Fuel consumption...no not a tree hugger, just FMI

[old guys rule]

Hey guys,

Just looking for some figures from your cars average fuel consumptions.
Mine drinks like an absolute boss, like there is a hole in the tank.
I drive a '69 Coronet R/T, 440 with 750 CFM Holley 4-barrel (4150), Edelbrock Performer RPM intake, cam unknown but looking at the piss poor vacuum readings i have it's a heavy one
727 tranny and a 4.10 8-3/4" rear axle.

As far as i came it runs about 8 MPG, is that a reasonable figure for my car?

Future plan is to change the rear ratio to 3.55, to increase a bit on cruising comfort and obviously will help a bit on the fuel consumption as well.

Not complaining in any way, but just want to know it runs about right.

 

[old guys rule]

I know this thread is old so I don't know if you'll even see it, but I just could'nt resist' I thought I was the only nut job who was looking to max a 440 B-body for mileage although in my case I am looking for max mileage as a goal from the start of the build. Also dropped comp ratio to 8.2:1 to burn 87 pump. (really curious about the fun of driving a wimpy 440, we'll see) Just like the challenge and would like to drive it as a second family vehicle rather than just to car meets. Also a plus when you have been on a fixed income for 25 yrs as I cringe at the thought of paying for premium gas. Have built a number of hot rods in my day but the gas prices back then was a moot point (hence Old Guys Rule). Ready for official old fartdom now as I hit 66 a few days ago and have little choice in the matter. The cam in this one is pretty much a passenger type as far as duration is concerned but with a modern profile. Extra lift plus 1.6:1 rockers with a 112 degree LCA is as wild as I went here. Edelbrock intake, modified holly 750 carb, dual exhaust with magnum manifolds, manual 4 speed O.D. tranny ( .71:1 4th) and 3.23:1 gears and 27" tires puts the motor at 2000 rpm ( now it's torque peak) at 70 mph. This gives a final gear ratio of 2.29:1. Am very curious as to mileage it will give, anyone care to prognosticate? I stopped when I was 15 when I met my now wife of 50 yrs. LOL! Planning to drive it from Jacksonville FL to Amarillo TX to see an old high school auto shop buddy and take a good measure of the highway mileage. I know, long boring post but max mileage is a universal madness with old age (bragging rights), so little left to brag about at this point in life. That's all for now ( enough already!). Will keep you posted, I know it's what you live for! Super Dave

 

[hangn0ut]

I will take a shot. 20 mpg. 18 city, 23 highway. And that 8.2-1 comp, perfect for supercharging.

 

[Wietse]

Sounds like a pretty tamed 440 you build, then again you build it for it's intend of use for yourself and not for someone else.
I am quite sure you will get a decent milage out of that with those specs.
As stated in my last post, i am on the edge of going EFI, being it mainly for it's reliability over the good old carb.
Just wondering if i can still use the original fuel pickup in the tank.

 

[hangn0ut]

Sounds like a pretty tamed 440 you build, then again you build it for it's intend of use for yourself and not for someone else.
I am quite sure you will get a decent milage out of that with those specs.
As stated in my last post, i am on the edge of going EFI, being it mainly for it's reliability over the good old carb.
Just wondering if i can still use the original fuel pickup in the tank.

The good old carb can be quite reliable. I put together a 430" hemi for my 64 plymouth. Small solid lifter cam and a holley 830 double pump. Had 1 fuel filter per bowl. That car went 20 plus years on the street with no problems. My dad used that car as his cruiser most of that time. Only popped the hood to show off.

 

[hangn0ut]

Car should run ok with stock pickup. How it does at wot might be a different story. Can enough fuel be drawn through that line becomes the question.

 

[Wietse]

I am not saying a carb is not reliable, i rebuild my carb before and even then i had some issues with it.
I will have to go for a new carb regardless, because i want to go with vacuum secondary and a choke.
Now, instead of going for a new carb, spend some more and go EFI.
Car will not run wot all the time, it's a cruiser but time will tell i guess if i go for EFI first.
Later to find out if i need to change fuel tank with a internal fuel pump.
Fuel pick up tube is 3/8" which is recommended by Holley to use for fuel supply, return is a 5/16" hose

 

[coloradodave]

Wietse; Go to the Summit site for the EFI unit you are looking at. Download the installation instructions to get an idea of what's involved. When I switched over to EFI I originally used a FiTech engine compartment mounted supply canister with a high pressure pump. Unfortunately, it was early in their production and I had problems. I then rode in a friends car that used a frame mounted electric fuel pump mounted back by the stock tank. I decided I couldn't live with the pump noise as I drive my car almost every day. My next move was to buy a custom tank with an intank pump, which is what is in the car now. In my estimation, it's the best , although the most expensive, solution.
I have been using EFI for over 2 years now, and, although I tuned carbureted race cars, race boats and street cars, and offered carb rebuild services for a speed shop for many years, I will never go back to them. The benefits of EFI are many, including fast cold/hot starting, instant drive away, self learning to parameters you can set, and similar mileage to a well tuned carburetor. BTW, having that little hand held device, and being able to alter the A/F ratio on the fly, as well as the timing, is icing on the cake...

