I am shopping for a replacement engine here: http://www.rebuilt-auto-engines.com/

Under Ford, they list both a 390 and a 391 engine...what is the difference?

Also.....under the 390, there are 3 different ones....one specified for cars, one specified with 4 "smog holes" and one "without smog." I assume I'd need the "without smog" one for a 1967 F-250? Is that correct?

 

seems to me, 391's were truck engines and had a longer crank snout. i think they had a diff. bore size. smog engines had thermator holes on the exhaust flanges of heads for cars in california. if you're smog exempt, dont bother with looking for smog equipment.

 

The 391 is a FT series engine and will not easily swap for a FE engine. Different crank snout as mentioned and different motor mount locations. I'm not sure about bell housing pattern, that might be the same.

 

Is there any way to tell if my current engine is 390 or 391? Just want to avoid any surprises in the process....

 

391 does have a forged crank with a bigger snout that can be machined to work in a 390.

 

The FTs were used primarily in the larger trucks, F-500 and up. There were some smaller FTs installed in the U-Haul trucks, and I don't see any orange paint in your gallery. LOL

Ok, so you don't want the 391, and you don't want the 4 smog holes. As for the car v.s. truck engine, the car engine should have a higher compression ratio...different pistons. Maybe some these hot-shots here can shed more light on the car/truck comparo.

 

car to pickup have different oil pan and oil pump most pickup are 2bbl and cars are 4bbl

 

Trucks ran 8 to1 or less compression, cars ran 9.5 to to 10.5 compression. Nowadays 10.5 is a premium fuel compression so most engine rebuilders rebuilt in the 9 to 9.5 to 1 compression.

 

It's a long block, right? You're using your old oil pan and pickup tube so car/truck won't matter from a mounting perspective. You will also be reusing your old intake, carb, valve covers, water pump, dizzy, etc, etc.

 

i have a ford 391 freshly rebuilt .030 brand new from a to z
dish piston fresh head all with the hd pump i have picture if you want
i can also take picture of the inside piston in the cylinder
this an industrial block that has seen very little activity
im asking 1600.00 for it

you may call me me at 514-815-4497
reason of sell im changing motor project for my galaxy
gate

 

I think he already bought an engine.

 

here is a link that will explain in detail the difference between the these blocks

Ford FT vs. FE - BumpWiki

the 391 crank is a very valuable part,,, but since it is not internally balanced
you cannot swap it with other part ( not mentioning the sizes )

but read this article ,, youll find out that in nascar racing they were often using the 391 crank to build some hot 396 cu that were often in front of richard petty

 

Fe vs FT seems to cause a lot of discussion everywhere, so here's my input:

The blocks are the same with one small but important variation; the hole in the block where the distributor shaft goes is of a different inside diameter, with the light duty and passenger cars being smaller, So, the truck distributor will not fit into the FE block. The light duty distrbutors will fit into the FT blocks but not have the side support needed and will cause the distributor gear to wear rapidly.
Also, the oil pump key/driveshaft is a larger hex on the FTs and require the larger FT oil pump.

The crankshafts, both iron and steel, are the same with the exception of the snout being of a larger diameter and if the crank is to be used in an FE the snout diameter must be reduced to the same dismeter as the FE's and a new keyway cut. The FTs are internally balanced to a lower rpm and must be rebalanced for higher rpm usage.

The rest is nearly all interchangable. The heads of most FTs and industrial engines have a dual manifold heat passage, small intake ports and valve rotators on the smallish valves. The pistons will usually have a dish or reduced piston pin to piston crown measurement to reduce compression.

Hopefully this is about all of the major differences. I'm sure that if I forgot something it will be cleared up by others here.

 

false
here it goes :
The Ford FE engine family consists of the following engines:

• 352
• 360
• 390
• 406
• 410 (Mercury)
• 427
• 428

...and were installed in cars and light-duty (LD) trucks.
The FT engine family consists of the following engines:

• 330MD (Medium Duty) - FE block with FT heads; pretty uncommon
• 330HD (Heavy Duty)
• 332
• 359
• 361
• 389
• 391 engines

...and were installed in 1964-1978 Louisville medium-duty (MD) trucks 2-ton and larger (F500-up). You could get a 391 in an F350 through fleet sales, though they're pretty rare. The FT's were an option in F350's and there was a heavy duty engine option on F250/F350 that Ford called a 361/391 but in reality it was an FE with FT heads.

FT engines have a single front mount that attaches to the steel timing cover This is a '69 (?) F-700 cabover.


