6" wide rims.

In 2004 I bought a new GMC SWB step side that was tricked out by Regency with 20" wheels. I didn't care for the look and sold them and put the GMC standard size aluminum wheels on. My gas mileage jumped from 15 to 19 even though going down in tire size makes the odometer spin faster.

So that's something to think about when you're going for the big wheel/low profile look. Another plus to the regular size tire is they cost half while they last twice as long.

Re: Carbruator for best gas mileage
 

I have 20's on my dodge nitro and I get 22 on the hwy and so far I have 72,000 miles in them and still going strong. I know it's a new SUV, but for me I won't go with anything smaller. I was going to put 22's on until I found out I had to put 35 series tires on and I don't want to feel everything on the road.

Re: Carbruator for best gas mileage
 

quadrajet. the end

Re: Carbruator for best gas mileage
 

I'd have to first ask if you have run the 670 or if it is still in the box and you can return it.
With some careful jetting and some other tuning such as picking the right accelerator pump cams to help mileage you might get reasonable mileage with it.

Any carb has to be tuned to the engine it is on and the type of driving that the car or truck it is on is going to do. Many of us put up with a box stock carb that has little more than the idle speed set and the Idle mixture screws set for the highest vacuum reading and little else and don't get too carried away with trying to get the best performance and or mileage out of the carb.

Re: Carbruator for best gas mileage
 

The Holley came with the engine, so I can't take it back and I'm a long ways off before driving it. My buddy wants to buy the carb so I told him to buy me the Edelbrock, but he told me he didn't know if that is my best choice. He ask if there was anyway of finding out which carb would fit my needs the best, so I told him I would post on here to see what you guy's would recommend.

Re: Carbruator for best gas mileage
 

20 MPG on an AD series would be a stretch, the problem is that parachute in front of the hood. Add that to the wide tires and increased roll resistance you you have when running them and even with the best gearing and carb. you would be lucky to get 18. Then I had my '54 I ran a 350/700R4, 273 gear in the rear end and a 600 Holley. With 235/75/15 the best I could do was 18. Now I normally run 70 on the highway. If I would back to 65 it might help a little, but 2 MPH, no so sure.
Rob

Re: Carbruator for best gas mileage
 

This is a good question! I only know of the Edelbrock that's on my '59 with the 350, Th350 and 3:08, and then an Edelbrock on my '67 Mustang(289), c4 and stock 2:79). I get horrible gas mileage on both, but I've never actually checked it, I just know that I'm filling them up fairly often. I'll do better about actually checking next time.

What makes the Quadrajet some much more efficient Jackson? I googled it, looks like a neat carburetor.
dne'

Re: Carbruator for best gas mileage
 

Not encouraging, Denee, considering your '59 has the same set up as my '57 panel, but you have taller final gearing, which should give an advantage. I suspect mine has 3.7, or ?

Re: Carbruator for best gas mileage
 

Taller gearing does not automatically equate to better gas mileage. If your engine can't efficiently pull the gearing one of the two needs to change.

Re: Carbruator for best gas mileage
 

Mine is wound pretty tight at 65mph.

Re: Carbruator for best gas mileage
 

Denee;
I would also go with the Q-jet.
The Q-jet was the stock carb on most GM engines for a lot of years.
The Q-jet can be get from 15 to 20 mpg all depending on the trans n gears in rear end.
I have a 78 350 2bd that get 15 mpg.
The whole thing with 4bd carbs is as long as you keep your foot out of the back bds you can get fair mpg.
I just have never liked Holley for a street type engine.
Hope this will give you something more to think about.

Tim

Re: Carbruator for best gas mileage
 

So it looks like a Q-jet might work! What if I save my money and go with a TBI setup could that make any difference?

Thanks

Re: Carbruator for best gas mileage
 

;) It's not like I drive all over the place~ it's just a classic car/truck event vehicle and on special occasions. But it does concern me if that much gas is being used, is that playing havock on the rings and cylinders? I do know the edelbrock wasn't/isn't an expensive carburetor. I do like the looks of the Q-jet after Googling it, plus it being an original carb back in the day~ that's cool!:metal: Something to put on my list of wants! I'll never get to my TR6 for restoration! lol

Re: Carbruator for best gas mileage
 

Just how much money would you have to save up for a TBI? I'd like to see a pic of the setup, I'd never do it, but would like to learn more, and more, but I tend to forget it soon as I learn it! lol

Re: Carbruator for best gas mileage
 

The TBI setup is around $1100 from JEGS. Don't know if it's cheaper any where else.

