383 build for efficiency

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qkcuda

qkcuda

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I went and looked at a project car with an original 383. The car was a dud but it got me thinking. As opposed to a magnum or late model hemi swap, could you build a stock bore and stroke 383 for efficiency that would get decent mileage and power, and be reliable for long trips? The goal would be a cruiser that could run A/C and maybe an overdrive. How would you build it? I am thinking Edelbrock or 440 Source heads, FiTech fuel injection, Performer RPM intake, Schumacher headers, maybe a small hydraulic roller cam. Any thoughts?
 
Why a TBI EFI? From what I have been reading TPI has many advantages over a "self learning TBI".
OD...assuming an auto? A lock up convertor will drop your rpm a bit...more importantly will eliminate all efficiency killing slippage at speed.
Have always wondered how a stroked 400, say a 451 would run if it were treated to some of the modern day stuff. Similar to what you are talking about...a hydraulic roller designed for EFI, perhaps use some of the modern coating technology.
I do know of someone that had a 572" HEMI. Was over 700hp. No OD, FAST EFI...got close to 14mpg on the freeway. Hmmm...
 
qkcuda said:
I went and looked at a project car with an original 383. The car was a dud but it got me thinking. As opposed to a magnum or late model hemi swap, could you build a stock bore and stroke 383 for efficiency that would get decent mileage and power, and be reliable for long trips? The goal would be a cruiser that could run A/C and maybe an overdrive. How would you build it? I am thinking Edelbrock or 440 Source heads, FiTech fuel injection, Performer RPM intake, Schumacher headers, maybe a small hydraulic roller cam. Any thoughts?
Click to expand...

Honestly, you probably wouldnt need to go aftermarket on the heads. A good intake like the Holely Street Dominator (which is amazing on the B series engines), a good cam, the FI, headers all that you mention would be good. If you wanna gain even more, you could go water meth with the money you saved from the heads and even a propane conversion. all that would help a ton in MPG over just the heads.
 
Just thinking by the time you invest in valves springs etc. for iron heads you could almost buy a set of 440 Source heads, and the closed chambers would be better for compression and quench. That said I bowl ported a set of 452's for my 400 which flowed as well as Edelbrocks up to 450 lift where they stalled. Those would have worked well on this type of build.
 
440 source or sidewinders, rpm or street dominator, and the fitech is pretty cool stuff. A hydraulic roller would be a good fit.

For even more efficiency/ mileage lightweight rotating assembly I would think would help as well, top notch machine work is a plus too!
 
Anybody want to chime in with cam recommendations? I'm thinking low overlap, but not sure how much duration you would want.
 
If I wanted efficiency from a 383, I would just blueprint up a 383 HP Road Runner engine. Done.
 
for best mileage you need hi compression.
reasonably hi lift cam with short duration...and must match your drivetrain
as well as your engine.
..your maximum lo speed torque must be your cruise rpm,many have installed
an od transmission and had their mileage go down because they were cruising
at an inefficient rpm for their motor.
an o2 sensor and wideband a/f computer can really pay off here
correct gears,small primary venturi,light weight,lock up or lo stall converter.
very complicated subject!
 
As stated above, max efficiency is generally at peak torque (I've heard, but have no confirmation, that a 427 Cobra got its best mileage at 105mph...). I'd spend some time looking at dyno sheets...
 
It's not necessarily engine size that dictates fuel mileage. What I'm about to say is just generalized.

383 basically can get the similar mileage as anything other N/A is available for our A Bodies it's basically how much performance you willing to give up for mileage.

A 198 /6 is basically half the cid of a rebuild 383 so if you run a 383 at half the rpm at any given mph compared to the 198 /6 should get the similar mileage and performance for that matter.

Gearing and cam choices are gonna effect your mileage the most.

If your willing to go overdrive and custom roller cam with a wide lsa and short duration and maybe even high ratio rockers you could build best of both worlds with a good set of heads. Plus I'd stroke it out to 431 cid to be able to build a .9-1.1:1 hp per cid engine.

Just remember it's hard to recoup on mods for gas mileage sometimes.
 
What do you think of this hydraulic roller cam? Wide lobe center, good lift, low duration, good operating range.
Lunati 20230710
211/219 duration at .050
.507/.515 lift
112 lobe separation
1,400-5,400 operating range
 
Jim Lusk said:
As stated above, max efficiency is generally at peak torque (I've heard, but have no confirmation, that a 427 Cobra got its best mileage at 105mph...). I'd spend some time looking at dyno sheets...
Click to expand...

maximum lo speed torque
 
I don't understand how setting your cruise rpm at peak torque gives you maximum mileage. Sure that's the highest VE % but in a street engine that's usually around 3500 rpm. A engine turning half that rpm at cruise can't be burning more than an engine spinning twice the rpm (peak torque) and on top of that the engine spinning lower has less % VE so its ingesting less air and fuel even though it's way less efficient.
 
Maximum lo speed torque or most efficient
it's not maximum torque..that would be well beyond the point of diminishing returns.
like paddling a canoe..there is a point where you get the most speed with the least amount of work.
and if you paddle twice as hard you will not double your speed,but you will go some measure faster.
Everything mechanical has a sweet spot where you get the most bang for your buck.
 
I'm with 273 on this. Why would the rpm at which peak torque occurs, which is measured at wide open throttle , correlate with part throttle fuel efficiency? I believe it's just an old myth. A new Challenger 6.4 Hemi makes peak torque around 4200 rpm. Shift it out of overdrive into one of the lower gears so that you can drive at 4200 rpm at 70 mph and see what happens to your mpg.
 
ir3333 said:
Maximum lo speed torque or most efficient
it's not maximum torque..that would be well beyond the point of diminishing returns.
like paddling a canoe..there is a point where you get the most speed with the least amount of work.
and if you paddle twice as hard you will not double your speed,but you will go some measure faster.
Everything mechanical has a sweet spot where you get the most bang for your buck.
Click to expand...
What is this "maximum lo speed torque" you speak of? How does it differ from maximum torque?
 
o.k. suppose you make 360 ft.lbs @ 2400 rpm.
now you go to peak torque and make 400 ft. lbs. @ 4200 rpm.You have nearly doubled your rpm but you are only making 40 more ft. lbs torque and probably using 4 times as much gas to double your speed.You only need about 40 hp to cruise at 50 mph and that is about where the cam in this example makes the most power with least amount of gas.
 
Google Super duper MPG 273/318 experiment
Hot rod Dave did this over many months giving results with every change.
I think he ended up at nearly 30 mpg with his 318 test engine.A super read!
 
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