New bb build fuel economy

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plymouth1937

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Thinking about building me a 400bb whid 440 crank,ending up whid 451 cui,the direction whid this build is fuel economi not performance,as this engine orignaly is a low comp engine im shooting for 9.5 ratio,any sugestions on cam pistones intake carb,this is a low budget build so cast crank cast pistons and so on,what heads are the most efficent,cast stock heads,valve angles,mild porting.....
 
Your "whid" would be "with" in English. If you're looking for fuel economy I would not be concerned with adding 51 more cubic inches.

Tom
 
I have a 440 in my Duster that gets around 16mpg (if I can resist the urge to floor it).
30 over forged pistons,
Shaved 452 iron heads,
11:1 compression, (minimum of 93 octane required)
Edlebrock performer rpm intake,
mild street/strip cam,
Schumacher headers/2.5” exhaust/cheap 16” summit mufflers that barely muffle,
Holley Sniper efi and ignition system,
T56 magnum with a .63:1 overdrive,
3.73 rear end gear.
I didn’t build this car for fuel economy, so I’m sure it could be improved significantly with some aluminum heads, and a cam with less overlap.
 
Craig Burriss said:
I have a 440 in my Duster that gets around 16mpg (if I can resist the urge to floor it).
30 over forged pistons,
Shaved 452 iron heads,
11:1 compression, (minimum of 93 octane required)
Edlebrock performer rpm intake,
mild street/strip cam,
Schumacher headers/2.5” exhaust/cheap 16” summit mufflers that barely muffle,
Holley Sniper efi and ignition system,
T56 magnum with a .63:1 overdrive,
3.73 rear end gear.
I didn’t build this car for fuel economy, so I’m sure it could be improved significantly with some aluminum heads, and a cam with less overlap.
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Ok thanks at last a useful answer,whats the specs on your cam
 
plymouth1937 said:
Thinking about building me a 400bb whid 440 crank,ending up whid 451 cui,the direction whid this build is fuel economi not performance,as this engine orignaly is a low comp engine im shooting for 9.5 ratio,any sugestions on cam pistones intake carb,this is a low budget build so cast crank cast pistons and so on,what heads are the most efficent,cast stock heads,valve angles,mild porting.....
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if you're set on using a cast crank you need to think about line boring the mains on the block to the 440 crank journals.
if you use a set of rods at 6.76" (440 rods) then you can use a pretty common 1.32" compression height piston, made by many places. SRP, 440 Source, Ross, Wiseco, Icon. none are cast pistons though.
I would build for quench and use a closed chamber head like a factory 915 casting, or 440source heads.
quench would mean, you put the flat top piston close to zero deck and use something like a .039" gasket thickness with a closed chamber head.
 
I am/was (thanks inflation! :BangHead:) building a mild 440 for my truck (details in my signature) for mostly towing duties so low-end torque and fuel economy are priorities. I went with unported Stealth heads but my machinist strongly recommended a good valve job as the factory one is mediocre at best and a good valve job can really improve low-lift flow and velocity. Pistons are Icon forged pieces that will put the compression right around 9:1 (depending on final deck clearance and head gasket choice of course) so I can run regular gas and not have too much heat buildup when towing. For a cam I'm planning on getting a custom grind solid flat tappet (more just personal preference, don't trust hydraulic FT stuff much anymore but don't want to spend the $$$$ for a roller cam conversion) from Racer Brown with very mild specs, last he told me was something in the .430" lift range and 210-220* duration at .050" lift. For intake I'm using an Edelbrock RPM, actually the Mopar Performance copy I bought last year when there were just a few left in stock and before this crazy inflation hit. Carb will be the 750 cfm Street Demon I'm currently running on my Duster which has incredible street manners and is one of the best carbs available for gas mileage. And finally Hedman long tube headers with 1-3/4" primaries.

Truck currently gets 10 MPG with the mostly-stock 360 which I attribute to the heavy full-floating Dana 60 rear axle, 727 trans, terrible aerodynamics and oversize 33" tires, truck itself also weighs 4400 lbs unloaded with me in it. I don't think a fresh warmed-over 440 with raised compression could do much worse than that as long as I can resist driving with a lead foot lol.

I know it's not a stroked low-deck B engine and it's not finished so I can't confirm the performance but I hope it helps!
 