 

[old guys rule]

I will take a shot. 20 mpg. 18 city, 23 highway. And that 8.2-1 comp, perfect for supercharging.

Don't think that a supercharger hasn't crossed my mind! Dave

 

[old guys rule]

Wietse; Go to the Summit site for the EFI unit you are looking at. Download the installation instructions to get an idea of what's involved. When I switched over to EFI I originally used a FiTech engine compartment mounted supply canister with a high pressure pump. Unfortunately, it was early in their production and I had problems. I then rode in a friends car that used a frame mounted electric fuel pump mounted back by the stock tank. I decided I couldn't live with the pump noise as I drive my car almost every day. My next move was to buy a custom tank with an intank pump, which is what is in the car now. In my estimation, it's the best , although the most expensive, solution.
I have been using EFI for over 2 years now, and, although I tuned carbureted race cars, race boats and street cars, and offered carb rebuild services for a speed shop for many years, I will never go back to them. The benefits of EFI are many, including fast cold/hot starting, instant drive away, self learning to parameters you can set, and similar mileage to a well tuned carburetor. BTW, having that little hand held device, and being able to alter the A/F ratio on the fly, as well as the timing, is icing on the cake...View attachment 715518

Often wondered if a quiet electric fuel pump exists. Would be good for hot running conditions here in Florida.

 

[old guys rule]

I will take a shot. 20 mpg. 18 city, 23 highway. And that 8.2-1 comp, perfect for supercharging.

Hope your right. I plan to have it tuned on a local chassis dyno. I was hoping for 16/19. Remember my Dad had a 69 olds delta 88.. 455 a/t with a quadrajet...19 hgwy

 

[coloradodave]

Often wondered if a quiet electric fuel pump exists. Would be good for hot running conditions here in Florida.

Quiet pumps exist for low pressure applications (carburetors) but not for EFI where the pressure is much higher. Mine requires 58 psi minimum...

 

[Wietse]

@coloradodave: You got a nice setup there!
I did download the instructions and watched the installation video of Holley their website and am quite aware what is involved.
My biggest concern is the fuel tank pick up will work to supply the pump, which will be installed near the tank.

 

[coloradodave]

@coloradodave: You got a nice setup there!
I did download the instructions and watched the installation video of Holley their website and am quite aware what is involved.
My biggest concern is the fuel tank pick up will work to supply the pump, which will be installed near the tank.

If the pick-up is 3/8" I would use it. I would recommend you insulate the pump mounts with some rubber padding to try and keep the noise down. Good luck...and thanks for the compliment.

 

[kowalski]

Quiet pumps exist for low pressure applications (carburetors) but not for EFI where the pressure is much higher. Mine requires 58 psi minimum...

Check out Aeromotive's Phantom in tank pump. It will handle either carb or efi.

 

[kowalski]

Hope your right. I plan to have it tuned on a local chassis dyno. I was hoping for 16/19. Remember my Dad had a 69 olds delta 88.. 455 a/t with a quadrajet...19 hgwy

A qjet, TQ, or Street Demon (TQ , evolved) would be way better for mileage than almost any Holley. Definately look into a cold air intake setup, also.

 

[Wietse]

Hey guys,

Been playing around a bit with my carb, i've been lowering the primary jets, coming down from 78 back to 70 size (holley sizes) to see if i can get the AFR readings to come a bit more lean during cruising.
(Size 70 is as it comes from the factory)
I got stuck at 11.0 @ 40-50mph it seems, using smaller jets does not change a thing.
Hoping to reach a 12.0 - 12.5 during cruising at mentioned speeds but it seems something else is stopping me.
I am not sure what else was done with this carb so there might be something modified on the air bleeds or so?
I've also played around with ignition timing, coming from 20 deg initial with 18 deg mech advance, all in @ 2500 rpm.
Set it to 12 deg initial, hooked up vacuum advance, maintained same mech advance but with no changes.
Pulled cyl #1 plug to find it black with deposits...no wonder.
Any thoughts if this has to do with air bleeds or so? It's a Holley 4150 750cfm 4-barrel with mech. secondary's, not the HP version so i cannot replace air bleeds or so.
As EFI is off the list for some time i wonder if i should buy a new carb...i feel like this one is played around with too much in the past.

 

[hangn0ut]

Its the air bleeds in the emulsion tubes that need enlarging. The upper ones as they activate at a lower rpm.

 

[hangn0ut]

Primary side. Does the afr remain the same from low to high rpm? If it gets richer as rpms rise, you need larger main air bleed. If it goes lean, you need smaller bleed. Emulsion bleeds effect parts of the curve. Like the mid range or lower rpm. Or just the top end. The main bleed becomes more effective as rpms rise. So you adjust based on high rpm afr. If rich at high rpm then enlarge the bleed and vice-versa.

 

[Wietse]

Thx for your explanation.
When driving around 30mph the AFR reading shows more lean, around 12.0.
So my main air bleeds require to be larger, i have never looked at these or so and to my understanding these are not replaceable on my carb.
Or do these require to be drilled larger? Guessing were talking 0.001" increments here...
These are the ones that can be seen from top of the carb right, next to the intakes when the air cleaner is removed?