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Discussion Starter #1
I have a 92 GT 5 speed 308 geared stock engine does have smog deleted with PS and AC. Get 23 MPG I drive this Car 2000 miles a month its a DD. 1400 miles are going to work on the highway.

Engine has 165k miles on it so I want a new motor.
Found a good deal on a stock block 347 going to add my GT40 heads off my cobra they have, upgraded dual springs, 3 angle, undercut valves. Good for a .552 lift Max (Will have Cobra intake 280 cfms T-moss ported. 65mm TB from cobra. also 1 3/4 shorties, Stock original cat H pipe) May try 327 gears later for better MPG and maybe 273 if the 327 get worse.

Best I ever got Stock 91 GT cam with 1.72 rockers 327 gears 27 MPG. 5 speed

Looking for a cam to give me best MPG not HP. Car make 220hp now thinking it may make 300hp after I'm cool with that just look for best MPG.

My thoughts
My stock cobra cam
270/270 .479 lift w/1.7 (.282" lobe)

Cam thats in car 92 GT cam
But with 1.7 rockers not sure how the new math comes out. 276/266 .444 lift w/1.6 (.278" lobe)

Explorer 5.0
256 / 266 0.422 / 0.448 lift w/ 1.6 But again would be 1.7 rockers not sure the math.

Trickflow stage 1
275/279 .499"/.510" w/ 1.6 But again would be 1.7 rockers not sure the math.

What do y'all think for a off the shelf for best MPG NOT HP If I can get better than 23mpg that would be great
 

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The 347 is 15% bigger than the 302, so expect the baseline mpg to be 15% less.

Given more torque/hp at any rpm, the 3.27's that work great in the stock 302 car, might be too much(not needed for the 347). So don't go to the 3.27:1 gears unless acceleration is the goal, it will hurt fuel mileage with the 347.

The GT40 heads are rpm limiters, in the 347 the stock 5000ish rpm is about all they should get you. The rockers you should consider staying with pedestal type, for reliability. Stud rockers need more care and checking on way more than stock type rockers.

For fuel mileage, the best would be a custom cam made for the combination, which is always the case. To guess at a cam, I'd stick with either the OEM truck roller cam(Explorer), or the HO cam, with 1.7:1 rockers.

Since you will be R&Ring the engine and heads, consider a mild cut on the head decks, any gain of compression is more power, and efficiency. Custom cams can be designed to work with 9.5:1 compression, on regular gas. That would save gas, and likely more than the cost of changing pistons and a re-balance; that's my hint.
 

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Discussion Starter #4
tesla makes cars with good gas mileage
You got Jokes LOL

Don't be one sided. I have a go fast car now I want a HWY car its all in fun.
 

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The 347 is 15% bigger than the 302, so expect the baseline mpg to be 15% less.
On this ^^^^

I doubt the relationship is straight as claimed. I'd also say the guy behind the wheel could well make the 347 get better mpg's than the 302 as a result of his driving habits over the same roads and conditions. There is a lot more to mpg results than the engine size. I'd say that expecting it to "anything" compared to a 302 is setting yourself up for potential disappointment. That's like expecting that orange to taste like a golden delicious apple.

I think it's safe to assume that he knows or expects a 347 is not going to fuel economy like a 302 and is ok with that. The question then is how to maximize the 347 for the stated goal.

The HO cam is the most aggressive of the factory cams. The Explorer cam was designed to push those relatively heavy SUV's around and might work well in a lighter car with more displacement. Because your displacement is increasing the effective duration of any factory cam is going to be tamed. If it were me, I'd run the HO cam, Crane 7/16 stud conversion and Scorpion 1.82:1 roller rockers. The bolt-on stud conversion is good to hold up to 350 lbs per Crane Tech Support.

Since this will almost certainly make buckets of torque down low, I'd be looking at gears that allow turning around 1800 at 70 with 26ish inch tall tires.
 