Re: Carbruator for best gas mileage
 

Someone correct me if I'm wrong, but I think all Quadrajet carbs are spread bore with small primaries and large secondaries. If you are currently running an Edlebrock most likely you don't have the correct intake to use a QJ. There might be adapters available but I don't know for sure.

Re: Carbruator for best gas mileage
 

I just called JEGS and the TBI setup that is like a master kit which comes with everything is $2429 which is a lot of money and to improve gas mileage maybe 2 or 3 miles per gallon might not justify the cost. I ask his opinion on carbs and he said he like the Holley 600 with electric choke and vacuum secondary

Re: Carbruator for best gas mileage
 

I looked up the 600 cfm Holley on Summit and says not to use with overdrive transmission, so if I stuck with Holley it would be the 570 street avenger. I was also told that the Q-Jet has to be tuned about every 3-4 months. Don't know if that's true, but that's what I was told by a tech.

Re: Carbruator for best gas mileage
 

I've been hearing lots of good things about the new Demon carbs

Re: Carbruator for best gas mileage
 

Over the years I have ran everything from WCFB to 780 Holleys. Currently my chevelle (355/350th 3.08) has a Qjet and I have ran it two years without any problems or adjustments. tiny primaries so mileage is pretty good. Before that I had a 500cfm Holley @bbl on it. Not as good of mileage as the Qjet because the bores are larger. Got rid of it when the idle circuit starting acting up and I could not get it to run right. Before that I had a Edlebrock 600cfm Performer, but the idle circuit in it went fubar too. Not as good of mileage as the Qjet. On other SBCs I have had Holley carbs, but always seemed to be fiddling with them. Ok for race applications where it is full throttle. Around here you can get Qjets off of running engines for less than $50 when guys upgrade. Get the early ones before they added all the electronics. IF you want to speed the cash I have heard good things about the Edlebrock FI systems but have no personal experience.

Re: Carbruator for best gas mileage
 

Ricos54;

I have run the Q-jet on most every GM product. They are the best all around day after day driving carb that you can find,
Very easy to set up n adjust.
Q-jets ARE a spread bore carb.
That means they have small primaries(gas mileage) large secondaries(Performance).
They do make adapters for the Q-jets, I just dont really think they are very good.
Just find you a stock intake for the Q-jet.Q-jets hold the adjustments for a very long time once you have them adjusted to your way of driving.
When you go with the TBI system you lose some timing adjustment.
One other thing about fuel mileage with the Q-jet ,is that you can hook up to a ported vac outlet on the carb n get much better performance from the dist n carb..

Hope this helps you some more.
Good thought from (Russell n orrieG)

Tim

Re: Carbruator for best gas mileage
 

Maybe I'd just better look around for a nicer air cleaner! This is a good thread and I'm sure many folks wonder about the question of a carburetor;)
dne'

http://img.photobucket.com/albums/v4...ps63d8e8b0.jpg

Re: Carbruator for best gas mileage
 

Holley made/makes a spreadbore replacement for the Qjet. A well tuned carb can rival EFI for mileage. The trick is tuning. ;)

Re: Carbruator for best gas mileage
 

we have had great success with the q-jets using the edelbrock SP2P manifold, It is a old intake but works from idle to 5500 rpm. this is where fuel mileage is made, also have your dist curved to match the rest of it..I run a q-jet now that has been sitting dry for over 5 years, put it on cranked it and no leaks...

Re: Carbruator for best gas mileage
 

Not to change to subject (Rico forgive me for asking questions on your thread) , but Just out of curiosity, what is the high rise intake for? It looks neat! If my husband can buy boat loads of bullets, I can buy nicer looking bolt on parts! lol

http://img.photobucket.com/albums/v4...ps5115f48a.jpg

Re: Carbruator for best gas mileage
 

I picked one up for 50 bucks and found the adapter (I think from Mr. Gasket) to bolt it up to my Edelbrock intake.