The 330FT was standard in some 500 and 600 series trucks, and the 361FT was optional. F700-750-800 series are generally 391's (and are usually called a 391HD), though the 361FT was standard in some larger series trucks (700 and 800 maybe), and the 391 was optional. A 389 is pretty much the same thing under a 2V carb.
Most 330's, 361's and 389's came with a 2V Holley, and the 391HD came with a 4V Holley, all governor carbs. They have a tall tach-drive governor distributor and the truck-only steel front timing cover and dual thermostat housing.
A 330 has a bore of 3.875" and a 3.50" stroke. A 361 has a 4.05" bore and a 3.50" stroke and the 391 has a 4.05" bore and 3.79" stroke
359FT and 389FT were special fleet engines. U-haul was pushing to reduce costs, so Ford defined a low-cost formula for creating FT engines in special fleet applications sometime around 1973. The result was an engine with a cast iron crankshaft instead of the FT steel crank, and a governor installed (on all?) which reduced the redline about 500RPM below the governed 361FT and 391FT engines to prevent any opportunity for warranty issues resulting from the less robust crankshaft. The lower RPMs resulted in less horsepower output and longer life. U-haul bought them in quantity, and the rest is history.
FT/FE Parts Interchangeability


FT full-sump oil pan and special pickup, which works great on 2WD F100-350 or lifted 4x4s.


About the only things that are directly interchangeable are the connecting rods, lifters, rocker arm assemblies, pushrods, valve covers and oil pan. The steel timing chain cover and water pumps are different and won't interchange.
The rods, though they may have the truck number forged into it, are the same as 390/410/428 car rods, and are thus very desirable for econo-performance builds. 4-ring pistons use short connecting rods, 3-ring engines use long rods (later engines).
361s got the same block as the 391. The 391 prizes are the block, crank, and rods. The 361 only offers a block, and for high-winding maniacs - the sturdiest factory FE crank of all (used in Holman-Moody prepared 396FEs which oft times beat Petty in his 426 Hemi-powered monsters).
Block

The FT blocks are heavy-duty units and are virtually identical to the FE except that the distributor pilot hole is larger to allow for the 5/16" hex oil pump driveshaft. This means you'd have to install a bronze bushing in order to use a standard distributor with the 1/4" oil pump drive shaft, but there are bushings readily available (from Ford or the aftermarket). It's easy enough to do if you're doing other machine work on the block. You might also need to install a plug where the air compressor (for the air brakes) drains into the block. (The drain is low on the right side near the center of the block skirt.)
There is a very good chance the 361/391 FT block has the heavy cylinders which allow eventual boring to 428 numbers (including 428 +.060 overbores, sonic check for core shift permitting), though some FTs have been found with standard cylinder blocks that cannot handle the big overbore. You can do the Drill Bit Test to check the cylinder wall spacing and verify that a block can handle the overbore, as not every 361/391 block got the heavy cylinder jackets. The 330FT engine generally bores out to make a great 390 block, but it cannot be heavily overbored like most of the 361 and 391 blocks.
Another way of approximating cylinder wall thickness is to measure the block's cylinder wall thickness at the front of block's larger deck water jacket opening with a pair of outside (pincher-style) calipers . Use a Sharpie to mark the caliper's adjuster nut and then count the turns it takes you to get the caliper out of the block. Then spin the adjuster nut backward the same number of revolutions until it's adjusted back to where is was when it measured in the block. Then a quick comparison check with a micrometer and you're pretty close to knowing the actual size (+/- 0.002"-0.005").
Block markings

Ribs on the block only means it was cast after 1971, nothing more. The "C" or "CX", etc, on the back of the block is also period-specific, as is the "428" marking on the floor of the FT in the water jacket. Same with 427 text markings or crossbolt nubs.
The term "105" replaced the former term "352" as the standard FE casting mark in about 1973. At this time, casting of the FE block had approximately ceased at DIF and CF, and was almost completely taken up by Ford's all new foundry, MCC.
The "105" simply means it was cast at MCC (Ford's Michigan Casting Center). Thes does NOT indicate it has heavy cylinder walls, but it probably does have reinforced main bulkheads, since by 1973 most all FEs would only see pickup truck duty, and none would see the easier duty of cars.
There are some "105" blocks which have the heavier cylinder jackets commonly found with 361FT/391/406/428 blocks, but they are very much in the minority, and are most often found in Series 500 trucks and larger.
Cylinder Heads

The FT heads have the exhaust crossover setup completely different from FE units. (If you take the exhaust manifold off there will be 5 holes instead of 4.) The FT heads have 10 exhaust manifold bolts per head, whereas a car or light-duty truck engine has 8 exhaust manifold bolts per head. These heads are small-valve low-compression units that are unique to the FT series.
Intake/Exhaust Manifolds


FT exhaust manifolds - (Source)