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Discussion Starter #6
I'm guessing the specs are?
Explorer 5.0
0.422 / 0.448 lift (1.6 rockers) Will be running stock 1.7 rockers
256 / 266 advertised duration
 

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Discussion Starter #7
I will be running the 1.7s that came stock on my gt40 heads for sure.
 

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Discussion Starter #8
Going from 1.6 rocker to 1.7 rockers from what I have read will add +or- .030 lift?
 

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The Cobra cam (which is the same as the 5.0 T-bird/Cougar) is 270/270 advertised with 0.282 lobe lift on 115 LSA. With the 1.7's that's 0.479". It is supposed to deliver stronger mid range torque. Might be good for the combo.
 

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Discussion Starter #12
Right now I'm really thinking about staying with the Cobra intake it has a little more lift and aggressive then the stock and Explorer.

The Trickfow if my math is right will work but its maxing my springs out at .531"/ .542 with the 1.7 rockers my max is .552 and I'm thinking that extra lift may cost me some MPG also.
 

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Indy, do you have any experience messing around with lean burn cruise? I'm sure it varies from setup to setup, but what sort of mileage improvement do you think someone could see?

Str8ballar, you might try browsing the "Green Rodding" forum. Not a ton of activity there, but you might find some threads that will help.

If you're really trying to optimize your fuel mileage, don't limit yourself to thinking about just the drivetrain. Electric power steering, aero mods, etc etc... will also help.
 

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utilize lean burn cruise, using a tweecer or QH
Interesting, what FN's are involved in this? I cruise at around 15.4 A/F currently.

To the original poster why not just find a focus for a few grand. You'll get damn near double the mpg. And for what you're going to spend on modding the fox that you won't need to do, it'll pay for itself.
 

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Discussion Starter #16
Interesting, what FN's are involved in this? I cruise at around 15.4 A/F currently.

To the original poster why not just find a focus for a few grand. You'll get damn near double the mpg. And for what you're going to spend on modding the fox that you won't need to do, it'll pay for itself.
Nothing cool about driving a focus to work 700 miles each way and who wants to drive a focus. Its not really about the money. I just want to get decent MPG while driving the car I like riding in.

Thinking I may add Megasquirt. Dyno tune it and try and get the best MPG I can it would be nice to have back up parts for the cobra if I need to check for problems. As I said its not about the money. Right now I have to stop 3 times just for gas being I'm getting about 250 miles per tank. If that goes down to 200 miles I'll have to stop 4 times.
 

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Discussion Starter #17
Down the road I may get a wild hair and turbo or supercharge it also.
 

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Nothing cool about driving a focus to work 700 miles each way and who wants to drive a focus.
I drive a 2013 Focus 5 speed manual everyday to work. About 250 miles a week. It's super comfortable for the driver/passenger (not so much for the rear seat). It drives really nicely. On an 80/20 highway/back roads split I get around 33 mpg. It's peppy. An ST would be a hoot. Probably get almost as good mpg's.
 

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I drive a 2013 Focus 5 speed manual everyday to work. About 250 miles a week. It's super comfortable for the driver/passenger (not so much for the rear seat). It drives really nicely. On an 80/20 highway/back roads split I get around 33 mpg. It's peppy. An ST would be a hoot. Probably get almost as good mpg's.
I'm not hating on the Focus it just not a 92 GT not sure I know how to explain but I like having the oldest car at work and it has a antique tag. When I was going up all the cool cars had an antique tag. If it was the 90s model turbo Focus it would be a different story.
 

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I'm not hating on the Focus it just not a 92 GT not sure I know how to explain but I like having the oldest car at work and it has a antique tag. When I was going up all the cool cars had an antique tag. If it was the 90s model turbo Focus it would be a different story.
It's definitely not a 92 GT. LOL!!! It is totally a throw away car. When I'm done with it, it'll be ready for the junk yard.
 
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