Re: Carbruator for best gas mileage
 

No problem, I'm pretty sure the taller the intake is are the volume of air is going into your engine it changes the way it's delivered. It helps for power and helps to suck down the gas more. It definitely won't help with gas mileage, it should make it worse.

Re: Carbruator for best gas mileage
 

What differential (ratio) are you running?

Re: Carbruator for best gas mileage
 

Dne' this should cover everything on intakes
http://www.enginelabs.com/engine-tec...or-dual-plane/

Re: Carbruator for best gas mileage
 

Thank you! I think I'm going to print that out!!!;)

Re: Carbruator for best gas mileage
 

If that question was for me I'm running 300 gears with a posi 9" Ford.

Re: Carbruator for best gas mileage
 

It was. What is the gear ratio for your differential? I use a Camaro differential with a 2.56 ratio (because I no longer care about what it will do in the quarter) which I figure will give me better mpg as well.

Re: Carbruator for best gas mileage
 

Yes, when I found out the 9" in the rear was 3.00 ratio I said perfect. Then when I put 20's all the way around that should make the it even taller. Not sure what the 20's will do with the 3.00. I was guessing it would move it around 2.90 ratio. I found a calculator on the net and I ran my setup and it said at 65 I will be running Round 1680 RPM's in overdrive.

Re: Carbruator for best gas mileage
 

Ricos54;

You need to also think aboutthis;
If your rpm is that low at 65 your not reallyget the performance that would give you better gas mileage.
I how have a 96 chevy pu with 4.3 V6 n 700r4 trans.
just around town it does good in high at 45mph n about 1600 rpm.
running at 75-80 mph I turning 2200 rpm, which is still good for cruseing,just when I pull a hill it dropss into 3rd at 75 n 3000 rpm.
Just something to think about.

Tim

Re: Carbruator for best gas mileage
 

Yes, my buddy mentioned that and I've come to the realization that I won't have it all, but since my truck came with those gears I figured I would try it to see how it does. I'm sure there will be a few ways to go if I need to change something. Like putting in a RV cam or changing the gears. I was trying to find a happy medium which also lead me to the Carbruator. I figured the Q-Jet was the option for the best gas mileage I just worried about having power to turn those big 20's. Without having enough power especially getting that truck moving will also be hard on my gas mileage.

Re: Carbruator for best gas mileage
 

Hey Rico, Jim here. Don't want to step on your thread, but wheel dia. has nothing to do with changing the rear end ratio. Tire size does. A 245/40/20 tire is 27.6" tall. A 305/45/17 tire is 27.8" tall and a 235/70/15 tire is 28" tall. All are almost the same, but you have 3 different wheel sizes. Depending on the tire you select for your wheel, will make a difference. Based on my limited knowledge of overdrive trans normal 3rd or drive is a 1/1 ratio and 4th or overdrive is a .7 to 1. So your 3:00 ratio is now changed to 2:10, then your tire could change this up or down depending on how tall. Based on a formula from Hot Rod mag. years ago. It said MPH is equal to RPM times tire dia. divided by 336 times gear ratio. So 1680 times 27.6" (20" tire above) equals 46,368 then 336 times 2:10 (final drive) equals 705.6 So 46,368 divided by 705.6 equals 65.7 MPH. Almost the same as the one you found on the net. Hope I didn't mess things up for you..Jim

Re: Carbruator for best gas mileage
 

You can always give your opinion Jim, lol. I want to here from anyone that has knowledge so I can make an educated guess on what to do. According to that same site I found my tire hight will be 28.5"

Re: Carbruator for best gas mileage
 

Ricos54:

Just something else to add to your gas mielage.

Back a few years ago I had this set up in a car.
1- 1973 chevy caprice(big boat)
2- 350 V8 2bld
3- 400 trans
4- 273 gears
5 - 235 70 15 tires
6 - At 60 mph I was turning 2100( would run all day at that speed)
7 - never had a problem on take off
8 - got around 20 mpg on the open road.

So just some more info for you to think on.
It can get very scary when you try to figure out how to get mpg n performance together.

Wish I still had that eng trans n rear end set up! !