BBC EFI gas mileage?
Burning Brakes
Joined: Mar 2005
Posts: 1,139
Likes: 0
From: Salina Kansas
My efi 383 would get 17 on the highway with the 4speed and 3.08 rearend (probably 420ish hp, Sportsman 2 heads). I bet it gets close to 19-20 with the 5 speed, .68 o/d but I never checked it.
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
I've heard of low 20s being kinda normal, on the highway. Of course if you lighten the car, make it more aerodynamic in some form, and use an overdrive and lower rear gears you can get that pretty easily.
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
My '69 427/435 gets a whopping 6 mpg...anything would be an improvement. Two things keep me from converting it...it's all numbers matching and correct, plus I don't believe anyone makes a fuel injection system for the rectangular port heads.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
My '69 427/435 gets a whopping 6 mpg...anything would be an improvement. Two things keep me from converting it...it's all numbers matching and correct, plus I don't believe anyone makes a fuel injection system for the rectangular port heads.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
My '69 427/435 gets a whopping 6 mpg...anything would be an improvement. Two things keep me from converting it...it's all numbers matching and correct, plus I don't believe anyone makes a fuel injection system for the rectangular port heads.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
I was going to change it to a 5-speed but a sudden hospital stay made me rethink where the dollars available were going to be spent.
what kind of gears are ya running? do you have an overdrive?
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Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
The car runs 4.11 gears and it has an L88 camshaft...it's power band is from 4400-7000 rpm's. To say the least it's a pretty cranky engine. While it naturally has plenty of torque, when you pass 4000 rpm's you really feel a kick in the pants as it begins breathing.
As I said...I was going to install a 5-speed but an unexpected stay in the hospital and the bills from that made me change those plans.
As I said...I was going to install a 5-speed but an unexpected stay in the hospital and the bills from that made me change those plans.
Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
The car runs 4.11 gears and it has an L88 camshaft...it's power band is from 4400-7000 rpm's. To say the least it's a pretty cranky engine. While it naturally has plenty of torque, when you pass 4000 rpm's you really feel a kick in the pants as it begins breathing.
As I said...I was going to install a 5-speed but an unexpected stay in the hospital and the bills from that made me change those plans.
As I said...I was going to install a 5-speed but an unexpected stay in the hospital and the bills from that made me change those plans.
I am feeling a little jealous right now!
p.s. With a 5spd. don't ya think ya might be lugging that engine a little too much?
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
My intent with a 5-speed was less improving the fuel economy as I doubt it would be a whole lot, though it would have helped...and it never would have paid for itself for as little as I drive it. I was more concerned about keeping the rpm's and engine wear down.
I had thought about a 6-speed, but that would have required cutting the trans tunnel. I'm not about to do that since it's all in great condition with the original block, heads, intake, carbs, etc. No point in hurting the value, but any changes I have made aren't something that can't be readily returned to original...like the stereo/CD player replacing the original AM/FM and the MSD 6A hidden behind the passenger side of the dash.
That engine has so much torque it really doesn't need 1st and 2nd gears. 3rd and 4th is all it needs except trying to start on a steep incline. I've named it "Stumpy" since I think it could pull tree stumps.
I had thought about a 6-speed, but that would have required cutting the trans tunnel. I'm not about to do that since it's all in great condition with the original block, heads, intake, carbs, etc. No point in hurting the value, but any changes I have made aren't something that can't be readily returned to original...like the stereo/CD player replacing the original AM/FM and the MSD 6A hidden behind the passenger side of the dash.
That engine has so much torque it really doesn't need 1st and 2nd gears. 3rd and 4th is all it needs except trying to start on a steep incline. I've named it "Stumpy" since I think it could pull tree stumps.
Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
My intent with a 5-speed was less improving the fuel economy as I doubt it would be a whole lot, though it would have helped...and it never would have paid for itself for as little as I drive it. I was more concerned about keeping the rpm's and engine wear down.
I had thought about a 6-speed, but that would have required cutting the trans tunnel. I'm not about to do that since it's all in great condition with the original block, heads, intake, carbs, etc. No point in hurting the value, but any changes I have made aren't something that can't be readily returned to original...like the stereo/CD player replacing the original AM/FM and the MSD 6A hidden behind the passenger side of the dash.
That engine has so much torque it really doesn't need 1st and 2nd gears. 3rd and 4th is all it needs except trying to start on a steep incline. I've named it "Stumpy" since I think it could pull tree stumps.
I had thought about a 6-speed, but that would have required cutting the trans tunnel. I'm not about to do that since it's all in great condition with the original block, heads, intake, carbs, etc. No point in hurting the value, but any changes I have made aren't something that can't be readily returned to original...like the stereo/CD player replacing the original AM/FM and the MSD 6A hidden behind the passenger side of the dash.
That engine has so much torque it really doesn't need 1st and 2nd gears. 3rd and 4th is all it needs except trying to start on a steep incline. I've named it "Stumpy" since I think it could pull tree stumps.