The FT intake manifold will fit an FE, but you'd have to plug the FE cylinder head's exhaust crossover passages because they don't come close to lining up. It's debatable on whether it's worth the effort. There ARE 4V FT manifolds out there and that might be easier. But it depends on the thermostat arrangement your manifold has, since some (many?) of the FTs had a dual setup.
That exhaust crossover on the FT heads doesn't go into a port. Deleting it would be fairly easy and that will allow any FE intake to be used. It feeds straight through the head from extra holes in the center of the exhaust manifold, so if you have headers that passage is open and you only need to plug it at the intake manifold face to keep oil from leaking out or dirty air getting into the crankcase.
The distributor mounting hole in the intake manifold is the same size and location as an FE unit.
The exhaust manifolds are a ram's-horn design that will physically bolt up to an FE, but they contain an exhaust crossover port which would have to be welded shut to use on an FE engine. However, you might run into a side clearance problem when trying to use these on a smaller vehicle, since they angle out quite a bit.
Crankshaft

FT's have a forged steel crank with a 1-3/4" crank snout, while passenger car and light-duty truck FE's have a 1-3/8" snout, and therefore used a different balancer and pulley setup. (The dampers of the 361/391 will be counterweighted.) On a 391 crankshaft the first two counterweights (closest to the snout) will be in line with each other; if they are offset from each other about an inch, it's a 330HD-361. The 330MD wont have the large crank snout, and it wont be steel; 330HD and 361 engines will, and have a full-circle rear flange with no indexing notches or half-moon cutouts.
If trying to identify a crankshaft that's already removed, set it on it's rear flange and look down at the #1& #2 journals. If it looks like 'Mickey Mouse ears' or a hat it's a 361. If the 2nd, 3rd, & 4th journal is rounded or smooth, it's a 391.
The 391 crank is actually .002" longer in stroke than the 390/406/427 crank. The 390/406/427 is a 3.784" stroke +/- .004" tolerance. The 391 is 3.786" stroke +/- .004" tolerance. When rounded, the the 390/406/427 is sometimes shown to be 3.78" stroke and the 391 is sometimes shown to be 3.79". It's best, however, to carry strokes to three decimal places. Some references erroneously claim the 390/406/427 is a 3.781" stroke, but that is because they mistakenly assumed the stroke was based on 32nds of an inch increments.
To use the FT crankshaft in an FE block, the FT crankshaft's snout will need to be turned down to fit the standard FE timing cover that that you will need to use for your application. In addition, the crankshaft snout will need to be shortened, as some (or all) were longer to accommodate industrial accessory drives like air compressors for air brakes. After the end of the crankshaft is cut, you'll need to redrill the balancer bolt hole and cut a new keyway.
The rear of the FT crank is also different...the pilot hole is larger, as is the area to support the flywheel. Both require custom machining to be happy with passenger car applications. The flywheel centering flange is too tall and will need to be shortened. If you are going to use an automatic you need to have a reducing ring machined so the converter will fit in the end of the crank.
Be sure and have the assembly balanced as it may take heavy metal to come in.
<table> <tbody><tr> <td> <center>
<table class="gallery" cellpadding="0" cellspacing="0"> <caption>Rear Crankshaft Flange Blueprints - FT vs. FE</caption> <tbody><tr> <td>

<small>Fig. 01 - FT crankshaft rear flange blueprint - (source)</small>


</td> <td>

<small>Fig. 02 - FE crankshaft rear flange blueprint - (source)</small>


</td> </tr> </tbody></table></center> </td><td> <small>NOTE: The FT flange info comes from a Ford Industrial Power Products manual. The FE info comes from the factory 374cid NASCAR crank blueprint of 1966-67 which is based on the 3.300" stroke 332FE crank of 1958-59. The 374 and 354 NASCAR FEs of the mid 1960s allowed running less weight in the cars. The 396FE was a very successful 426 Hemi killer, and was based on a 427 block and 361 crank forging which was stroked to 3.514, had the rod journals widened to fit the NASCAR rod (wider bearings retain oil better under racing loads), and was crossdrilled.</small> </td></tr></tbody></table> While the 361-391 truck motors are externally-balanced like 410s & 428s, you can't use 428 flexplate on a 391 truck without rebalancing the whole engine. These have more counterweighting, as there were 4-ring pistons in many FT's, and they weigh more. Also, the placement of the counterweights is different for every stroke crank. You could make it work, but custom balancing is still required.
just joking

 

there is some amazing info in here! We have a 391 i cant seem to find much info on it so ibfigured id ask here...the vaccum port broke off in our carb spacer and we cant seem to find a replacement any ideas on how to delete this port or putting in a hole new carb? All these vaccum port start to get confusing 🙃