Hey guys, I've spent alot of time going thru some of the old threads, but didn't feel like they quite answered some of my questions. So here we go
(probably) again.
I have a 66 F250 with a tired and leaky engine and trans. Engine is supposed to be a 352, it appears to be. The trans, based on your input is probably a Cruise O Matic. My wants are about 300-325 HP, and possibly a fuel injected fuel system. Is it possible to achieve those goals with what I have or should I go with a newer 351W, which seems to be very easy parts and aftermarket accessory wise. Will the Cruise O Matic handle the higher horsepower or should i go with a C6?. Is there a later fuel injected engine that would swap well? This is a work truck that will eventually become my daily driver. I am interested in Gas Mileage, though Im not looking for miracles. Im not sure what kind of gears are in the rear pumpkin or how to find that out. Do I have to take the rear end apart to determine that. I dont have a tack on the truck, so that makes it harder for me to figure speed at rpm. I know these are alot of questions, I would greatly appreciate any help.

 

Hi tilerocket,

Hopefully, someone can help better with the 352/351 engine and trans questions, but when it comes to
mileage...it's going to be tough to improve on much. I have a 66 F250 with a 302/C4 and headers, and it gets
around 15mpg and really works well, even for towing. The gearing in your rear end can vary a lot...it
could be anywhere from 3:73 to a 4:56. It'll have a Dana 60 in it, and there should be a little ID tag under one
of the diff. cover bolts. I swapped out my 4:56 with a 3:73 for better road gearing, saved me some on gas
and helped the speed/rpm. Swapping the gearing is a little tougher in them than the 9" in the 100's. I opted for an
entire Diff swap.

 

as far as engines and transmissions, newer=cheaper.
you can easily get 300hp with an FE, but they're not cheap to rebuild. there are no fuel-injected parts available for it, although i imagine some people have done it the hard way.

they are good engines, though.

don't put any money into the COM. they're next-to-impossible to find parts for. the C6 was made up into the 90's.

i can't speak specifically to what would be needed to put a 351w in the place of the 352, but you can probably assume you'll need to buy or fabricate engine mounts.

keep your eyes open- the bellhousing bolt patterns change a LOT. for instance, your COM tranny won't bolt up to the 351w. whichever way you go, make sure to get parts that will bolt up.

 

Trocket, The 352 C-O-M combo should be correct for 66. The rear gear ratio is likely 3.25 or 3.00 unless special order.

I would look for a 390 or 428 if you want to stay with the FE and make some big power. There are some pricey aftermarket FI systems available.

A friend of mine in Raleigh has a hodrod 4.6 from a Lincoln with matching tranny. The truck has plenty power and he can get 23 mpg with it.

These ol FEs can make some awesome power, but are a thirsty breed. Combine that with the areo design and MPGs are hard to come by.

I tell peeps, have fun with your ol truck, get an Escort, Focus or whatever for the daily driver. Save some money, ride in comfort with the windows up.



John

 

His truck was only avail with a 4:10 or 4:56 in 1966. Most common in your truck is axle code 24 which is 4:10 open

 

351W are dogs with poor fuel mileage. A biggie is how much $ you have to spend. a EFI 460 with a 4spd Auto would be a great swap. Not sure where you are located but have a good one complete sitting in my back yard. Guy who moved from here just left it behind.

 

Hmmm, I let the 250 slip past me. 66 250s only came with 4.10 or 4.56 wow I learn something new.




John

 

The 3:73 I put in my 66 250 was from a 1971 Camper Special...the CS's usually
had better road gearing...had wider brake drums too.

 

Nothing wrong with an FE motor. They are light, produce great torque, and are pretty easy to work on. That being said, you have a few options. Personally I would dump the 352, and look for a 390/C6 combo from a newer truck. They are pretty easy to find. This will get you more power and fuel mileage wont change much and will bolt in, only probably needing the driveshaft length changed. Parts are the real issue with the FE motors, as they are more expensive. At a minimum I would change the intake, cam, 4bbl carb, and headers. Will probably net you about 50 horse depending on the tuning, and gas mileage wont be too bad. However, if you want to make alot of HP, its going to cost you with a FE.

Another option is going to a 460/C6 which are also plentiful. Parts are cheaper than the FE motors. Once again, intake, cam, 4bbl carb, and headers to make decent power. These are not a direct bolt in. You will need to change engine perches and will need to modify driveshaft length. The 460 is a good motor to make alot of power with down the road if you decide to do a bunch of work on it.