If I were going max fuel efficiency I would be asking the same questions you are. with your target 9:5.1 I would look into a boosted application with fuel injection as well. I believe there are some benefits to this by cooling the charge with methanol injection systems. Yes you pay up front, but with the goal of using the 400 platform.......or......look around for a 5.2 or 5.9 that has a dry manifold already and work that unit. I have not done it personally, but look up some boosted threads on here and see what they are getting for power and efficiency.

my 2 Krona

EDIT: I know this isnt the hard core answers you are seeking ie which pistons, what kind of headwork.....but if fuel efficiency is the goal, big cubes, smallish cam and boosted is one of many ways to get the job done.
 
I don't care what language you speak, "fuel economy" and "big block" don't belong together. Ain't happenin.
 
I can show you old school 383 2bbl (well I can't SHOW them to you know LOL) that banged right up against the 17-19mpg door. This would have been in a "big whale" too, but likely 2xx something rear gear.

My old 70 440-6 RR used to do 13.8,and I was not all that careful. This, at the time, was a factory stock 440-6 long block, headers, 3.54, Dana, 4 speed with G60x15 rear tires. It had a 800 dp Holley and whatever the popular 180 Edelbrock intake was. Occasionally I could get it up into 13.9-14 but that was rare, and again, I just wasn't that careful. This was before the "double nickel" speed limit by the way
 
My buddy recently completed a 72 dart with a 451(sniper)/4l60E and 3.50 gears, says he's getting 18. That's hot rodding around town.

If that numbers accurate, that's impressive to me.
 
plymouth1937 said:
Thinking about building me a 400bb whid 440 crank,ending up whid 451 cui,the direction whid this build is fuel economi not performance,as this engine orignaly is a low comp engine im shooting for 9.5 ratio,any sugestions on cam pistones intake carb,this is a low budget build so cast crank cast pistons and so on,what heads are the most efficent,cast stock heads,valve angles,mild porting.....
Click to expand...


Building for pure economy and expect to save money your almost certainty wasting your time money. How much gas do spend a year and how much do you think you can realistically save bet it will cost 5-10 years or more of saving to build it to do so.
Beyond good tune free flowing exhaust etc.. It's hard the dramatically increase fuel mileage, my 5th Ave with nothing done help fuel mileage gets 16 mpg in town my Avenger with the billions they spent they increased mileage to 22 mpg not much gain. It takes a certain amount fuel to move car your not gonna get a crazy increase.


But building and with a decent balance of power and economy can be a worthwhile goal cause saving money wouldn't be the overall goal so it don't matter cost cause performance cost money. For me decent power 350-450 hp with around 15 mpg plus would my goal, I wouldn't neuter it too much for a couple mpg.
 
For pure mileage you basically want smallest displacement highest rear gear, good thing with BB you could build it to work well with highest gear and decent performance.
 
mygasser said:
i don't see why someone would choose a 400 (or any big block) if economy was important, it just makes no sense :BangHead:
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If going all out economy, then yes not best idea, but looking for a balance performance/economy build definitely BB good choice able to make more power idle to 5000 rpm work well with the highest of rear gear, get away with lower hwy cruise rpm, can use a low rpm stall etc... then a similar powered SB.
 
Plym,
How much are you willing to spend to get good economy?
For best economy, a low duration cam will be needed. So any of the factory heads would be suitable. Early 516 heads are closed chamber, will be very efficient with quench pistons, but might be hard to find.
I have milled Chrys heads 0.120", zero problems, to gain compression. You need to also mill the intake face for port/bolt alignment. The Edel Perf [ not the RPM ] will be ideally sized & use a TQ carb on it, you can get recon TQs from Summit & probably the sponsor, Woodruff carbs. Mate bought two Comp Series TQs from Woodruff, plus jetting kit, they were very good.
High compression [ for efficiency ] & short cams with pump petrol are a detonation challenge.
 
RustyRatRod said:
I don't care what language you speak, "fuel economy" and "big block" don't belong together. Ain't happenin.
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Uhh.....That depends on what you consider good fuel economy.
I got 15.1 in this car.....

01 Ginger.JPG


Doing 70 mph.....Of course that is with a 5 speed manual with overdrive and 3.55 gears. If I were to down jet the Demon 850 and slow down to 60-65, I could crack 16, maybe 16.5. That is actually decent in my opinion.
 
Low end torque engine, stock cam, and 2.94 rear gears. 1406 Edelbrock 600 cfm 4 bbl carb. The secondaries are there if you need the added push.

Just paid $5.09 a gallon here yesterday. That over $5 a gal makes you rethink lots of things.
 
Diesel is just shy of $10.00 Canadian a gallon. The cheep gas is just under $9.00 a gallon where we are. May have to get a gas miser. I’m looking for a part time job to supplement my pension. Kim
 
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