Gas mileage

[ender2664]

I have never run a carb'd motor before so please help me out here.
So gas mileage...is there a big difference between a 302, 351 and 383? Does anyone know about what kind of gas mileage I should expect from a small block?

[Detroit Bill]

Not good that's not the point. I'd imagine a range of 8 to 15 depending on the build, how you drive. Where you drive. Rear end ratio.

[mikeinatlanta]

Based on the information you provided, somewhere between 3 and 25.

[ender2664]

Originally Posted by mikeinatlanta

Based on the information you provided, somewhere between 3 and 25.

What information can i give you to get a better estimate. It is probably going to have 3.5 gears and a 5 spd manual.

[mikeinatlanta]

The block is irrelevant. All aspects of the motor and driveline will have a dramatic effect on mileage, as will your driving habits. Quite frankly, if gas mileage is a concern, you are looking at the wrong vehicle.

[ender2664]

Gas mileage is a concern if the difference in gas mileage between a 289 and 383, making similar power, is 50%...
My daily driver gets good enough gas mileage, but i don't want to be getting 7mpg as it would make the driving experience less fun for me.

[mikeinatlanta]

I don't mean to be rude, but your question is not answerable. Would you feel better if someone just threw you some BS numbers?

[Detroit Bill]

I can do that. 12.

[Detroit Bill]

This may fall into the "if you have to ask it is not for you" category.

[kevins2]

I've been very conservative with my cars over the years regarding gas mileage and was initially concerned about the Cobra mileage when I was where you are now. I can honestly tell you that the car is so much fun to drive that, even with my conservative nature, I really don't care about gas mileage.

On another topic, you have a number of questions floating around that have been answered multiple times in existing threads (including the gas mileage question, tires, HP, roller cams and aluminum heads). If you start seeing sarcastic or less than helpful responses, you might consider using the search function because some of what may start coming your way will be for that reason - the answers are out there many times already. Just trying to help... There is a wealth of information on this forum. Enjoy.

[Ace23]

Originally Posted by ender2664

I have never run a carb'd motor before so please help me out here.
So gas mileage...is there a big difference between a 302, 351 and 383? Does anyone know about what kind of gas mileage I should expect from a small block?

I will be the first to tell you I don't own a cobra yet. From the discussion I've had with the local cobra club the take is 8-15mpg. All the cars in the club are 427 except for a fuel injected 302 and I believe a 396. I think if you are just cruising you could expect 11-12 mpg in the 427 cars and may 8-10 with spirited driving. If you drive 1000-1500 miles a year its not a big deal.....if you really spend some serious seat time maybe look into a Coyote. I've heard those can be 20mpg+. Obviously tires, transmission, gearing ect.... all play roles in this.

[mln385]

I have a 351 stroked to 427cu and a 770cfm Carb, I get roughly 12MPG hwy. in 5th gear with 3:46 rear gears if I have my foot in it I'd be lucky to get 8mpg.

As has been said if MPG is a concern you in the wrong car, however you can minimize if you go fuel injected you will increase the Mpg. Also remember HP will cut into the MPG.

[cycleguy55]

I haven't done the calculations on it, but the previous owner told me the best he ever got was 15 MPG. I'm pretty sure that was downhill with a tail wind...

[GregAgrest]

I have a 351 stroked to 408. I drive conservatively but get on it once in a while. I get about 12.5 per gal. As stated before, it's really how you drive it. Heavy foot equals low mileage.

[wkooiman]

Here are some numbers.

My 2001 Viper GTS ACR with a 488" V-10 gets 20mpg on the highway.

My 1972 Pantera got 20mpg with a stock 351C + a Torker and Holley.

The Pantera dropped to 19mpg with a small solid cam and aluminum heads.

It dropped to 12mpg with Webers.

The Holley is going back on, and I hope to be in the 18-20mpg range again. I'm not doing the swap for MPG, but rather to make it look more like a Pantera and less like a race car.

My 428 Contemporary gets maybe 13-15mpg. I'm not really sure. I drive it. I gas it. I drive it again. Engine seems to be stock, with a top loader and 3.54 gears.

The engine size doesn't matter as much getting the rpms down (5-speed), and having the carb and timing adjusted properly. That's how the V-10 Viper does 20mpg. 6th gear is a 0.50 overdrive, and the rear end is 3.08:1. 70mph is something like 2500 rpm.

But like everyone said, once you get the car, you won't worry about gas mileage. It's not like you're going to drive it every day to work.

[Dwight]

Mike Hodge 408W 530 hp 3:55 gear 26" tires 5 speed, drives easy,13 mpg

I have a fuel injected 302 / 354 ci 500 hp 3:55 gears 26" tires 5 speed, leave the red light fast most of the time. Not smoking the tire but quick, I like the feel of acceleration. I get 20-22 mpg

But like it has been stated, a ton of fun per mile per gallon

gas mileage is the way you drive plus the gearing (tires size and air pressure plays into the equation)
Motor tune, we changed the jets in Hodges carb and he went from 6.7 to over 13 mpg.
air cleaner
exhaust system
type of gas your burn, ethanol or non ethanol gas
do you drive a couple of blocks and stop or is all your driving on the hiway?

Jeff has a 302 carb'ed stockist motor with 3;54 gears, get 25 to 29 miles per gallon on the hiway. Very easy driving.

It's more than the motor


Dwight

[1795]

To get the best gas mileage and performance you want to make sure that you match the power curve of your cam to the transmission and rear end gearing. If you go for an overdrive transmission and then match it to a a high speed reared (say, 3.31 for example), you may spend all of your time in lower gears if the power band of the engine is in the 3,000-5,000 range. Take your time and think things through. Use the search engine as others have suggested and wear tall rubber boots as you sift your way through the BS to find the kernels of knowledge (corn) floating with the turds

[WardL]

I consider MPG an interesting factor in the selection of an engine. I have a Roush 427 SB with a 750 double pumper in my SPF. Racing around I get 9. (Sitting in traffic I get zero....) Cruising along on the freeway I can get 15-17. It really is true that you just don't put many miles on the Cobra to worry much about MPG. Not once have I been thinking about gas mileage when my foot is in it. You just don't think about anything except maybe the exhilaration and sound of flying..... get the engine that gives you the performance you want. I think I might go with the modern day engine (Coyote) just so it doesn't stink as much....

[SPO 3098]

My information is based off of my Keith Craft built engine in my Mk III Cobra 427. It has an aggressive cam with a 780 cfm carb on top through a TREMEC 5-speed with a 3.42 final drive. As mentioned by several before me; a number of factors will effect gas mileage. With this set-up you will see 12 - 16 MPG, but can be as low as 8 MPG. I believe the 5-speed transmission helps a little if not just to keep the engine from turning so many RPMs at highway speed. I hope this helps with your decision process.