Nothing wrong with a 351W. Only real issue I see is getting a strong enough tranny for a big truck. C4s are the most common tranny behind that motor. There are some C6s with SBF bolt patterns if you can find one. The motor will make the necessary power with intake, cam, 4bbl carb, and headers, however, will never have the brute strength of the BBF (both 385 & FE). You may or may not need to change the engine perches. I ran a 302 in my '65 on the stock perches, and I started with a 352. You will also need to modify the driveshaft.

It will handle a mildly warmed over FE Im sure. 300-325 hp isnt too bad as long as your nice to it. However, as others have pointed out, parts, parts, parts. A C6 is a better option.

Yes. But this comes with its own issues. You could swap in an EFI engine from any late model truck, but you have to bring all the wiring, setup, blah blah blah, with the motor. If your going to EFI setup to try and gain lots of MPG, your doing it wrong. Realistically you might see a 2-3 MPG gain over a properly tuned engine with well setup carb on it.

Expect 15 MPG at best. I got around 17-18 with a 302 and 4 speed in my '65 at one point. You will see about 12-14 with a bigger more powerful motor.

Im assuming you have a Dana 60. Just pull the rear cover and count the teeth on the ring and pinion. Compare against various charts on the interwebs. I would strongly suggest a set of 3.55 gears for gas mileage reasons and if you are above 300HP and making good torque, you will have no issues.

Personally for ease I would go with either the 460 or 390 with a C6 depending on what you can find and what you long term goals are.

jowilker/John always says, find a donor truck from the 70s that has all the stuff on it that you want, and start swapping. Its a good method if you can get one. That may you have all the parts to do disc brake swap, power steering, engine perches, etc.

 

CGB- that was a *great* post.
i agree completely.

 

You can also calculate your ratio by counting the number of turns the drive shaft makes in relation to the revolution on the tire. Just jack it up, mark the tire and mark the drive shaft and keep track of how many times the drive shaft rotates in one revolution of the tire. 4 1/2 turns would be 4:55 to 1, etc. It's best to rotate the tire 10 times and then you would have 45.5 turns of the drive shaft for the same 4:55 ratio, less "close guessing" that way. If it is limited slip jack up both sides, if it is open keep one tire on the ground. You can tell if is limited or open by jacking up both sides and rotating a tire, if they both turn the same direction it is limited slip and if they turn opposite directions it is open. Hope this helps.

Matt

 

A good choice if you are only looking for 300 to 325 horse power and retain decent fuel efficiency is a FE 300 6 cylinder with some mild modifications. Back it up with a c6 and you will have a unique strong truck with better gas mileage than all those 302s out there. As a side benefit, you will produce more torque. Ford didn't equip this engine in the F250 for all those years for nothing.

 

Never seen an FE described as "light".....lol

 

I was smiling at that too, unless of course you think 700 lbs is light.

 

Go with a 390 or 428 if ya can find one. 428s are getting pretty scarce and if ya find one, you will pay. You can do a LOT with a 390. Optons are plenty. With all the cams, cranks, pistons, heads, intake and fuel system combinations, you can have pretty much any amount of HP you want. 390s are plenty.

Try a 390 with a decent cam, intake and carbration. They also make throttle body injection systems (big $$$$ though) for just about any applicaton. Go with a C6 and a 3.00 or even a 2.75 9". Since you get better fuel mileage with the taller gears, you will also get slower take off speeds. Your C6 will do a good job to compensate for this, BUT switching your torque converter out for one with a higher stall speed of 2600 - 2800 will do you a world of improvement. Depending on your cam size, you may need to raise the stall speed anyway. This combo of tall gears and higher stall speed converter, will allow you to burn that rubber all the way down the street as well as give you decent fuel mileage on the highway.

NOTE 1: The larger the came duration you have, the less vacuum you will have during 'throttle' which will greatly effect any stored vacuum needed to safely operate you power brakes. Remember, vacuum is stored in the booster for this purpose. They do make extra vacuum tanks that can be added to the existing booster you have. These tanks come in both stand (non-electric) and electric types. Standard vacuum pods can be found on many old cars at your local yards. Either in the engine compartments or under the left front fender, just to the rear of the tire.

NOTE 2: Your FEs can take a pretty high lift cam, as well as a hefty duration but will require you to also upgrade your intake and carbration. With the already hefty size of the stock cast iron exhaust, I would opt for larger exhaust 'pipes'. Headers, unless you plan on turning some very high RPMs for a sustained length of time, are not really needed. They do sound cool, if thats what you are trying to achieve. Headers only start working at your higher RPMs. With headers, you will also loose some low end torque. Of course, all depends on what size cam you decide to install. Just about everything functions around that cam size.

There are many FE building books out there and can be very helpful. Do your homework first.
Fritz