352 versus 390 fuel economy
 

First of all, as I have said before I know this is not the "engine" forum, but it is the BEST forum and I never get the same quality of responses from the others so...

I took the 352 block from my daughter's 66 F100 Ranger to our local engine shop to be bored out. While there, the shop owner was busting on Fords in general and on the 352 specifically. He "claimed" that a 390 was superior in every way to the 352 (including fuel economy) and suggests I should get a 390 crank, rods and pistons while I have it apart.

Can anyone verify or debunk that statement? I can understand the 390 having better power and torque, but I am skeptical of his claim that it gets better mileage. He said the "poor geometry" of the 352 is the reason. That explanation is a little too vague for me. I have a 352 in my 68' F250 and I find it perfectly reliable and a good puller. In short I like it, but it does leave something to be desired in the MPG department; no surprise there.

I appreciate any and all input, but I am looking for fact not opinion. Thanks.

The guy is an idiot, from the 352 up to the 428 use the same block, just different bore and stroke and some of the oiling is different. As far as gas mileage, my 390 will get between 4 and 10 mpg depending on how heavy your foot is. If you want mpg look into an overdrive automatic trans and do a stock to mild build on the motor, headers and exhaust helps but you also need the right size carb and have it tuned.

As long as you're boring the engine out, now is the time to convert it to a 390. All that's needed is the 390 pistons, crankshaft and rods.

The mileage will not be any better with a 390. In fact it will prolly be about the same.

Expect no more than 8-12 city. On the highway 14-18 is the norm if you drive 55-65.

In 1981, I did exactly this with my 1965 F100, added a 1966 Galaxie 4V manifold and carb.

If you have a 352 in your 1968, it's not original to the truck, it would have come with a 360 or 390. The last year for the 352 was 1967.

The engine code is the 4th digit of the VIN: 1968 F100/350: A = 240 I-6 / B = 300 I-6 / H = 390 2V / Y = 360 2V.

:confused: Ford confusion: Y was used in 1966/67 for the 352; 1968/76 for the 360. D was used in 1965 for the 352.

I believe the bore difference is only .05 but has a much larger stroke.

Typically when a machine shop starts talking geometry that is in reference the the valves tips and rocker arm contact patch in regards to how the lift of the cam effects it. You end up changing pushrod lengths to ensure the contact patch is in the middle of the valve tip to prevent premature valve guide wear. Funny thing is that the heads interchange with one another with a few here and there that don't. Ask him if he meant to say "I use words that you most likely don't understand that implies to you that I do to make you build what I want because I am arrogant and suffer from a small (insert your word here)."

NumberDummy,
You are correct (as usual), man I get tired of typing that:) The 68' does have a 360 at least according to the air cleaner housing.

Everyone else, thank you for the input. I understand that neither engine is an MPG champ. My logic was this: The 390 has an extra 38 cubic inches sucking the same fuel and air mixture every revolution. Even at idle, it seems to me, the 390 has to be taking more fuel. But maybe there is something I am missing.

Since I am building this truck for my daughter (who doesn't care about tire screeching or quick starts at the green light) any fuel saving is more important than improved performance (HP and Q). I wish it had an I-6 240 or 300 CID.

For Air Harley,
Yes, he is one of those, but he's close and has all the right equipment to machine engines. A good machinist does not necessarily equal a rocket scientist; that's for sure:)

If you think the 240 or 300 will give better MPG, think again.

The 240 was a slug, the early engines burned oil like a diesel.

Around town, the MPG will be no different than with a 352, 360, or a 390.

On the highway with an I-6, you might ... might get 1 or 2 MPG extra.

These trucks have the aerodynamics of a brick. When these old rolling piles of misery were new, a gallon of 105 octane premium was around 35 cents a gallon, regular between 20-25 cents a gallon.

Back then, no one gave a hoot about gas mileage.

The 390 heads have larger ports than the 352, I compared the two when my 352 was getting rebuilt.

It will cost you a bit more when you add in the cost of another crank/rods/pistons/heads/intake/carb if you convert to a 390-4v. That's just something to consider.

I put an RV cam in my 352 when it was rebuilt and kept the 2-barrel and it runs great with plenty of power.

Uh huh, so what's this?

C4AZ6049C .. Cylinder Head / Fits: 1964/67 352/390/410 & some 428's / Use without smog pump.

Besides using the same heads, the 352/390 used the same valves, pushrods, valve springs, the whole valve train is exactly the same.

In 1968, Ford replaced C4AZ6049C with C8AZ6049M. These heads are the same as 1968/71 390/428 (except 428 P/C & HiPo).

I dunno what heads your 352 had, but I know mine were the originals since I bought the truck new.

Some much has been swapped around, who know what heads an FE engine may have?

The C8AZ heads were used by Ford authorized engine rebuilders, so these same heads could be found on all FE engines except 352 HiPo's (1960 only), 1961/63 390 HiPo's, 406's & 427's.

I love these fuel mileage threads...I have a nice and tough as nails 65 3/4 ton with the 352...single digit fuel mileage last I checked...I didnt buy it for fuel mileage...I bought it for hauling ability and the trucks particular sentiment...fuel mileage wasnt a consideration...If one wants a truck with decent fuel economy...get a later model Ranger...of which I have one thats been very faithful to me and is still moving along 275K later...or a 70's Courier...the Rangers predecesor...
As far as the FE engine differences...another thing I get a good chuckle out of when people compare the 390 to the 352...as Bill said, virtually identical...only the rotating assy is different...
Anyway, keep the 352 a 352...nothing gained by punching it out except a lighter wallet....which to me is the best reason to keep it stock...keep the wallet as heavy as possible :-)



- cs65

Or, you could get a 4 banger con-Fusion like I did.

Fold the rear seats down, a 4' x 8' sheet of plywood fits just fine, as long as you cut it in half.

When I cleaned out Pasadena Ford, I had 60 bound parts catalogs in binders, two microfiche viewers, another dozen catalogs without binders, some binders only, 500 microfiche slides and a lotta other jazz in this car, and still had room for one Basset Hound, and a stick of gum.

She, who must be obeyed, recently drove the pile 340 miles RT from LA LA Land to San Diego, got 35 MPG.

I love these fuel mileage threads, too. I especially love them when people say they spent mega bucks and now they've gained (a paltry) 2 MPG. :-missingt

I wonder if they thought...beforehand...how much gasoline could be bought with their mega bucks?

You can spend a grand, you can spend ten grand attempting to improve MPG, but all you are doing is throwing your money away.

When you have a truck shaped like a brick outhouse, the gain in MPG will not be worth the money spent...not to mention all the time and labor involved.

Maybe the heads are just ported differently on the 390. The engine builder showed me the difference in port sizes between the two and the 390 ports were significantly larger. The heads were Ford heads, not aftermarket.:confused:

I never said one word about the heads being aftermarket.

How many different FE heads were used from 1958 thru 1976? Dozens!

Which heads does your truck have? I haven't a clue, I do know what was there as original, but...

After 40 + years have passed by, who knows which heads are on the engine now?

And, who knows after 40 + years have passed by, if heads were ported and polished sometime in the past?

Ironically

Majority of 66 F100 352 had head with casting # C6AE R
Intake port aprox 2.25 inch tall



Majority of 68-70 F100 360 & 390 had head with casting # C8AE H
Intake port aprox 1.9 inch tall

Width of ports are the same.

66 & older, the average "typical" FE heads had the 2.25 inch tall ports so a lot of 390s came with the taller port, just not in trucks.